WorldWideScience

Sample records for singlet states symmetry-breakings

  1. Mirror symmetry, chiral symmetry breaking, and antihydrogen states in natural atomic H

    CERN Document Server

    Van Hooydonk, G

    2002-01-01

    Molecular band spectra reveal a left-right symmetry for atoms Yvan Hooydonk, Spectrochim. Acta A 56, 2273 (2000)¿. Intra-atomic left- right symmetry points to antiatom states and, to make sense, this must also show in line spectra. H Lyman ns singlets show a mirror plane at quantum number n/sub 0/= 1/2 pi . A symmetry-breaking oscillator (1- 1/2 pi /n)/sup 2/ means that some of these n states are antihydrogenic. This view runs ahead of CERN's antiproton decelerator project on antihydrogen. (7 refs).

  2. Viable dark matter via radiative symmetry breaking in a scalar singlet Higgs portal extension of the standard model.

    Science.gov (United States)

    Steele, T G; Wang, Zhi-Wei; Contreras, D; Mann, R B

    2014-05-02

    We consider the generation of dark matter mass via radiative electroweak symmetry breaking in an extension of the conformal standard model containing a singlet scalar field with a Higgs portal interaction. Generating the mass from a sequential process of radiative electroweak symmetry breaking followed by a conventional Higgs mechanism can account for less than 35% of the cosmological dark matter abundance for dark matter mass M(s)>80 GeV. However, in a dynamical approach where both Higgs and scalar singlet masses are generated via radiative electroweak symmetry breaking, we obtain much higher levels of dark matter abundance. At one-loop level we find abundances of 10%-100% with 106 GeVdark matter mass. The dynamical approach also predicts a small scalar-singlet self-coupling, providing a natural explanation for the astrophysical observations that place upper bounds on dark matter self-interaction. The predictions in all three approaches are within the M(s)>80 GeV detection region of the next generation XENON experiment.

  3. Reversible bridge-mediated excited-state symmetry breaking in stilbene-linked DNA dumbbells.

    Science.gov (United States)

    Lewis, Frederick D; Daublain, Pierre; Zhang, Ligang; Cohen, Boiko; Vura-Weis, Josh; Wasielewski, Michael R; Shafirovich, Vladimir; Wang, Qiang; Raytchev, Milen; Fiebig, Torsten

    2008-03-27

    The excited-state behavior of synthetic DNA dumbbells possessing stilbenedicarboxamide (Sa) linkers separated by short A-tracts or alternating A-T base-pair sequences has been investigated by means of fluorescence and transient absorption spectroscopy. Electronic excitation of the Sa chromophores results in conversion of a locally excited state to a charge-separated state in which one Sa is reduced and the other is oxidized. This symmetry-breaking process occurs exclusively via a multistep mechanism-hole injection followed by hole transport and hole trapping-even at short distances. Rate constants for charge separation are strongly distance-dependent at short distances but become less so at longer distances. Disruption of the A-tract by inversion of a single A-T base pair results in a pronounced decrease in both the rate constant and efficiency of charge separation. Hole trapping by Sa is highly reversible, resulting in rapid charge recombination that occurs via the reverse of the charge separation process: hole detrapping, hole transport, and charge return to regenerate the locally excited Sa singlet state. These results differ in several significant respects from those previously reported for guanine or stilbenediether as hole traps. Neither charge separation nor charge recombination occur via a single-step superexchange mechanism, and hole trapping is slower and detrapping faster when Sa serves as the electron donor. Both the occurrence of symmetry breaking and reversible hole trapping by a shallow trap in a DNA-based system are without precedent.

  4. Particle-Hole Symmetry Breaking in the Pseudogap State of Bi2201

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, M.; /SIMES, Stanford /Stanford U., Geballe Lab. /LBNL, ALS; He, R.-H.; /aff SIMES, Stanford /Stanford U., Geballe Lab.; Tanaka, K.; /aff SIMES, Stanford /Stanford U., Geballe Lab. /LBNL, ALS /Osaka U.; Testaud, J.P.; /SIMES, Stanford /Stanford U., Geballe Lab. /LBNL, ALS; Meevasana1, W.; Moore, R.G.; Lu, D.H.; /SIMES, Stanford /Stanford U., Geballe Lab.; Yao, H.; /SIMES, Stanford; Yoshida, Y.; Eisaki, H.; /AIST, Tsukuba; Devereaux, T.P.; /SIMES, Stanford /Stanford U., Geballe Lab.; Hussain, Z.; /LBNL, ALS; Shen, Z.-X.; /SIMES, Stanford /Stanford U., Geballe Lab.

    2011-08-19

    In conventional superconductors, a gap exists in the energy absorption spectrum only below the transition temperature (T{sub c}), corresponding to the energy price to pay for breaking a Cooper pair of electrons. In high-T{sub c} cuprate superconductors above T{sub c}, an energy gap called the pseudogap exists, and is controversially attributed either to pre-formed superconducting pairs, which would exhibit particle-hole symmetry, or to competing phases which would typically break it. Scanning tunnelling microscopy (STM) studies suggest that the pseudogap stems from lattice translational symmetry breaking and is associated with a different characteristic spectrum for adding or removing electrons (particle-hole asymmetry). However, no signature of either spatial or energy symmetry breaking of the pseudogap has previously been observed by angle-resolved photoemission spectroscopy (ARPES). Here we report ARPES data from Bi2201 which reveals both particle-hole symmetry breaking and dramatic spectral broadening indicative of spatial symmetry breaking without long range order, upon crossing through T* into the pseudogap state. This symmetry breaking is found in the dominant region of the momentum space for the pseudogap, around the so-called anti-node near the Brillouin zone boundary. Our finding supports the STM conclusion that the pseudogap state is a broken-symmetry state that is distinct from homogeneous superconductivity.

  5. Traces of Lorentz symmetry breaking in a hydrogen atom at ground state

    Energy Technology Data Exchange (ETDEWEB)

    Borges, L.H.C. [Universidade Federal do ABC, Centro de Ciencias Naturais e Humanas, Santo Andre, SP (Brazil); Barone, F.A. [IFQ-Universidade Federal de Itajuba, Itajuba, MG (Brazil)

    2016-02-15

    Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schroedinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector. (orig.)

  6. Traces of Lorentz symmetry breaking in a hydrogen atom at ground state

    International Nuclear Information System (INIS)

    Borges, L.H.C.; Barone, F.A.

    2016-01-01

    Some traces of a specific Lorentz symmetry breaking scenario in the ground state of the hydrogen atom are investigated. We use standard Rayleigh-Schroedinger perturbation theory in order to obtain the corrections to the ground state energy and the wave function. It is shown that an induced four-pole moment arises, due to the Lorentz symmetry breaking. The model considered is the one studied in Borges et al. (Eur Phys J C 74:2937, 2014), where the Lorentz symmetry is broken in the electromagnetic sector. (orig.)

  7. Bootstrap Dynamical Symmetry Breaking

    Directory of Open Access Journals (Sweden)

    Wei-Shu Hou

    2013-01-01

    Full Text Available Despite the emergence of a 125 GeV Higgs-like particle at the LHC, we explore the possibility of dynamical electroweak symmetry breaking by strong Yukawa coupling of very heavy new chiral quarks Q . Taking the 125 GeV object to be a dilaton with suppressed couplings, we note that the Goldstone bosons G exist as longitudinal modes V L of the weak bosons and would couple to Q with Yukawa coupling λ Q . With m Q ≳ 700  GeV from LHC, the strong λ Q ≳ 4 could lead to deeply bound Q Q ¯ states. We postulate that the leading “collapsed state,” the color-singlet (heavy isotriplet, pseudoscalar Q Q ¯ meson π 1 , is G itself, and a gap equation without Higgs is constructed. Dynamical symmetry breaking is affected via strong λ Q , generating m Q while self-consistently justifying treating G as massless in the loop, hence, “bootstrap,” Solving such a gap equation, we find that m Q should be several TeV, or λ Q ≳ 4 π , and would become much heavier if there is a light Higgs boson. For such heavy chiral quarks, we find analogy with the π − N system, by which we conjecture the possible annihilation phenomena of Q Q ¯ → n V L with high multiplicity, the search of which might be aided by Yukawa-bound Q Q ¯ resonances.

  8. Symmetry-breaking intramolecular charge transfer in the excited state of meso-linked BODIPY dyads

    KAUST Repository

    Whited, Matthew T.

    2012-01-01

    We report the synthesis and characterization of symmetric BODIPY dyads where the chromophores are attached at the meso position, using either a phenylene bridge or direct linkage. Both molecules undergo symmetry-breaking intramolecular charge transfer in the excited state, and the directly linked dyad serves as a visible-light-absorbing analogue of 9,9′-bianthryl.

  9. Ground state correlations associated with number symmetry breaking

    International Nuclear Information System (INIS)

    Oudih, M.R.; Benhamouda, N.; Fellah, M.; Allal, N.H.; Laboratoire de Physique Theorique, Algiers

    2004-01-01

    The ability of an exact particle-number projection to incorporate correlations in the ground state is investigated. The method is compared to the Lipkin-Nogami prescription and to the exact Richardson solution. (author)

  10. Long-range order and symmetry breaking in projected entangled-pair state models

    Science.gov (United States)

    Rispler, Manuel; Duivenvoorden, Kasper; Schuch, Norbert

    2015-10-01

    Projected entangled-pair states (PEPS) provide a framework for the construction of models where a single tensor gives rise to both Hamiltonian and ground state wave function on the same footing. A key problem is to characterize the behavior which emerges in the system in terms of the properties of the tensor, and thus of the Hamiltonian. In this paper, we consider PEPS models with Z2 on-site symmetry and study the occurrence of long-range order and spontaneous symmetry breaking. We show how long-range order is connected to a degeneracy in the spectrum of the PEPS transfer operator, and how the latter gives rise to spontaneous symmetry breaking under perturbations. We provide a succinct characterization of the symmetry-broken states in terms of the PEPS tensor, and find that using the symmetry-broken states we can derive a local entanglement Hamiltonian, thereby restoring locality of the entanglement Hamiltonian for all gapped phases.

  11. { Z}_N symmetry breaking in projected entangled pair state models

    Science.gov (United States)

    Rispler, Manuel; Duivenvoorden, Kasper; Schuch, Norbert

    2017-09-01

    We consider projected entangled pair state (PEPS) models with a global { Z}N symmetry, which are constructed from { Z}N -symmetric tensors and are thus { Z}N -invariant wavefunctions, and study the occurence of long-range order and symmetry breaking in these systems. First, we show that long-range order in those models is accompanied by a degeneracy in the so-called transfer operator of the system. We subsequently use this degeneracy to determine the nature of the symmetry broken states, i.e. those stable under arbitrary perturbations, and provide a succinct characterization in terms of the fixed points of the transfer operator (i.e. the different boundary conditions) in the individual symmetry sectors. We verify our findings numerically through the study of a { Z}3 -symmetric model, and show that the entanglement Hamiltonian derived from the symmetry broken states is quasi-local (unlike the one derived from the symmetric state), reinforcing the locality of the entanglement Hamiltonian for gapped phases.

  12. Polar Kerr effect studies of time reversal symmetry breaking states in heavy fermion superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Schemm, E.R., E-mail: eschemm@alumni.stanford.edu [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Levenson-Falk, E.M. [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Department of Physics, Stanford University, Stanford, CA 94305 (United States); Kapitulnik, A. [Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305 (United States); Department of Physics, Stanford University, Stanford, CA 94305 (United States); Department of Applied Physics, Stanford University, Stanford, CA 94305 (United States); Stanford Institute of Energy and Materials Science, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

    2017-04-15

    Highlights: • Polar Kerr effect (PKE) probes broken time-reversal symmetry (TRS) in superconductors. • Absence of PKE below Tc in CeCoIn{sub 5} is consistent with dx2-y2 order parameter symmetry. • PKE in the B phase of the multiphase superconductor UPt3 agrees with an E2u model. • Data on URu2Si2 show broken TRS and additional structure in the superconducting state. - Abstract: The connection between chiral superconductivity and topological order has emerged as an active direction in research as more instances of both have been identified in condensed matter systems. With the notable exception of {sup 3}He-B, all of the known or suspected chiral – that is to say time-reversal symmetry-breaking (TRSB) – superfluids arise in heavy fermion superconductors, although the vast majority of heavy fermion superconductors preserve time-reversal symmetry. Here we review recent experimental efforts to identify TRSB states in heavy fermion systems via measurement of polar Kerr effect, which is a direct consequence of TRSB.

  13. Electroweak symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Chanowitz, M.S.

    1990-09-01

    The Higgs mechanism is reviewed in its most general form, requiring the existence of a new symmetry-breaking force and associated particles, which need not however be Higgs bosons. The first lecture reviews the essential elements of the Higgs mechanism, which suffice to establish low energy theorems for the scattering of longitudinally polarized W and Z gauge bosons. An upper bound on the scale of the symmetry-breaking physics then follows from the low energy theorems and partial wave unitarity. The second lecture reviews particular models, with and without Higgs bosons, paying special attention to how the general features discussed in lecture 1 are realized in each model. The third lecture focuses on the experimental signals of strong WW scattering that can be observed at the SSC above 1 TeV in the WW subenergy, which will allow direct measurement of the strength of the symmetry-breaking force. 52 refs., 10 figs.

  14. Symmetry-breaking dynamics of the finite-size Lipkin-Meshkov-Glick model near ground state

    Science.gov (United States)

    Huang, Yi; Li, Tongcang; Yin, Zhang-qi

    2018-01-01

    We study the dynamics of the Lipkin-Meshkov-Glick (LMG) model with a finite number of spins. In the thermodynamic limit, the ground state of the LMG model with an isotropic Hamiltonian in the broken phase breaks to a mean-field ground state with a certain direction. However, when the spin number N is finite, the exact ground state is always unique and is not given by a classical mean-field ground state. Here, we prove that when N is large but finite, through a tiny external perturbation, a localized state which is close to a mean-field ground state can be prepared, which mimics spontaneous symmetry breaking. Also, we find the localized in-plane spin polarization oscillates with two different frequencies ˜O (1 /N ) , and the lifetime of the localized state is long enough to exhibit this oscillation. We numerically test the analytical results and find that they agree very well with each other. Finally, we link the phenomena to quantum time crystals and time quasicrystals.

  15. Final-state rescattering and SU(3) symmetry breaking in B→DK and B→DK* decays

    International Nuclear Information System (INIS)

    Xing, Z.Z.

    2003-01-01

    The first observation of the anti B 0 d →D 0 anti K 0 and anti B 0 d →D 0 anti K *0 transitions by the Belle Collaboration allows us to do a complete isospin analysis of the B→DK (*) decay modes. We find that their respective isospin phase shifts are very likely to lie in the ranges 37 circle ≤(φ 1 -φ 0 ) DK ≤63 circle (or around 50 circle ) and 25 circle ≤(φ 1 -φ 0 ) DK * ≤50 circle (or around 35 circle ), although the possibility (φ 1 -φ 0 ) DK = (φ 1 -φ 0 ) DK * = 0 circle cannot be ruled out at present. Thus significant final-state rescattering effects possibly exist in such exclusive vertical stroke ΔB vertical stroke = vertical stroke ΔC vertical stroke = vertical stroke ΔS vertical stroke =1 processes. We determine the spectator and color-suppressed spectator quark-diagram amplitudes of the B→DK and B→DK * decays, and compare them with the corresponding quark-diagram amplitudes of the B→Dπ and B→Dρ decays. The effects of SU(3) flavor symmetry breaking are in most cases understandable in the factorization approximation, which works for the individual isospin amplitudes. Very instructive predictions are also obtained for the branching fractions of rare anti B 0 d → anti D 0 anti K (*)0 , B - u → anti D 0 K (*)- and B - u →D - anti K (*)0 transitions. (orig.)

  16. Singlet Ground State Magnetism:

    DEFF Research Database (Denmark)

    Loidl, A.; Knorr, K.; Kjems, Jørgen

    1979-01-01

    The magneticGamma 1 –Gamma 4 exciton of the singlet ground state system TbP has been studied by inelastic neutron scattering above the antiferromagnetic ordering temperature. Considerable dispersion and a pronounced splitting was found in the [100] and [110] directions. Both the band width...... and the splitting increased rapidly as the transition temperature was approached in accordance with the predictions of the RPA-theory. The dispersion is analysed in terms of a phenomenological model using interactions up to the fourth nearest neighbour....

  17. Symmetry breaking and the geometry of reduced density matrices

    Science.gov (United States)

    Zauner, V.; Draxler, D.; Vanderstraeten, L.; Haegeman, J.; Verstraete, F.

    2016-11-01

    The concept of symmetry breaking and the emergence of corresponding local order parameters constitute the pillars of modern day many body physics. We demonstrate that the existence of symmetry breaking is a consequence of the geometric structure of the convex set of reduced density matrices of all possible many body wavefunctions. The surfaces of these convex bodies exhibit non-analyticities, which signal the emergence of symmetry breaking and of an associated order parameter and also show different characteristics for different types of phase transitions. We illustrate this with three paradigmatic examples of many body systems exhibiting symmetry breaking: the quantum Ising model, the classical q-state Potts model in two-dimensions at finite temperature and the ideal Bose gas in three-dimensions at finite temperature. This state based viewpoint on phase transitions provides a unique novel tool for studying exotic many body phenomena in quantum and classical systems.

  18. Quark diquark symmetry breaking

    International Nuclear Information System (INIS)

    Souza, M.M. de

    1980-01-01

    Assuming the baryons are made of quark-diquark pairs, the wave functions for the 126 allowed ground states are written. The quark creation and annihilations operators are generalized to describe the quark-diquark structure in terms of a parameter σ. Assuming that all quark-quark interactions are mediated by gluons transforming like an octet of vector mesons, the effective Hamiltonian and the baryon masses as constraint equations for the elements of the mass matrix is written. The symmetry is the SU(6) sub(quark)x SU(21) sub(diquark) broken by quark-quark interactions respectively invariant under U(6), U(2) sub(spin), U(3) and also interactions transforming like the eighth and the third components of SU(3). In the limit of no quark-diquark structure (σ = 0), the ground state masses is titted to within 1% of the experimental data, except for the Δ(1232), where the error is almost 2%. Expanding the decuplet mass equations in terms of σ and keeping terms only up to the second order, this error is reduced to 67%. (Author) [pt

  19. Strong Electroweak Symmetry Breaking

    CERN Document Server

    Grinstein, Benjamin

    2011-01-01

    Models of spontaneous breaking of electroweak symmetry by a strong interaction do not have fine tuning/hierarchy problem. They are conceptually elegant and use the only mechanism of spontaneous breaking of a gauge symmetry that is known to occur in nature. The simplest model, minimal technicolor with extended technicolor interactions, is appealing because one can calculate by scaling up from QCD. But it is ruled out on many counts: inappropriately low quark and lepton masses (or excessive FCNC), bad electroweak data fits, light scalar and vector states, etc. However, nature may not choose the minimal model and then we are stuck: except possibly through lattice simulations, we are unable to compute and test the models. In the LHC era it therefore makes sense to abandon specific models (of strong EW breaking) and concentrate on generic features that may indicate discovery. The Technicolor Straw Man is not a model but a parametrized search strategy inspired by a remarkable generic feature of walking technicolor,...

  20. Models of electroweak symmetry breaking

    CERN Document Server

    Pomarol, Alex

    2015-01-01

    This chapter present models of electroweak symmetry breaking arising from strongly interacting sectors, including both Higgsless models and mechanisms involving a composite Higgs. These scenarios have also been investigated in the framework of five-dimensional warped models that, according to the AdS/CFT correspondence, have a four-dimensional holographic interpretation in terms of strongly coupled field theories. We explore the implications of these models at the LHC.

  1. Natural electroweak symmetry breaking from scale invariant Higgs mechanism

    International Nuclear Information System (INIS)

    Farzinnia, Arsham; He, Hong-Jian; Ren, Jing

    2013-01-01

    We construct a minimal viable extension of the standard model (SM) with classical scale symmetry. Its scalar sector contains a complex singlet in addition to the SM Higgs doublet. The scale-invariant and CP-symmetric Higgs potential generates radiative electroweak symmetry breaking à la Coleman–Weinberg, and gives a natural solution to the hierarchy problem, free from fine-tuning. Besides the 125 GeV SM-like Higgs particle, it predicts a new CP-even Higgs (serving as the pseudo-Nambu–Goldstone boson of scale symmetry breaking) and a CP-odd scalar singlet (providing the dark matter candidate) at weak scale. We systematically analyze experimental constraints from direct LHC Higgs searches and electroweak precision tests, as well as theoretical bounds from unitarity, triviality and vacuum stability. We demonstrate the viable parameter space, and discuss implications for new Higgs searches at the upcoming LHC runs and the on-going direct detections of dark matter

  2. A model of intrinsic symmetry breaking

    International Nuclear Information System (INIS)

    Ge, Li; Li, Sheng; George, Thomas F.; Sun, Xin

    2013-01-01

    Different from the symmetry breaking associated with a phase transition, which occurs when the controlling parameter is manipulated across a critical point, the symmetry breaking presented in this Letter does not need parameter manipulation. Instead, the system itself suddenly undergoes symmetry breaking at a certain time during its evolution, which is intrinsic symmetry breaking. Through a polymer model, it is revealed that the origin of the intrinsic symmetry breaking is nonlinearity, which produces instability at the instance when the evolution crosses an inflexion point, where this instability breaks the original symmetry

  3. Dimensional reduction, monopoles and dynamical symmetry breaking

    Science.gov (United States)

    Dolan, Brian P.; Szabo, Richard J.

    2009-03-01

    We consider SU(2)-equivariant dimensional reduction of Yang-Mills-Dirac theory on manifolds of the form M × Bbb CP1, with emphasis on the effects of non-trivial magnetic flux on Bbb CP1. The reduction of Yang-Mills fields gives a chain of coupled Yang-Mills-Higgs systems on M with a Higgs potential leading to dynamical symmetry breaking, as a consequence of the monopole fields. The reduction of SU(2)-symmetric fermions gives massless Dirac fermions on M transforming under the low-energy gauge group with Yukawa couplings, again as a result of the internal U(1) fluxes. The tower of massive fermionic Kaluza-Klein states also has Yukawa interactions and admits a natural SU(2)-equivariant truncation by replacing Bbb CP1 with a fuzzy sphere. In this approach it is possible to obtain exactly massless chiral fermions in the effective field theory with Yukawa interactions, without any further requirements. We work out the spontaneous symmetry breaking patterns and determine the complete physical particle spectrum in a number of explicit examples.

  4. Effect of symmetry breaking on transition strength distributions

    International Nuclear Information System (INIS)

    Mitchell, G.E.; Shriner, J.F. Jr.

    2001-01-01

    The quantum numbers of over 100 states in 30 P have been determined from the ground state to 8 MeV. Previous measurements had provided complete spectroscopy in 26 Al. For these N=Z=odd nuclei, states of isospin T=0 and T=1 coexist at all energies. These spectra provide a unique opportunity to test the effect of symmetry breaking (of the approximate symmetry isospin) on the level statistics and on the transition strength distributions. The level statistics are strongly affected by the small symmetry breaking and the transition strength distributions differ from the Porter-Thomas distribution

  5. Hartree-Fock symmetry breaking around conical intersections

    Science.gov (United States)

    Jake, Lena C.; Henderson, Thomas M.; Scuseria, Gustavo E.

    2018-01-01

    We study the behavior of Hartree-Fock (HF) solutions in the vicinity of conical intersections. These are here understood as regions of a molecular potential energy surface characterized by degenerate or nearly degenerate eigenfunctions with identical quantum numbers (point group, spin, and electron numbers). Accidental degeneracies between states with different quantum numbers are known to induce symmetry breaking in HF. The most common closed-shell restricted HF instability is related to singlet-triplet spin degeneracies that lead to collinear unrestricted HF solutions. Adding geometric frustration to the mix usually results in noncollinear generalized HF (GHF) solutions, identified by orbitals that are linear combinations of up and down spins. Near conical intersections, we observe the appearance of coplanar GHF solutions that break all symmetries, including complex conjugation and time-reversal, which do not carry good quantum numbers. We discuss several prototypical examples taken from the conical intersection literature. Additionally, we utilize a recently introduced magnetization diagnostic to characterize these solutions, as well as a solution of a Jahn-Teller active geometry of H8+2.

  6. Symmetry breaking bifurcations of a current sheet

    International Nuclear Information System (INIS)

    Parker, R.D.; Dewar, R.L.; Johnson, J.L.

    1988-08-01

    Using a time evolution code with periodic boundary conditions, the viscoresistive hydromagnetic equations describing an initially static, planar current sheet with large Lundquist number have been evolved for times long enough to reach a steady state. A cosh 2 x resistivity model was used. For long periodicity lengths, L p , the resistivity gradient drives flows which cause forced reconnection at X point current sheets. Using L p as a bifurcation parameter, two new symmetry breaking bifurcations were found - a transition to an asymmetric island chain with nonzero, positive or negative phase velocity, and a transition to a static state with alternating large and small islands. These states are reached after a complex transient behavior which involves a competition between secondary current sheet instability and coalescence. 31 refs., 6 figs

  7. Curvature-induced symmetry breaking in nonlinear Schrodinger models

    DEFF Research Database (Denmark)

    Gaididei, Yuri Borisovich; Mingaleev, S. F.; Christiansen, Peter Leth

    2000-01-01

    We consider a curved chain of nonlinear oscillators and show that the interplay of curvature and nonlinearity leads to a symmetry breaking when an asymmetric stationary state becomes energetically more favorable than a symmetric stationary state. We show that the energy of localized states decrea...

  8. Spontaneous symmetry breaking, self-trapping, and Josephson oscillations

    CERN Document Server

    2013-01-01

    This volume collects a a number of contributions on spontaneous symmetry breaking. Current studies in this general field are going ahead at a full speed. The book present review chapters which give an overview on the major break throughs of recent years. It covers a number of different physical settings which are introduced when a nonlinearity is added to the underlying symmetric problems and its strength exceeds a certain critical value. The corresponding loss of symmetry, called spontaneous symmetry breaking, alias self-trapping into asymmetric states is extensively discussed in this book.

  9. Phenomenology of induced electroweak symmetry breaking

    International Nuclear Information System (INIS)

    Chang, Spencer; Galloway, Jamison; Luty, Markus A.; Salvioni, Ennio; Tsai, Yuhsin

    2015-01-01

    We study the phenomenology of models of electroweak symmetry breaking where the Higgs potential is destabilized by a tadpole arising from the coupling to an “auxiliary” Higgs sector. The auxiliary Higgs sector can be either perturbative or strongly coupled, similar to technicolor models. Since electroweak symmetry breaking is driven by a tadpole, the cubic and quartic Higgs couplings can naturally be significantly smaller than their values in the standard model. The theoretical motivation for these models is that they can explain the 125 GeV Higgs mass in supersymmetry without fine-tuning. The auxiliary Higgs sector contains additional Higgs states that cannot decouple from standard model particles, so these models predict a rich phenomenology of Higgs physics beyond the standard model. In this paper we analyze a large number of direct and indirect constraints on these models. We present the current constraints after the 8 TeV run of the LHC, and give projections for the sensitivity of the upcoming 14 TeV run. We find that the strongest constraints come from the direct searches A 0 →Zh, A 0 →tt-bar, with weaker constraints from Higgs coupling fits. For strongly-coupled models, additional constraints come from ρ + →WZ where ρ + is a vector resonance. Our overall conclusion is that a significant parameter space for such models is currently open, allowing values of the Higgs cubic coupling down to 0.4 times the standard model value for weakly coupled models and vanishing cubic coupling for strongly coupled models. The upcoming 14 TeV run of the LHC will stringently test this scenario and we identify several new searches with discovery potential for this class of models.

  10. Particle production from symmetry breaking after inflation

    CERN Document Server

    García-Bellido, J; Garcia-Bellido, Juan; Morales, Ester Ruiz

    2002-01-01

    Recent studies suggest that the process of symmetry breaking after inflation typically occurs very fast, within a single oscillation of the symmetry-breaking field, due to the spinodal growth of its long-wave modes, otherwise known as `tachyonic preheating'. In this letter we show how this sudden transition from the false to the true vacuum can induce a significant production of particles, bosons and fermions, coupled to the symmetry-breaking field. We find that this new mechanism of particle production in the early Universe may have interesting consequences for the origin of dark matter and the generation of the observed baryon asymmetry through leptogenesis.

  11. Time-reversal symmetry breaking in quantum billiards

    International Nuclear Information System (INIS)

    Schaefer, Florian

    2009-01-01

    The present doctoral thesis describes experimentally measured properties of the resonance spectra of flat microwave billiards with partially broken timereversal invariance induced by an embedded magnetized ferrite. A vector network analyzer determines the complex scattering matrix elements. The data is interpreted in terms of the scattering formalism developed in nuclear physics. At low excitation frequencies the scattering matrix displays isolated resonances. At these the effect of the ferrite on isolated resonances (singlets) and pairs of nearly degenerate resonances (doublets) is investigated. The hallmark of time-reversal symmetry breaking is the violation of reciprocity, i.e. of the symmetry of the scattering matrix. One finds that reciprocity holds in singlets; it is violated in doublets. This is modeled by an effective Hamiltonian of the resonator. A comparison of the model to the data yields time-reversal symmetry breaking matrix elements in the order of the level spacing. Their dependence on the magnetization of the ferrite is understood in terms of its magnetic properties. At higher excitation frequencies the resonances overlap and the scattering matrix elements fluctuate irregularly (Ericson fluctuations). They are analyzed in terms of correlation functions. The data are compared to three models based on random matrix theory. The model by Verbaarschot, Weidenmueller and Zirnbauer describes time-reversal invariant scattering processes. The one by Fyodorov, Savin and Sommers achieves the same for systems with complete time-reversal symmetry breaking. An extended model has been developed that accounts for partial breaking of time-reversal invariance. This extended model is in general agreement with the data, while the applicability of the other two models is limited. The cross-correlation function between forward and backward reactions determines the time-reversal symmetry breaking matrix elements of the Hamiltonian to up to 0.3 mean level spacings. Finally

  12. Time-reversal symmetry breaking in quantum billiards

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Florian

    2009-01-26

    The present doctoral thesis describes experimentally measured properties of the resonance spectra of flat microwave billiards with partially broken timereversal invariance induced by an embedded magnetized ferrite. A vector network analyzer determines the complex scattering matrix elements. The data is interpreted in terms of the scattering formalism developed in nuclear physics. At low excitation frequencies the scattering matrix displays isolated resonances. At these the effect of the ferrite on isolated resonances (singlets) and pairs of nearly degenerate resonances (doublets) is investigated. The hallmark of time-reversal symmetry breaking is the violation of reciprocity, i.e. of the symmetry of the scattering matrix. One finds that reciprocity holds in singlets; it is violated in doublets. This is modeled by an effective Hamiltonian of the resonator. A comparison of the model to the data yields time-reversal symmetry breaking matrix elements in the order of the level spacing. Their dependence on the magnetization of the ferrite is understood in terms of its magnetic properties. At higher excitation frequencies the resonances overlap and the scattering matrix elements fluctuate irregularly (Ericson fluctuations). They are analyzed in terms of correlation functions. The data are compared to three models based on random matrix theory. The model by Verbaarschot, Weidenmueller and Zirnbauer describes time-reversal invariant scattering processes. The one by Fyodorov, Savin and Sommers achieves the same for systems with complete time-reversal symmetry breaking. An extended model has been developed that accounts for partial breaking of time-reversal invariance. This extended model is in general agreement with the data, while the applicability of the other two models is limited. The cross-correlation function between forward and backward reactions determines the time-reversal symmetry breaking matrix elements of the Hamiltonian to up to 0.3 mean level spacings. Finally

  13. Dynamical study of symmetries: breaking and restauration

    International Nuclear Information System (INIS)

    Schuck, P.

    1986-09-01

    First symmetry breaking (spontaneous) is explained and the physical implication discussed for infinite systems. The relation with phase transitions is indicated. Then the specific aspects of symmetry breaking in finite systems is treated and illustrated in detail for the case of translational invariance with the help of an oversimplified but exactly solvable model. The method of projection (restauration of symmetry) is explained for the static case and also applied to the model. Symmetry breaking in the dynamical case and for instance the notion of a soft mode responsible for the symmetry breaking is discussed in the case of superfluidity and another exactly solvable model is introduced. The Goldstone mode is treated in detail. Some remarks on analogies with the breaking of chiral symmetry are made. Some recent developments in the theory of symmetry restauration are briefly outlined [fr

  14. Chiral symmetry and chiral-symmetry breaking

    International Nuclear Information System (INIS)

    Peskin, M.E.

    1982-12-01

    These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed

  15. The problem of symmetry breaking hierarchy

    International Nuclear Information System (INIS)

    Natale, A.A.

    1983-01-01

    The problem of symmetry breaking hierarchy in grand unified theories is discussed, proving the impossibility to get a big hierarchy of interactions, in a natural way within the framework of perturbation theory. (L.C.) [pt

  16. Phil Anderson and Gauge Symmetry Breaking

    Science.gov (United States)

    Witten, Edward

    In this article, I describe the celebrated paper that Phil Anderson wrote in 1962 with early contributions to the idea of gauge symmetry breaking in particle physics. To set the stage, I describe the work of Julian Schwinger to which Anderson was responding, and also some of Anderson's own work on superconductivity that provided part of the context. After describing Anderson's work I describe the later work of others, leading to the modern understanding of gauge symmetry breaking in weak interactions...

  17. Absence of spontaneous magnetism associated with a possible time-reversal symmetry breaking state beneath the surface of (110)-oriented YBa2Cu3O7-δ superconducting films

    Science.gov (United States)

    Saadaoui, H.; Salman, Z.; Prokscha, T.; Suter, A.; Huhtinen, H.; Paturi, P.; Morenzoni, E.

    2013-11-01

    We report the results of a search for spontaneous magnetism due to a time-reversal symmetry breaking phase in the superconducting state of (110)-oriented YBa2Cu3O7-δ films, expected near the surface in this geometry. Zero field and weak transverse field measurements performed using the low-energy muon spin rotation technique with muons implanted a few nm inside optimally doped YBa2Cu3O7-δ-(110) films show no appearance of spontaneous magnetic fields below the superconducting temperature down to 2.9 K. Our results give an upper limit of ˜0.02 mT for putative spontaneous internal fields.

  18. Workshop on electroweak symmetry breaking: proceedings

    International Nuclear Information System (INIS)

    Hinchliffe, I.

    1984-10-01

    A theoretical workshop on electroweak symmetry breaking at the Superconducting Supercollider was held at Lawrence Berkeley Laboratory, June 4-22, 1984. The purpose of the workshop was to focus theoretical attention on the ways in which experimentation at the SSC could reveal manifestations of the phenomenon responsible for electroweak symmetry breaking. This issue represents, at present, the most compelling scientific argument for the need to explore the energy region to be made accessible by the SSC, and a major aim of the workshop was to involve a broad cross section of particle theorists in the ongoing process of sharpening the requirements for both accelerator and detector design that will ensure detection and identification of meaningful signals, whatever form the electroweak symmetry breaking phenomenon should actually take. Separate entries were prepared for the data base for the papers presented

  19. Workshop on electroweak symmetry breaking: proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Hinchliffe, I. (ed.)

    1984-10-01

    A theoretical workshop on electroweak symmetry breaking at the Superconducting Supercollider was held at Lawrence Berkeley Laboratory, June 4-22, 1984. The purpose of the workshop was to focus theoretical attention on the ways in which experimentation at the SSC could reveal manifestations of the phenomenon responsible for electroweak symmetry breaking. This issue represents, at present, the most compelling scientific argument for the need to explore the energy region to be made accessible by the SSC, and a major aim of the workshop was to involve a broad cross section of particle theorists in the ongoing process of sharpening the requirements for both accelerator and detector design that will ensure detection and identification of meaningful signals, whatever form the electroweak symmetry breaking phenomenon should actually take. Separate entries were prepared for the data base for the papers presented.

  20. Isospin symmetry breaking in sd shell nuclei

    International Nuclear Information System (INIS)

    Lam, Y.W.

    2011-12-01

    In the thesis, we develop a microscopic approach to describe the isospin-symmetry breaking effects in sd-shell nuclei. The work is performed within the nuclear shell model. A realistic isospin-conserving Hamiltonian is perfected by a charge-dependent part consisting of the Coulomb interaction and Yukawa-type meson exchange potentials to model charge-dependent forces of nuclear origin. The extended database of the experimental isobaric mass multiplet equation coefficients was compiled during the thesis work and has been used in a fit of the Hamiltonian parameters. The constructed Hamiltonian provides an accurate theoretical description of the isospin mixing nuclear states. A specific behaviour of the IMME (Isobaric Multiplet Mass Equation) coefficients have been revealed. We present two important applications: (i) calculations of isospin-forbidden proton emission amplitudes, which is often of interest for nuclear astrophysics, and (ii) calculation on corrections to nuclear Fermi beta decay, which is crucial for the tests of fundamental symmetries of the weak interaction. (author)

  1. Introduction to symmetry breaking and spin

    International Nuclear Information System (INIS)

    Ng, J.N.

    1992-05-01

    These lectures form an elementary introduction to the physics of symmetry breaking and the role polarization experiments play in the study of gauge symmetry breaking. Included here is an introduction to testing the electroweak sector of the standard model to one-loop and the use of oblique corrections as a probe of new physics. The second part of the lectures consists of an introduction to multiple Higgs models as sources of spontaneous CP violation. A brief discussion of using spin measurements in meson decays to study these sources of CP violation is also included. (author)

  2. Continuum strong QCD: Confinement and dynamical chiral symmetry breaking

    International Nuclear Information System (INIS)

    Continuum strong QCD is the application of models and continuum quantum field theory to the study of phenomena in hadronic physics, which includes; e.g., the spectrum of QCD bound states and their interactions. Herein the author provides a Dyson-Schwinger equation perspective, focusing on qualitative aspects of confinement and dynamical chiral symmetry breaking in cold, sparse QCD, and also elucidating consequences of the axial-vector Ward-Takahashi identity and features of the heavy-quark limit

  3. Emergent Electroweak Symmetry Breaking with Composite W, Z Bosons

    CERN Document Server

    Cui, Yanou; Wells, James D

    2009-01-01

    We present a model of electroweak symmetry breaking in a warped extra dimension where electroweak symmetry is broken at the UV (or Planck) scale. An underlying conformal symmetry is broken at the IR (or TeV) scale generating masses for the electroweak gauge bosons without invoking a Higgs mechanism. By the AdS/CFT correspondence the W,Z bosons are identified as composite states of a strongly-coupled gauge theory, suggesting that electroweak symmetry breaking is an emergent phenomenon at the IR scale. The model satisfies electroweak precision tests with reasonable fits to the S and T parameter. In particular the T parameter is sufficiently suppressed since the model naturally admits a custodial SU(2) symmetry. The composite nature of the W,Z-bosons provide a novel possibility of unitarizing WW scattering via form factor suppression. Constraints from LEP and the Tevatron as well as discovery opportunities at the LHC are discussed for these composite electroweak gauge bosons.

  4. A new dynamics of electroweak symmetry breaking with classically scale invariance

    Energy Technology Data Exchange (ETDEWEB)

    Haba, Naoyuki [Graduate School of Science and Engineering, Shimane University, Matsue 690-8504 (Japan); Ishida, Hiroyuki, E-mail: ishida@riko.shimane-u.ac.jp [Graduate School of Science and Engineering, Shimane University, Matsue 690-8504 (Japan); Kitazawa, Noriaki [Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan); Yamaguchi, Yuya [Graduate School of Science and Engineering, Shimane University, Matsue 690-8504 (Japan); Department of Physics, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2016-04-10

    We propose a new dynamics of the electroweak symmetry breaking in a classically scale invariant version of the standard model. The scale invariance is broken by the condensations of additional fermions under a strong coupling dynamics. The electroweak symmetry breaking is triggered by negative mass squared of the elementary Higgs doublet, which is dynamically generated through the bosonic seesaw mechanism. We introduce a real pseudo-scalar singlet field interacting with additional fermions and Higgs doublet in order to avoid massless Nambu–Goldstone bosons from the chiral symmetry breaking in a strong coupling sector. We investigate the mass spectra and decay rates of these pseudo-Nambu–Goldstone bosons, and show they can decay fast enough without cosmological problems. We further show that our model can make the electroweak vacuum stable.

  5. A new dynamics of electroweak symmetry breaking with classically scale invariance

    Directory of Open Access Journals (Sweden)

    Naoyuki Haba

    2016-04-01

    Full Text Available We propose a new dynamics of the electroweak symmetry breaking in a classically scale invariant version of the standard model. The scale invariance is broken by the condensations of additional fermions under a strong coupling dynamics. The electroweak symmetry breaking is triggered by negative mass squared of the elementary Higgs doublet, which is dynamically generated through the bosonic seesaw mechanism. We introduce a real pseudo-scalar singlet field interacting with additional fermions and Higgs doublet in order to avoid massless Nambu–Goldstone bosons from the chiral symmetry breaking in a strong coupling sector. We investigate the mass spectra and decay rates of these pseudo-Nambu–Goldstone bosons, and show they can decay fast enough without cosmological problems. We further show that our model can make the electroweak vacuum stable.

  6. Dynamical Symmetry Breaking in RN Quantum Gravity

    Directory of Open Access Journals (Sweden)

    A. T. Kotvytskiy

    2011-01-01

    Full Text Available We show that in the RN gravitation model, there is no dynamical symmetry breaking effect in the formalism of the Schwinger-Dyson equation (in flat background space-time. A general formula for the second variation of the gravitational action is obtained from the quantum corrections hμν (in arbitrary background metrics.

  7. Symmetry breaking signaling mechanisms during cell polarization

    NARCIS (Netherlands)

    Bruurs, LJM

    2017-01-01

    Breaking of cellular symmetry in order to establish an apico-basal polarity axis initiates de novo formation of cell polarity. However, symmetry breaking provides a formidable challenge from a signaling perspective, because by definition no spatial cues are present to instruct axis establishment.

  8. Chiral symmetry and chiral-symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Peskin, M.E.

    1982-12-01

    These lectures concern the dynamics of fermions in strong interaction with gauge fields. Systems of fermions coupled by gauge forces have a very rich structure of global symmetries, which are called chiral symmetries. These lectures will focus on the realization of chiral symmetries and the causes and consequences of thier spontaneous breaking. A brief introduction to the basic formalism and concepts of chiral symmetry breaking is given, then some explicit calculations of chiral symmetry breaking in gauge theories are given, treating first parity-invariant and then chiral models. These calculations are meant to be illustrative rather than accurate; they make use of unjustified mathematical approximations which serve to make the physics more clear. Some formal constraints on chiral symmetry breaking are discussed which illuminate and extend the results of our more explicit analysis. Finally, a brief review of the phenomenological theory of chiral symmetry breaking is presented, and some applications of this theory to problems in weak-interaction physics are discussed. (WHK)

  9. Electroweak symmetry breaking beyond the Standard Model

    Indian Academy of Sciences (India)

    In this paper, two key issues related to electroweak symmetry breaking are addressed. First, how fine-tuned different models are that trigger this phenomenon? Second, even if a light Higgs boson exists, does it have to be necessarily elementary? After a brief introduction, the fine-tuning aspects of the MSSM, NMSSM, ...

  10. Unified gauge theories with spontaneous symmetry breaking

    International Nuclear Information System (INIS)

    MacDowell, S.W.

    1975-01-01

    Unified gauge theories with spontaneous symmetry breaking are studied with a view to renormalize quantum field theory. Georgi-Glashow and Weinberg-Salam models to unify weak and electromagnetic interactions are discussed in detail. Gauge theories of strong interactions are also considered [pt

  11. Symmetry breaking and restoration in gauge theories

    International Nuclear Information System (INIS)

    Natale, A.A.

    A review is made of the utilization of the Higgs mechanism in spontaneous symmetry breaking. It is shown that such as ideas came from an analogy with the superconductivity phenomenological theory based on a Ginzburg-Landau lagrangean. The symmetry restoration through the temperature influence is studied. (L.C.) [pt

  12. Symmetry-breaking instability in a prototypical driven granular gas.

    Science.gov (United States)

    Khain, Evgeniy; Meerson, Baruch

    2002-08-01

    Symmetry-breaking instability of a laterally uniform granular cluster (strip state) in a prototypical driven granular gas is investigated. The system consists of smooth hard disks in a two-dimensional box, colliding inelastically with each other and driven, at zero gravity, by a "thermal" wall. The limit of nearly elastic particle collisions is considered, and granular hydrodynamics with the Jenkins-Richman constitutive relations is employed. The hydrodynamic problem is completely described by two scaled parameters and the aspect ratio of the box. Marginal stability analysis predicts a spontaneous symmetry-breaking instability of the strip state, similar to that predicted recently for a different set of constitutive relations. If the system is big enough, the marginal stability curve becomes independent of the details of the boundary condition at the driving wall. In this regime, the density perturbation is exponentially localized at the elastic wall opposite the thermal wall. The short- and long-wavelength asymptotics of the marginal stability curves are obtained analytically in the dilute limit. The physics of the symmetry-breaking instability is discussed.

  13. Dual realizations of dynamical symmetry breaking

    International Nuclear Information System (INIS)

    Dudas, Emilian; Papineau, Chloe

    2006-01-01

    We show the infrared equivalence between a recently proposed model containing a six dimensional scalar field with a four-dimensional localized Higgs type potential and the four-dimensional Nambu-Jona-Lasinio (NJL) model. In the dual NJL description, the fermions are localized at the origin of a large two-dimensional compact space. Due to a classical running effect above the compactification scale, the four-fermion coupling of the NJL model increases from the cutoff scale down to the compactification scale, providing the large Fermi coupling needed for the dynamical symmetry breaking. We also present a string theory embedding of our field-theory construction. On more general grounds, our results suggest that 4d models with dynamical symmetry breaking can be given a higher dimensional description in terms of field theories with nontrivial boundary conditions in the internal space

  14. Electroweak symmetry breaking: Higgs/whatever

    International Nuclear Information System (INIS)

    Chanowitz, M.S.

    1989-01-01

    In the first of these two lectures the Higgs mechanism is reviewed in its most general form, which does not necessarily require the existence of Higgs bosons. The general consequences of the hypothesis that electroweak symmetry breaking is due to the Higgs mechanism are deduced just from gauge invariance and unitarity. In the second lecture the general properties are illustrated with three specific models: the Weinberg-Salam model, its minimal supersymmetric extension, and technicolor. The second lecture concludes with a discussion of the experiment signals for strong WW scattering, whose presence or absence will allow us to determine whether the symmetry breaking sector lies above or below 1 TeV. 57 refs

  15. Mechanochemical symmetry breaking in Hydra aggregates.

    Science.gov (United States)

    Mercker, Moritz; Köthe, Alexandra; Marciniak-Czochra, Anna

    2015-05-05

    Tissue morphogenesis comprises the self-organized creation of various patterns and shapes. Although detailed underlying mechanisms are still elusive in many cases, an increasing amount of experimental data suggests that chemical morphogen and mechanical processes are strongly coupled. Here, we develop and test a minimal model of the axis-defining step (i.e., symmetry breaking) in aggregates of the Hydra polyp. Based on previous findings, we combine osmotically driven shape oscillations with tissue mechanics and morphogen dynamics. We show that the model incorporating a simple feedback loop between morphogen patterning and tissue stretch reproduces a wide range of experimental data. Finally, we compare different hypothetical morphogen patterning mechanisms (Turing, tissue-curvature, and self-organized criticality). Our results suggest the experimental investigation of bigger (i.e., multiple head) aggregates as a key step for a deeper understanding of mechanochemical symmetry breaking in Hydra. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  16. Analysis of chiral symmetry breaking mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Xin-Heng, Guo [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Tao, Huang [Academia Sinica, Beijing, BJ (China). Inst. of High Energy Physics; Chuang, Wang

    1997-07-01

    The renormalization group invariant quark condensate {mu} is determinate both from the consistent equation for quark condensate in the chiral limit and from the Schwinger-Dyson (SD) equation improved by the intermediate range QCD force singular like {delta} (q) which is associated with the gluon condensate. The solutions of {mu} in these two equations are consistent. We also obtain the critical strong coupling constant {alpha}c above which chiral symmetry breaks in two approaches. The nonperturbative kernel of the SD equation makes {alpha}c smaller and {mu} bigger. An intuitive picture of the condensation above {alpha}c is discussed. In addition, with the help of the Slavnov-Taylor-Ward (STW) identity we derive the equations for the nonperturbative quark propagator from SD equation in the presence of the intermediate-range force is also responsible for dynamical chiral symmetry breaking. (author) 32 refs., 2 figs.

  17. Dynamics of Symmetry Breaking and Tachyonic Preheating

    CERN Document Server

    Felder, G; Greene, P B; Kofman, L A; Linde, Andrei D; Tkachev, Igor I; Felder, Gary; Garcia-Bellido, Juan; Greene, Patrick B.; Kofman, Lev; Linde, Andrei; Tkachev, Igor

    2001-01-01

    We reconsider the old problem of the dynamics of spontaneous symmetry breaking using 3d lattice simulations, and develop a theory of tachyonic preheating, which occurs due to the spinodal instability of the scalar field. Tachyonic preheating is so efficient that symmetry breaking typically completes within a single oscillation of the field distribution as it rolls towards the minimum of its effective potential. As an application of this theory we consider preheating in the hybrid inflation scenario, including SUSY-motivated F-term and D-term inflationary models. We show that preheating in hybrid inflation is typically tachyonic and the stage of oscillations of a homogeneous component of the scalar fields driving inflation ends after a single oscillation. Our results may also be relevant for the theory of the formation of disoriented chiral condensates in heavy ion collisions.

  18. Dynamical symmetry breaking in quantum field theories

    CERN Document Server

    Miransky, Vladimir A

    1993-01-01

    The phenomenon of dynamical symmetry breaking (DSB) in quantum field theory is discussed in a detailed and comprehensive way. The deep connection between this phenomenon in condensed matter physics and particle physics is emphasized. The realizations of DSB in such realistic theories as quantum chromodynamics and electroweak theory are considered. Issues intimately connected with DSB such as critical phenomenona and effective lagrangian approach are also discussed.

  19. Electroweak symmetry breaking via UV insensitive anomaly mediation

    International Nuclear Information System (INIS)

    Kitano, Ryuichiro; Kribs, Graham D.; Murayama, Hitoshi

    2004-01-01

    Anomaly mediation solves the supersymmetric flavor and CP problems. This is because the superconformal anomaly dictates that supersymmetry breaking is transmitted through nearly flavor-blind infrared physics that is highly predictive and UV insensitive. Slepton mass squareds, however, are predicted to be negative. This can be solved by adding D-terms for U(1) Y and U(1) B-L while retaining the UV insensitivity. In this paper we consider electroweak symmetry breaking via UV insensitive anomaly mediation in several models. For the minimal supersymmetric standard model we find a stable vacuum when tan β<1, but in this region the top Yukawa coupling blows up only slightly above the supersymmetry breaking scale. For the next-to-minimal supersymmetric standard model (NMSSM), we find a stable electroweak breaking vacuum but with a chargino that is too light. Replacing the cubic singlet term in the NMSSM superpotential with a term linear in the singlet we find a stable vacuum and viable spectrum. Most of the parameter region with correct vacua requires a large superpotential coupling, precisely what is expected in the 'Fat Higgs' model in which the superpotential is generated dynamically. We have therefore found the first viable UV complete, UV insensitive supersymmetry breaking model that solves the flavor and CP problems automatically: the Fat Higgs model with UV insensitive anomaly mediation. Moreover, the cosmological gravitino problem is naturally solved, opening up the possibility of realistic thermal leptogenesis

  20. Electromagnetic radiation under explicit symmetry breaking.

    Science.gov (United States)

    Sinha, Dhiraj; Amaratunga, Gehan A J

    2015-04-10

    We report our observation that radiation from a system of accelerating charges is possible only when there is explicit breaking of symmetry in the electric field in space within the spatial configuration of the radiating system. Under symmetry breaking, current within an enclosed area around the radiating structure is not conserved at a certain instant of time resulting in radiation in free space. Electromagnetic radiation from dielectric and piezoelectric material based resonators are discussed in this context. Finally, it is argued that symmetry of a resonator of any form can be explicitly broken to create a radiating antenna.

  1. Electroweak Symmetry Breaking (1/3)

    CERN Multimedia

    CERN. Geneva

    2012-01-01

    The focus of the lectures will be on the role of the Higgs boson in the mechanism of electroweak symmetry breaking, both in the Standard Model and in models of New Physics. In particular, I will discuss how a determination of its couplings to matter and gauge fields can give important information on the nature and origin of the Higgs boson. I will thus review the picture on Higgs couplings implied by the current experimental data and examine further interesting processes that can be measured in the future.

  2. Electroweak Symmetry Breaking (2/3)

    CERN Multimedia

    CERN. Geneva

    2012-01-01

    The focus of the lectures will be on the role of the Higgs boson in the mechanism of electroweak symmetry breaking, both in the Standard Model and in models of New Physics. In particular, I will discuss how a determination of its couplings to matter and gauge fields can give important information on the nature and origin of the Higgs boson. I will thus review the picture on Higgs couplings implied by the current experimental data and examine further interesting processes that can be measured in the future.

  3. Electroweak Symmetry Breaking (3/3)

    CERN Multimedia

    CERN. Geneva

    2012-01-01

    The focus of the lectures will be on the role of the Higgs boson in the mechanism of electroweak symmetry breaking, both in the Standard Model and in models of New Physics. In particular, I will discuss how a determination of its couplings to matter and gauge fields can give important information on the nature and origin of the Higgs boson. I will thus review the picture on Higgs couplings implied by the current experimental data and examine further interesting processes that can be measured in the future.

  4. Cosmoparticle physics of family symmetry breaking

    International Nuclear Information System (INIS)

    Khlopov, M.Yu.

    1993-07-01

    The foundations of both particle theory and cosmology are hidden at super energy scale and can not be tested by direct laboratory means. Cosmoparticle physics is developed to probe these foundations by the proper combination of their indirect effects, thus providing definite conclusions on their reliability. Cosmological and astrophysical tests turn to be complementary to laboratory searches of rare processes, induced by new physics, as it can be seen in the case of gauge theory of broken symmetry of quark and lepton families, ascribing to the hierarchy of the horizontal symmetry breaking the observed hierarchy of masses and the mixing between quark and lepton families. 36 refs

  5. Magnetic properties of singlet ground state systems

    International Nuclear Information System (INIS)

    Diederix, K.M.

    1979-01-01

    Experiments are described determining the properties of a magnetic system consisting of a singlet ground state. Cu(NO 3 ) 2 .2 1/2H 2 O has been studied which is a system of S = 1/2 alternating antiferromagnetic Heisenberg chains. The static properties, spin lattice relaxation time and field-induced antiferromagnetically ordered state measurements are presented. Susceptibility and magnetic cooling measurements of other compounds are summarised. (Auth.)

  6. Chiral symmetry breakings in supersymmetric QCD

    Energy Technology Data Exchange (ETDEWEB)

    Shinmura, Mamoru; Yamawaki, Koichi (Nagoya Univ. (Japan). Dept. of Physics)

    1984-05-01

    It is argued that spontaneous chiral symmetry breaking in supersymmetric QCD is due to the boson pair condensation instead of the fermion pair condensation in sharp contrast to the ordinary QCD. We further construct a low energy effective Lagrangian for supersymmetric QCD, which realizes the symmetry breaking, SU(N) sub(L) x SU(N) sub(R) x U(1) sub(V) x U(1) sub(X) down to SU(N) sub(V) x U(1) sub(V), in the massless limit. Our Lagrangian has no singular behaviour in the massless limit, supersymmetry being preserved independently of the quark mass m. It is shown that linear masses (instead of quadratic masses) of the pseudo-Nambu-Goldstone bosons are proportional to the quark mass and supersymmetric variants of Dashen's formulae are all saturated by the condensations -- O(m..lambda../sup 2/) and -- O (..lambda../sup 2/) for m -- 0.

  7. Symmetry Breaking in MILP Formulations for Unit Commitment Problems

    KAUST Repository

    Lima, Ricardo

    2015-12-11

    This paper addresses the study of symmetry in Unit Commitment (UC) problems solved by Mixed Integer Linear Programming (MILP) formulations, and using Linear Programming based Branch & Bound MILP solvers. We propose three sets of symmetry breaking constraints for UC MILP formulations exhibiting symmetry, and its impact on three UC MILP models are studied. The case studies involve the solution of 24 instances by three widely used models in the literature, with and without symmetry breaking constraints. The results show that problems that could not be solved to optimality within hours can be solved with a relatively small computational burden if the symmetry breaking constraints are assumed. The proposed symmetry breaking constraints are also compared with the symmetry breaking methods included in two MILP solvers, and the symmetry breaking constraints derived in this work have a distinct advantage over the methods in the MILP solvers.

  8. Spontaneous chiral symmetry breaking in early molecular networks

    Directory of Open Access Journals (Sweden)

    Markovitch Omer

    2010-05-01

    Full Text Available Abstract Background An important facet of early biological evolution is the selection of chiral enantiomers for molecules such as amino acids and sugars. The origin of this symmetry breaking is a long-standing question in molecular evolution. Previous models addressing this question include particular kinetic properties such as autocatalysis or negative cross catalysis. Results We propose here a more general kinetic formalism for early enantioselection, based on our previously described Graded Autocatalysis Replication Domain (GARD model for prebiotic evolution in molecular assemblies. This model is adapted here to the case of chiral molecules by applying symmetry constraints to mutual molecular recognition within the assembly. The ensuing dynamics shows spontaneous chiral symmetry breaking, with transitions towards stationary compositional states (composomes enriched with one of the two enantiomers for some of the constituent molecule types. Furthermore, one or the other of the two antipodal compositional states of the assembly also shows time-dependent selection. Conclusion It follows that chiral selection may be an emergent consequence of early catalytic molecular networks rather than a prerequisite for the initiation of primeval life processes. Elaborations of this model could help explain the prevalent chiral homogeneity in present-day living cells. Reviewers This article was reviewed by Boris Rubinstein (nominated by Arcady Mushegian, Arcady Mushegian, Meir Lahav (nominated by Yitzhak Pilpel and Sergei Maslov.

  9. Passive appendages generate drift through symmetry breaking

    Science.gov (United States)

    Lācis, U.; Brosse, N.; Ingremeau, F.; Mazzino, A.; Lundell, F.; Kellay, H.; Bagheri, S.

    2014-10-01

    Plants and animals use plumes, barbs, tails, feathers, hairs and fins to aid locomotion. Many of these appendages are not actively controlled, instead they have to interact passively with the surrounding fluid to generate motion. Here, we use theory, experiments and numerical simulations to show that an object with a protrusion in a separated flow drifts sideways by exploiting a symmetry-breaking instability similar to the instability of an inverted pendulum. Our model explains why the straight position of an appendage in a fluid flow is unstable and how it stabilizes either to the left or right of the incoming flow direction. It is plausible that organisms with appendages in a separated flow use this newly discovered mechanism for locomotion; examples include the drift of plumed seeds without wind and the passive reorientation of motile animals.

  10. Passive appendages aid locomotion through symmetry breaking

    Science.gov (United States)

    Bagheri, Shervin; Lacis, Ugis; Mazzino, Andrea; Kellay, Hamid; Brosse, Nicolas; Lundell, Fredrik; Ingremeau, Francois

    2014-11-01

    Plants and animals use plumes, barbs, tails, feathers, hairs, fins, and other types of appendages to aid locomotion. Despite their enormous variation, passive appendages may contribute to locomotion by exploiting the same physical mechanism. We present a new mechanism that applies to body appendages surrounded by a separated flow, which often develops behind moving bodies larger than a few millimeters. We use theory, experiments, and numerical simulations to show that bodies with protrusions turn and drift by exploiting a symmetry-breaking instability similar to the instability of an inverted pendulum. Our model explains why the straight position of an appendage in flowing fluid is unstable and how it stabilizes either to the left or right of the incoming fluid flow direction. The discovery suggests a new mechanism of locomotion that may be relevant for certain organisms; for example, how plumed seeds may drift without wind and how motile animals may passively reorient themselves.

  11. Symmetry breaking: The standard model and superstrings

    International Nuclear Information System (INIS)

    Gaillard, M.K.

    1988-01-01

    The outstanding unresolved issue of the highly successful standard model is the origin of electroweak symmetry breaking and of the mechanism that determines its scale, namely the vacuum expectation value (vev)v that is fixed by experiment at the value v = 4m//sub w//sup 2///g 2 = (√2G/sub F/)/sup /minus/1/ ≅ 1/4 TeV. In this talk I will discuss aspects of two approaches to this problem. One approach is straightforward and down to earth: the search for experimental signatures, as discussed previously by Pierre Darriulat. This approach covers the energy scales accessible to future and present laboratory experiments: roughly (10/sup /minus/9/ /minus/ 10 3 )GeV. The second approach involves theoretical speculations, such as technicolor and supersymmetry, that attempt to explain the TeV scale. 23 refs., 5 figs

  12. Symmetry breaking: The standard model and superstrings

    Energy Technology Data Exchange (ETDEWEB)

    Gaillard, M.K.

    1988-08-31

    The outstanding unresolved issue of the highly successful standard model is the origin of electroweak symmetry breaking and of the mechanism that determines its scale, namely the vacuum expectation value (vev)v that is fixed by experiment at the value v = 4m//sub w//sup 2///g/sup 2/ = (..sqrt..2G/sub F/)/sup /minus/1/ approx. = 1/4 TeV. In this talk I will discuss aspects of two approaches to this problem. One approach is straightforward and down to earth: the search for experimental signatures, as discussed previously by Pierre Darriulat. This approach covers the energy scales accessible to future and present laboratory experiments: roughly (10/sup /minus/9/ /minus/ 10/sup 3/)GeV. The second approach involves theoretical speculations, such as technicolor and supersymmetry, that attempt to explain the TeV scale. 23 refs., 5 figs.

  13. Physical Model of Cellular Symmetry Breaking

    Science.gov (United States)

    van der Gucht, Jasper; Sykes, Cécile

    2009-01-01

    Cells can polarize in response to external signals, such as chemical gradients, cell–cell contacts, and electromagnetic fields. However, cells can also polarize in the absence of an external cue. For example, a motile cell, which initially has a more or less round shape, can lose its symmetry spontaneously even in a homogeneous environment and start moving in random directions. One of the principal determinants of cell polarity is the cortical actin network that underlies the plasma membrane. Tension in this network generated by myosin motors can be relaxed by rupture of the shell, leading to polarization. In this article, we discuss how simplified model systems can help us to understand the physics that underlie the mechanics of symmetry breaking. PMID:20066077

  14. A (critical) overview of electroweak symmetry breaking

    International Nuclear Information System (INIS)

    Csaki, Csaba

    2010-01-01

    This presentation discusses the following points: The standard Higgs, big vs. little hierarchy; Electroweak Symmetry Breaking in supersymmetry and little hierarchy of Minimal Supersymmetric Standard Model (MSSM): Buried Higgs, Bigger quartic (D-terms, Next-to-Minimal Supersymmetric Standard Model (NMSSM), fat Higgs,..); Strong dynamics and related models: Technicolor, Monopole condensate, Warped extra dimensions, Realistic RS, Higgs-less, Composite Higgs, Little Higgs. In summary, we do not understand how Higgs is light and still no trace of new physics. In Supersymmetry (SUSY) it calls for extension of MSSM. In strong dynamics models: electroweak penguin (EWP) usually issue (Warped extra dimension - composite Higgs, Higgs-less, Little Higgs, Technicolor, monopole condensation,..). None of them is fully convincing but LHC should settle these

  15. Lie-algebra approach to symmetry breaking

    International Nuclear Information System (INIS)

    Anderson, J.T.

    1981-01-01

    A formal Lie-algebra approach to symmetry breaking is studied in an attempt to reduce the arbitrariness of Lagrangian (Hamiltonian) models which include several free parameters and/or ad hoc symmetry groups. From Lie algebra it is shown that the unbroken Lagrangian vacuum symmetry can be identified from a linear function of integers which are Cartan matrix elements. In broken symmetry if the breaking operators form an algebra then the breaking symmetry (or symmetries) can be identified from linear functions of integers characteristic of the breaking symmetries. The results are applied to the Dirac Hamiltonian of a sum of flavored fermions and colored bosons in the absence of dynamical symmetry breaking. In the partially reduced quadratic Hamiltonian the breaking-operator functions are shown to consist of terms of order g 2 , g, and g 0 in the color coupling constants and identified with strong (boson-boson), medium strong (boson-fermion), and fine-structure (fermion-fermion) interactions. The breaking operators include a boson helicity operator in addition to the familiar fermion helicity and ''spin-orbit'' terms. Within the broken vacuum defined by the conventional formalism, the field divergence yields a gauge which is a linear function of Cartan matrix integers and which specifies the vacuum symmetry. We find that the vacuum symmetry is chiral SU(3) x SU(3) and the axial-vector-current divergence gives a PCAC -like function of the Cartan matrix integers which reduces to PCAC for SU(2) x SU(2) breaking. For the mass spectra of the nonets J/sup P/ = 0 - ,1/2 + ,1 - the integer runs through the sequence 3,0,-1,-2, which indicates that the breaking subgroups are the simple Lie groups. Exact axial-vector-current conservation indicates a breaking sum rule which generates octet enhancement. Finally, the second-order breaking terms are obtained from the second-order spin tensor sum of the completely reduced quartic Hamiltonian

  16. Gauge principle, vector-meson dominance, and spontaneous symmetry breaking

    International Nuclear Information System (INIS)

    Nambu, Yoichiro

    1989-01-01

    The author concentrates on certain theoretical developments of the late 1950s which are concerned with the meaning and role of symmetries and symmetry breaking, and especially work done in Chicago, and notes his own involvement in this debate. He worked on symmetry-breaking in superconductivity, using a four-fermion interaction model. (UK)

  17. Symmetry breaking in collective honeybee foraging: a simulation study

    NARCIS (Netherlands)

    Vries, Han de; Biesmeijer, J.C.

    2002-01-01

    Symmetry breaking is the phenomenon that the numbers of foragers exploiting two equally profitable food sources will diverge. This phenomenon has been investigated in ants [1,4,5], but hardly in honeybees. It is even not clear whether in honeybees symmetry breaking can occur [3, p.190]. We present

  18. Physical pictures of symmetry breaking in quenched QED4

    International Nuclear Information System (INIS)

    Kogut, J.B.; Argonne National Lab., IL

    1989-01-01

    We discuss 'collapse of the wavefunction' as the phenomenon underlying chiral symmetry breaking in quenched QED4. The 1/r singularity in the 'collapsed' qanti q wavefunction causes 'catalyzed symmetry breaking' which is the field theoretic analog of 'monopole induced proton decay'. The evasion of mean field exponents by the quenched theory's chiral phase transition is emphasized. (orig.)

  19. Electroweak symmetry breaking and Higgs physics: basic concepts

    International Nuclear Information System (INIS)

    Gomez-Bock, M; Mondragon, M; Muehlleitner, M; Noriega-Papaqui, R; Pedraza, I; Spira, M; Zerwas, P M

    2005-01-01

    We present an introduction to the basic concepts of electroweak symmetry breaking and Higgs physics within the Standard Model and its sypersymmetric extensions. A brief overview will also be given on alternative mechanisms of symmetry breaking. In addition to the theoretical basis, the present experimental status of Higgs physics and implications for future experiments at the LHC and e + e - linear colliders are discussed

  20. Implications of dynamical symmetry breaking for high energy experiments

    International Nuclear Information System (INIS)

    Ali, A.

    1981-06-01

    A scenario of dynamical symmetry breaking as an alternative to the canonical Higgs mechanism with elementary spin-O fields is described, and its implications for high energy experiments contrasted with those of the canonical theory. The potential role of e + e - annihilation physics in unravelling the nature of spontaneous symmetry breaking is emphasized. (orig.)

  1. Effective potential and spontaneous symmetry breaking in the noncommutative φ6 model

    International Nuclear Information System (INIS)

    Barbosa, G.D.

    2004-01-01

    We study the conditions for spontaneous symmetry breaking of the (2+1)-dimensional noncommutative φ 6 model in the small-θ limit. In this regime, considering the model as a cutoff theory, it is reasonable to assume translational invariance as a property of the vacuum state and study the conditions for spontaneous symmetry breaking by an effective potential analysis. An investigation of up to the two-loop level reveals that noncommutative effects can modify drastically the shape of the effective potential. Under reasonable conditions, the nonplanar sector of the theory can become dominant and induce symmetry breaking for values of the mass and coupling constants not reached by the commutative counterpart

  2. On the gauge dependence of spontaneous symmetry breaking in gauge theories

    International Nuclear Information System (INIS)

    Nielsen, N.K.

    1975-01-01

    The Ward-Takahashi identities for scalar electrodynamics in Fermi gauges are shown to imply a homogeneous first-order partial differential equation for the effective potential involving only the gauge parameter and the external scalar field. Spontaneous symmetry breaking is consequently a gauge-invariant phenomenon. Also observable quantities, including masses, physical coupling constants, and S-matrix elements, of a theory with spontaneous symmetry breaking are found to be invariant, if a change in the gauge parameter is accompanied by a suitable change in the ground-state expectation value of the scalar field. The generalization to a non-Abelian gauge theory is briefly indicated. (Auth.)

  3. Golden Probe of Electroweak Symmetry Breaking

    CERN Document Server

    Chen, Yi; Spiropulu, Maria; Stolarski, Daniel; Vega-Morales, Roberto

    2016-12-09

    The ratio of the Higgs couplings to $WW$ and $ZZ$ pairs, $\\lambda_{WZ}$, is a fundamental parameter in electroweak symmetry breaking as well as a measure of the (approximate) custodial symmetry possessed by the gauge boson mass matrix. We show that Higgs decays to four leptons are sensitive, via tree level/1-loop interference effects, to both the magnitude and, in particular, overall sign of $\\lambda_{WZ}$. Determining this sign requires interference effects, as it is nearly impossible to measure with rate information. Furthermore, simply determining the sign effectively establishes the custodial representation of the Higgs boson. We find that $h\\to4\\ell$ ($4\\ell \\equiv 2e2\\mu, 4e, 4\\mu$) decays have excellent prospects of directly establishing the overall sign at a high luminosity 13 TeV LHC. We also examine the ultimate LHC sensitivity in $h\\to4\\ell$ to the magnitude of $\\lambda_{WZ}$. Our results are independent of other measurements of the Higgs boson couplings and, in particular, largely free of assumpti...

  4. Electroweak symmetry breaking: Higgs/whatever

    International Nuclear Information System (INIS)

    Chanowitz, M.S.

    1990-01-01

    In these two lectures the author discusses electroweak symmetry breaking from a general perspective, stressing properties that are model independent and follow just from the assumption that the electroweak interactions are described by a spontaneously broken gauge theory. This means he assumes the Higgs mechanism though not necessarily the existence of Higgs bosons. The first lecture presents the general framework of a spontaneously broken gauge theory: (1) the Higgs mechanism sui generis, with or without Higgs boson(s) and (2) the implications of symmetry and unitarity for the mass scale and interaction strength of the new physics that the Higgs mechanism requires. In addition he reviews a softer theoretical argument based on the naturalness problem which leads to a prejudice against Higgs bosons unless they are supersymmetric. This is a prejudice, not a theorem, and it could be overturned in the future by a clever new idea. In the second lecture he illustrates the general framework by reviewing some specific models: (1) the Weinberg-Salam model of the Higgs sector; (2) the minimal supersymmetric extension of the Weinberg-Salam model; and (3) technicolor as an example of the Higgs mechanism without Higgs bosons. He concludes the second lecture with a discussion of strong WW scattering that must occur if L SB lives above 1 TeV. In particular he describes some of the experimental signals and backgrounds at the SSC. 57 refs., 12 figs

  5. Supersymmetry in a sector of Higgsless electroweak symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Knochel, Alexander Karl

    2009-05-11

    In this thesis we have investigated phenomenological implications which arise for cosmology and collider physics when the electroweak symmetry breaking sector of warped higgsless models is extended to include warped supersymmetry with conserved R parity. The goal was to find the simplest supersymmetric extension of these models which still has a realistic light spectrum including a viable dark matter candidate. To accomplish this, we have used the same mechanism which is already at work for symmetry breaking in the electroweak sector to break supersymmetry as well, namely symmetry breaking by boundary conditions. While supersymmetry in five dimensions contains four supercharges and is therefore directly related to 4D N=2 supersymmetry, half of them are broken by the background leaving us with ordinary N=1 theory in the massless sector after Kaluza-Klein expansion. We thus use boundary conditions to model the effects of a breaking mechanism for the remaining two supercharges. The simplest viable scenario to investigate is a supersymmetric bulk and IR brane without supersymmetry on the UV brane. Even though parts of the light spectrum are effectively projected out by this mechanism, we retain the rich phenomenology of complete N=2 supermultiplets in the Kaluza-Klein sector. While the light supersymmetric spectrum consists of electroweak gauginos which get their O(100 GeV) masses from IR brane electroweak symmetry breaking, the light gluinos and squarks are projected out on the UV brane. The neutralinos, as mass eigenstates of the neutral bino-wino sector, are automatically the lightest gauginos, making them LSP dark matter candidates with a relic density that can be brought to agreement withWMAP measurements without extensive tuning of parameters. For chargino masses close to the experimental lower bounds at around m{sub {chi}{sup +}}{approx}100.. 110 GeV, the dark matter relic density points to LSP masses of around m{sub {chi}}{approx}90 GeV. At the LHC, the

  6. Supersymmetry in a sector of Higgsless electroweak symmetry breaking

    International Nuclear Information System (INIS)

    Knochel, Alexander Karl

    2009-01-01

    In this thesis we have investigated phenomenological implications which arise for cosmology and collider physics when the electroweak symmetry breaking sector of warped higgsless models is extended to include warped supersymmetry with conserved R parity. The goal was to find the simplest supersymmetric extension of these models which still has a realistic light spectrum including a viable dark matter candidate. To accomplish this, we have used the same mechanism which is already at work for symmetry breaking in the electroweak sector to break supersymmetry as well, namely symmetry breaking by boundary conditions. While supersymmetry in five dimensions contains four supercharges and is therefore directly related to 4D N=2 supersymmetry, half of them are broken by the background leaving us with ordinary N=1 theory in the massless sector after Kaluza-Klein expansion. We thus use boundary conditions to model the effects of a breaking mechanism for the remaining two supercharges. The simplest viable scenario to investigate is a supersymmetric bulk and IR brane without supersymmetry on the UV brane. Even though parts of the light spectrum are effectively projected out by this mechanism, we retain the rich phenomenology of complete N=2 supermultiplets in the Kaluza-Klein sector. While the light supersymmetric spectrum consists of electroweak gauginos which get their O(100 GeV) masses from IR brane electroweak symmetry breaking, the light gluinos and squarks are projected out on the UV brane. The neutralinos, as mass eigenstates of the neutral bino-wino sector, are automatically the lightest gauginos, making them LSP dark matter candidates with a relic density that can be brought to agreement withWMAP measurements without extensive tuning of parameters. For chargino masses close to the experimental lower bounds at around m χ + ∼100.. 110 GeV, the dark matter relic density points to LSP masses of around m χ ∼90 GeV. At the LHC, the standard particle content of our

  7. Ras activation and symmetry breaking during Dictyostelium chemotaxis

    NARCIS (Netherlands)

    Kortholt, Arjan; Keizer-Gunnink, Ineke; Kataria, Rama; Van Haastert, Peter J. M.

    2013-01-01

    Central to chemotaxis is the molecular mechanism by which a shallow spatial gradient of chemoattractant induces symmetry breaking of activated signaling molecules. Previously, we have used Dictyostelium mutants to investigate the minimal requirements for chemotaxis, and identified a basal signaling

  8. Mirror Symmetry Breaking by Chirality Synchronisation in Liquids and Liquid Crystals of Achiral Molecules.

    Science.gov (United States)

    Tschierske, Carsten; Ungar, Goran

    2016-01-04

    Spontaneous mirror symmetry breaking is an efficient way to obtain homogeneously chiral agents, pharmaceutical ingredients and materials. It is also in the focus of the discussion around the emergence of uniform chirality in biological systems. Tremendous progress has been made by symmetry breaking during crystallisation from supercooled melts or supersaturates solutions and by self-assembly on solid surfaces and in other highly ordered structures. However, recent observations of spontaneous mirror symmetry breaking in liquids and liquid crystals indicate that it is not limited to the well-ordered solid state. Herein, progress in the understanding of a new dynamic mode of symmetry breaking, based on chirality synchronisation of transiently chiral molecules in isotropic liquids and in bicontinuous cubic, columnar, smectic and nematic liquid crystalline phases is discussed. This process leads to spontaneous deracemisation in the liquid state under thermodynamic control, giving rise to long-term stable symmetry-broken fluids, even at high temperatures. These fluids form conglomerates that are capable of extraordinary strong chirality amplification, eventually leading to homochirality and providing a new view on the discussion of emergence of uniform chirality in prebiotic systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Lorentz symmetry breaking effects on relativistic EPR correlations

    Energy Technology Data Exchange (ETDEWEB)

    Belich, H. [Universidade Federal do Espirito Santo, Departamento de Fisica e Quimica, Vitoria, ES (Brazil); Furtado, C.; Bakke, K. [Universidade Federal da Paraiba, Departamento de Fisica, Caixa Postal 5008, Joao Pessoa, PB (Brazil)

    2015-09-15

    Lorentz symmetry breaking effects on relativistic EPR (Einstein-Podolsky-Rosen) correlations are discussed. From the modified Maxwell theory coupled to gravity, we establish a possible scenario of the Lorentz symmetry violation and write an effective metric for the Minkowski spacetime. Then we obtain the Wigner rotation angle via the Fermi-Walker transport of spinors and consider the WKB (Wentzel-Kramers-Brillouin) approximation in order to study the influence of Lorentz symmetry breaking effects on the relativistic EPR correlations. (orig.)

  10. Concepts of electroweak symmetry breaking and Higgs physics

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Bock, M. [Benemerita Univ., Puebla (Mexico). Inst. de Fisica; Mondragon, M. [Universidad Nacional Autonoma de Mexico, Mexico City (Mexico). Inst. de Fisica; Muehlleitner, M. [Laboratoire d' Annecy-Le-Vieux de Physique Theorique, 74 (France)]|[CERN - European Organization for Nuclear Research, Geneva (Switzerland). Theory Div.; Spira, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Zerwas, P.M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)]|[RWTH Aachen (Germany). Inst. Theor. Physik E]|[Univ. Paris- Sud, Orsay (France). Laboratoire de Physique Theorique

    2007-12-15

    We present an introduction to the basic concepts of electroweak symmetry breaking and Higgs physics within the Standard Model and its supersymmetric extensions. A brief overview will also be given on alternative mechanisms of electroweak symmetry breaking. In addition to the theoretical basis, the present experimental status of Higgs physics and prospects at the Tevatron, the LHC and e{sup +}e{sup -} linear colliders are discussed. (orig.)

  11. Dynamical symmetry breaking in models with strong Yukawa interactions

    Czech Academy of Sciences Publication Activity Database

    Beneš, Petr

    2012-01-01

    Roč. 62, 1-2 (2012), s. 1-274 ISSN 0323-0465 R&D Projects: GA ČR GA202/06/0734; GA MŠk LA08015 Institutional support: RVO:61389005 Keywords : spontaneus symmetry breaking * Gauge symmetries * nonperturbative techniques * radiative symmetry breaking * Quark and lepton masses * Cabibbo-Kobayashi-Maskawa matrix elements * extensions of electroweak Higgs sector Subject RIV: BE - Theoretical Physics Impact factor: 1.333, year: 2012

  12. Concepts of electroweak symmetry breaking and Higgs physics

    International Nuclear Information System (INIS)

    Gomez-Bock, M.; Zerwas, P.M.; RWTH Aachen; Univ. Paris- Sud, Orsay

    2007-12-01

    We present an introduction to the basic concepts of electroweak symmetry breaking and Higgs physics within the Standard Model and its supersymmetric extensions. A brief overview will also be given on alternative mechanisms of electroweak symmetry breaking. In addition to the theoretical basis, the present experimental status of Higgs physics and prospects at the Tevatron, the LHC and e + e - linear colliders are discussed. (orig.)

  13. Covalent bond symmetry breaking and protein secondary structure

    OpenAIRE

    Lundgren, Martin; Niemi, Antti J.

    2011-01-01

    Both symmetry and organized breaking of symmetry have a pivotal r\\^ole in our understanding of structure and pattern formation in physical systems, including the origin of mass in the Universe and the chiral structure of biological macromolecules. Here we report on a new symmetry breaking phenomenon that takes place in all biologically active proteins, thus this symmetry breaking relates to the inception of life. The unbroken symmetry determines the covalent bond geometry of a sp3 hybridized ...

  14. Symmetry Breaking in the Parton Distribution Functions of the Nucleon

    Science.gov (United States)

    Cao, Fu-Guang; Signal, A. I.

    We study flavour symmetry breaking in the nucleon's parton distribution functions (PDF) using the meson cloud model and `Pauli blocking' mechanism. It was found that the `Pauli blocking' contribution to the integrated polarized asymmetry is much larger than the meson cloud, in contrast to approximate equality in the unpolarized case. We also investigate charge symmetry breaking in the nucleon's PDF using the meson cloud model. Our results are very different from the quark model calculations.

  15. Evidence for SU(3) symmetry breaking from hyperon production

    International Nuclear Information System (INIS)

    Yang Jianjun

    2002-01-01

    We examine the SU(3) symmetry breaking in hyperon semileptonic decays (HSD) by considering two typical sets of quark contributions to the spin content of the octet baryons: set 1 with SU(3) flavor symmetry and set 2 with SU(3) flavor symmetry breaking in the HSD. The quark distributions of the octet baryons are calculated with a successful statistical model. Using an approximate relation between the quark fragmentation functions and the quark distributions, we predict the polarizations of the octet baryons produced in e + e - annihilation and semi-inclusive deep lepton-nucleon scattering in order to reveal the SU(3) symmetry breaking effect on the spin structure of the octet baryons. We find that the SU(3) symmetry breaking significantly affects the hyperon polarization. The available experimental data on the Λ polarization seem to favor the theoretical predictions with SU(3) symmetry breaking. We conclude that there is a possibility to get collateral evidence for SU(3) symmetry breaking from hyperon production. The theoretical errors for our predictions are discussed

  16. Classification of a Supersolid: Trial Wavefunctions, Symmetry Breakings and Excitation Spectra

    Science.gov (United States)

    Chen, Yu; Ye, Jinwu; Tian, Guangshan

    2012-11-01

    A state of matter is characterized by its symmetry breaking and elementary excitations. A supersolid is a state which breaks both translational symmetry and internal U(1) symmetry. Here, we review some past and recent works in phenomenological Ginsburg-Landau theories, ground state trial wavefunctions and microscopic numerical calculations. We also write down a new effective supersolid Hamiltonian on a lattice. The eigenstates of the Hamiltonian contains both the ground state wavefunction and all the excited states (supersolidon) wavefunctions. We contrast various kinds of supersolids in both continuous systems and on lattices, both condensed matter and cold atom systems. We provide additional new insights in studying their order parameters, symmetry breaking patterns, the excitation spectra and detection methods.

  17. Effects of symmetry breaking in finite quantum systems

    Energy Technology Data Exchange (ETDEWEB)

    Birman, J.L. [Department of Physics, City College, City University of New York, New York, NY 10031 (United States); Nazmitdinov, R.G. [Departament de Fisica, Universitat de les Illes Balears, Palma de Mallorca 07122 (Spain); Bogolubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation); Yukalov, V.I., E-mail: yukalov@theor.jinr.ru [Bogolubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation)

    2013-05-15

    The review considers the peculiarities of symmetry breaking and symmetry transformations and the related physical effects in finite quantum systems. Some types of symmetry in finite systems can be broken only asymptotically. However, with a sufficiently large number of particles, crossover transitions become sharp, so that symmetry breaking happens similarly to that in macroscopic systems. This concerns, in particular, global gauge symmetry breaking, related to Bose–Einstein condensation and superconductivity, or isotropy breaking, related to the generation of quantum vortices, and the stratification in multicomponent mixtures. A special type of symmetry transformation, characteristic only for finite systems, is the change of shape symmetry. These phenomena are illustrated by the examples of several typical mesoscopic systems, such as trapped atoms, quantum dots, atomic nuclei, and metallic grains. The specific features of the review are: (i) the emphasis on the peculiarities of the symmetry breaking in finite mesoscopic systems; (ii) the analysis of common properties of physically different finite quantum systems; (iii) the manifestations of symmetry breaking in the spectra of collective excitations in finite quantum systems. The analysis of these features allows for the better understanding of the intimate relation between the type of symmetry and other physical properties of quantum systems. This also makes it possible to predict new effects by employing the analogies between finite quantum systems of different physical nature.

  18. D7 brane embeddings and chiral symmetry breaking

    International Nuclear Information System (INIS)

    Evans, Nick; Waterson, Tom; Shock, Jonathan P.

    2005-01-01

    We study the embedding of D7 brane probes in five geometries that are deformations of AdS 5 xS 5 . Each case corresponds to the inclusion of quark fields in a dual gauge theory where we are interested in investigating whether chiral symmetry breaking occurs. We use a supersymmetric geometry describing an N=2 theory on its moduli space and a dilaton driven non-supersymmetric flow to establish criteria for a chiral symmetry breaking embedding. We develop a simple spherical D7 embedding that tests the repulsion of the core of the geometry and signals dynamical symmetry breaking. We then use this tool in more complicated geometries to show that an N=2* theory and a non-supersymmetric theory with scalar masses do not induce a chiral condensate. Finally we provide evidence that the Yang Mills* geometry does. (author)

  19. Introduction to symmetry-breaking phenomena in physics

    CERN Multimedia

    CERN. Geneva. Audiovisual Unit

    2001-01-01

    The notion of broken symmetries started slowly to emerge in the 19th century. The early studies of Pasteur on the parity asymmetry of life, the studies of Curie on piezoelectricity and on the symmetries of effects versus the symmetry of causes ( which clearly excluded spontaneous symmetry breaking), are important historical landmarks. However the possibility of spontaneous symmetry breaking within the usual principles of statistical mechanics, waited for the work of Peierls and Onsager. The whole theory of phase transitions and critical phenomena, as well as the construction of field theoretic models as long distance limit of yet unknown physics, relies nowadays on the concept of criticality associated to spontaneous symmetry breaking. The phenomena of Goldstone bosons, of Meissner-Higgs effects, are central to the theory of condensed matter as well as to particle physics. In cosmology as well, the various inflationary scenarios begin similarly with this same concept. The three lectures will provide a simple ...

  20. Cobimaximal lepton mixing from soft symmetry breaking

    Science.gov (United States)

    Grimus, W.; Lavoura, L.

    2017-11-01

    Cobimaximal lepton mixing, i.e.θ23 = 45 ° and δ = ± 90 ° in the lepton mixing matrix V, arises as a consequence of SV =V* P, where S is the permutation matrix that interchanges the second and third rows of V and P is a diagonal matrix of phase factors. We prove that any such V may be written in the form V = URP, where U is any predefined unitary matrix satisfying SU =U*, R is an orthogonal, i.e. real, matrix, and P is a diagonal matrix satisfying P2 = P. Using this theorem, we demonstrate the equivalence of two ways of constructing models for cobimaximal mixing-one way that uses a standard CP symmetry and a different way that uses a CP symmetry including μ-τ interchange. We also present two simple seesaw models to illustrate this equivalence; those models have, in addition to the CP symmetry, flavour symmetries broken softly by the Majorana mass terms of the right-handed neutrino singlets. Since each of the two models needs four scalar doublets, we investigate how to accommodate the Standard Model Higgs particle in them.

  1. Localization and Symmetry Breaking in the Quantum Quasiperiodic Ising Glass

    Directory of Open Access Journals (Sweden)

    A. Chandran

    2017-09-01

    Full Text Available Quasiperiodic modulation can prevent isolated quantum systems from equilibrating by localizing their degrees of freedom. In this article, we show that such systems can exhibit dynamically stable long-range orders forbidden in equilibrium. Specifically, we show that the interplay of symmetry breaking and localization in the quasiperiodic quantum Ising chain produces a quasiperiodic Ising glass stable at all energy densities. The glass order parameter vanishes with an essential singularity at the melting transition with no signatures in the equilibrium properties. The zero-temperature phase diagram is also surprisingly rich, consisting of paramagnetic, ferromagnetic, and quasiperiodically alternating ground-state phases with extended, localized, and critically delocalized low-energy excitations. The system exhibits an unusual quantum Ising transition whose properties are intermediate between those of the clean and infinite randomness Ising transitions. Many of these results follow from a geometric generalization of the Aubry-André duality that we develop. The quasiperiodic Ising glass may be realized in near-term quantum optical experiments.

  2. Chiral symmetry breaking and the pion quark structure

    International Nuclear Information System (INIS)

    Bernard, V.

    1986-01-01

    The mechanism of dynamical breaking of chiral symmetry in hadronic matter is first studied in the framework of the Nambu and Jona-Lasinio model on one hand and its generalisation to finite hadron size on the other hand. The analysis uses a variational procedure modelled after the BCS superconductor. Our study indicates for example, a great sensitivity of various quantities characterizing the breaking of symmetry to the shape of the interaction. Also the mechanism of breaking of chiral symmetry is essentially related to the mechanism of confinement. When a symmetry is spontaneously broken, there exists a Goldstone particle of zero mass. This is true in our model. This particle, the pion, is obtained as solution of a Bethe Salpeter equation for a qantiq bound state. This enables us to establish a connection between the pion as a Goldstone boson related to spontaneous symmetry breaking and the quark-antiquark structure of the pion. The finite mass of the physical pion is obtained with non zero current quark mass. Various properties of this particle are then studied in the RPA formalism. One important point of our model is the highly collective character of the pion. 85 refs [fr

  3. Finding strongly interacting symmetry breaking at the SSC

    International Nuclear Information System (INIS)

    Golden, M.

    1989-02-01

    Pairs of gauge bosons, W and Z, are a probe of the electroweak symmetry-breaking sector, since the numbers of two gauge boson events are much larger in strongly coupled models than weak. The doubly charged channels W + W + and W/sup /minus//W/sup/minus// are cleanest, since they do not suffer from q/bar q/ or gg fusion backgrounds. The like-charged gauge boson events are observable only if the symmetry breaking sector is strongly interacting. 19 refs., 4 figs., 2 tabs

  4. Chiral symmetry breaking in a semilocalized magnetic field

    Science.gov (United States)

    Cao, Gaoqing

    2018-03-01

    In this work, we explore the pattern of chiral symmetry breaking and restoration in a solvable magnetic field configuration within the Nambu-Jona-Lasinio model. The special semilocalized static magnetic field can roughly mimic the realistic situation in peripheral heavy ion collisions; thus, the study is important for the dynamical evolution of quark matter. We find that the magnetic-field-dependent contribution from discrete spectra usually dominates over the contribution from continuum spectra and chiral symmetry breaking is locally catalyzed by both the magnitude and scale of the magnetic field. The study is finally extended to the case with finite temperature or chemical potential.

  5. Effective field theory of emergent symmetry breaking in deformed atomic nuclei

    International Nuclear Information System (INIS)

    Papenbrock, T; Weidenmüller, H A

    2015-01-01

    Spontaneous symmetry breaking in non-relativistic quantum systems has previously been addressed in the framework of effective field theory. Low-lying excitations are constructed from Nambu–Goldstone modes using symmetry arguments only. We extend that approach to finite systems. The approach is very general. To be specific, however, we consider atomic nuclei with intrinsically deformed ground states. The emergent symmetry breaking in such systems requires the introduction of additional degrees of freedom on top of the Nambu–Goldstone modes. Symmetry arguments suffice to construct the low-lying states of the system. In deformed nuclei these are vibrational modes each of which serves as band head of a rotational band. (paper)

  6. Symmetry Breaking in Photonic Crystals: On-Demand Dispersion from Flatband to Dirac Cones.

    Science.gov (United States)

    Nguyen, H S; Dubois, F; Deschamps, T; Cueff, S; Pardon, A; Leclercq, J-L; Seassal, C; Letartre, X; Viktorovitch, P

    2018-02-09

    We demonstrate that symmetry breaking opens a new degree of freedom to tailor energy-momentum dispersion in photonic crystals. Using a general theoretical framework in two illustrative practical structures, we show that breaking symmetry enables an on-demand tuning of the local density of states of the same photonic band from zero (Dirac cone dispersion) to infinity (flatband dispersion), as well as any constant density over an adjustable spectral range. As a proof of concept, we demonstrate experimentally the transformation of the very same photonic band from a conventional quadratic shape to a Dirac dispersion, a flatband dispersion, and a multivalley one. This transition is achieved by finely tuning the vertical symmetry breaking of the photonic structures. Our results provide an unprecedented degree of freedom for optical dispersion engineering in planar integrated photonic devices.

  7. Symmetry Breaking in Photonic Crystals: On-Demand Dispersion from Flatband to Dirac Cones

    Science.gov (United States)

    Nguyen, H. S.; Dubois, F.; Deschamps, T.; Cueff, S.; Pardon, A.; Leclercq, J.-L.; Seassal, C.; Letartre, X.; Viktorovitch, P.

    2018-02-01

    We demonstrate that symmetry breaking opens a new degree of freedom to tailor energy-momentum dispersion in photonic crystals. Using a general theoretical framework in two illustrative practical structures, we show that breaking symmetry enables an on-demand tuning of the local density of states of the same photonic band from zero (Dirac cone dispersion) to infinity (flatband dispersion), as well as any constant density over an adjustable spectral range. As a proof of concept, we demonstrate experimentally the transformation of the very same photonic band from a conventional quadratic shape to a Dirac dispersion, a flatband dispersion, and a multivalley one. This transition is achieved by finely tuning the vertical symmetry breaking of the photonic structures. Our results provide an unprecedented degree of freedom for optical dispersion engineering in planar integrated photonic devices.

  8. Partial Symmetry Breaking by Local Search in the Group

    NARCIS (Netherlands)

    Prestwich, S.; Hnich, B.; Simonis, H.; Rossi, R.; Tarim, S.A.

    2012-01-01

    The presence of symmetry in constraint satisfaction problems can cause a great deal of wasted search effort, and several methods for breaking symmetries have been reported. In this paper we describe a new method called Symmetry Breaking by Nonstationary Optimisation, which interleaves local search

  9. Minimally doubled fermions and spontaneous chiral symmetry breaking

    Directory of Open Access Journals (Sweden)

    Osmanaj (Zeqirllari Rudina

    2018-01-01

    Full Text Available Chiral symmetry breaking in massless QCD is a very important feature in the current understanding of low energy physics. Low - lying Dirac modes are suitable to help us understand the spontaneous chiral symmetry breaking, since the formation of a non zero chiral condensate is an effect of their accumulation near zero. The Banks – Casher relation links the spectral density of the Dirac operator to the condensate with an identity that can be read in both directions. In this work we propose a spectral method to achieve a reliable determination of the density of eigenvalues of Dirac operator near zero using the Gauss – Lanczos quadrature. In order to understand better the dynamical chiral symmetry breaking and use the method we propose, we have chosen to work with minimally doubled fermions. These kind of fermions have been proposed as a strictly local discretization of the QCD fermions action, which preserves chiral symmetry at finite cut-off. Being chiral fermions, is easier to work with them and their low - lying Dirac modes and to understand the dynamical spontaneous chiral symmetry breaking.

  10. The origin of a primordial genome through spontaneous symmetry breaking

    NARCIS (Netherlands)

    Takeuchi, Nobuto|info:eu-repo/dai/nl/304836966; Hogeweg, P|info:eu-repo/dai/nl/073710725; Kaneko, Kunihiko

    2017-01-01

    The heredity of a cell is provided by a small number of non-catalytic templates-The genome. How did genomes originate? Here, we demonstrate the possibility that genome-like molecules arise from symmetry breaking between complementary strands of self-replicating molecules. Our model assumes a

  11. Electroweak Symmetry Breaking without Higgs Bosons at LHC

    CERN Document Server

    Delsart, P A

    2007-01-01

    It is possible that Electroweak Symmetry Breaking does not occur in Nature through the Higgs mechanism. Several alternate scenarios are studied at LHC experiment and this presentation review some of them : Technicolor searches in CMS and and Vector Boson Scattering in the Chiral Lagrangian model or in extra-dimension model in Atlas.

  12. Simple mathematical models of symmetry breaking. Application to particle physics

    International Nuclear Information System (INIS)

    Michel, L.

    1976-01-01

    Some mathematical facts relevant to symmetry breaking are presented. A first mathematical model deals with the smooth action of compact Lie groups on real manifolds, a second model considers linear action of any group on real or complex finite dimensional vector spaces. Application of the mathematical models to particle physics is considered. (B.R.H.)

  13. Minimally doubled fermions and spontaneous chiral symmetry breaking

    Science.gov (United States)

    Osmanaj (Zeqirllari), Rudina; Hyka (Xhako), Dafina

    2018-03-01

    Chiral symmetry breaking in massless QCD is a very important feature in the current understanding of low energy physics. Low - lying Dirac modes are suitable to help us understand the spontaneous chiral symmetry breaking, since the formation of a non zero chiral condensate is an effect of their accumulation near zero. The Banks - Casher relation links the spectral density of the Dirac operator to the condensate with an identity that can be read in both directions. In this work we propose a spectral method to achieve a reliable determination of the density of eigenvalues of Dirac operator near zero using the Gauss - Lanczos quadrature. In order to understand better the dynamical chiral symmetry breaking and use the method we propose, we have chosen to work with minimally doubled fermions. These kind of fermions have been proposed as a strictly local discretization of the QCD fermions action, which preserves chiral symmetry at finite cut-off. Being chiral fermions, is easier to work with them and their low - lying Dirac modes and to understand the dynamical spontaneous chiral symmetry breaking.

  14. Radiative symmetry breaking from interacting UV fixed points

    DEFF Research Database (Denmark)

    Abel, Steven; Sannino, Francesco

    2017-01-01

    It is shown that the addition of positive mass-squared terms to asymptotically safe gauge-Yukawa theories with perturbative UV fixed points leads to calculable radiative symmetry breaking in the IR. This phenomenon, and the multiplicative running of the operators that lies behind it, is akin...

  15. Enantioselective Symmetry Breaking Directed by the Order of Process Steps

    NARCIS (Netherlands)

    Noorduin, Wim L.; Meekes, Hugo; Enckevort, Willem J.P. van; Kaptein, Bernard; Kellogg, Richard M.; Vlieg, Elias

    2010-01-01

    Going forward in reverse: The configuration of the product of grinding-induced symmetry breaking can be controlled simply by the order in which the different reaction-mixture components are combined. The underlying mechanism is based on a subtle balance between enantioselective crystal growth and

  16. Optimal Spatial Harvesting Strategy and Symmetry-Breaking

    International Nuclear Information System (INIS)

    Kurata, Kazuhiro; Shi Junping

    2008-01-01

    A reaction-diffusion model with logistic growth and constant effort harvesting is considered. By minimizing an intrinsic biological energy function, we obtain an optimal spatial harvesting strategy which will benefit the population the most. The symmetry properties of the optimal strategy are also discussed, and related symmetry preserving and symmetry breaking phenomena are shown with several typical examples of habitats

  17. Model for dynamical chiral symmetry breaking and quark condensate

    International Nuclear Information System (INIS)

    Nekrasov, M.L.; Rochev, V.E.

    1986-01-01

    In the framework of the model, proposed earlier to describe nonperturbative QCD, the singularity of the type 1/k 4 in the gluon propagator is shown to result in dynamical chiral symmetry breaking and appearance of quark condensate. The value, obtained for quark condensate, is close to the phenomenological one

  18. Spontaneous symmetry breaking in spinor Bose-Einstein condensates

    DEFF Research Database (Denmark)

    Scherer, Manuel; Lücke, Bernd; Peise, Jan

    2013-01-01

    We present an analytical model for the theoretical analysis of spin dynamics and spontaneous symmetry breaking in a spinor Bose-Einstein condensate (BEC). This allows for an excellent intuitive understanding of the processes and provides good quantitative agreement with the experimental results...

  19. Strong electroweak symmetry breaking signals in WW scattering at TESLA

    CERN Document Server

    Chierici, R; Kobel, M

    2000-01-01

    A realistic study of the sensitivity to signals of strong electroweak symmetry breaking at TESLA energies using ee to WW nu nu and ee to ZZ nu nu processes is presented. Limits on alpha /sub 4/ and alpha /sub 5/, parameters of the electroweak chiral lagrangian, are given and discussed. (8 refs).

  20. Time-reversal symmetry breaking by ac field: Effect of ...

    Indian Academy of Sciences (India)

    Time-reversal symmetry breaking by ac field: Effect of commensurability in the frequency domain. V E KRAVTSOV. Present address: The Abdus Salam International Centre for Theoretical Physics, P.O. Box 586, 34100. Trieste, Italy. Landau Institute for Theoretical Physics, 2 Kosygina Street, 117940 Moscow, Russia.

  1. Charge symmetry breaking in the A=4 hypernuclei

    Czech Academy of Sciences Publication Activity Database

    Gazda, Daniel; Gal, A.

    2016-01-01

    Roč. 954, OCT (2016), s. 161-175 ISSN 0375-9474 R&D Projects: GA ČR(CZ) GA15-04301S Institutional support: RVO:61389005 Keywords : hypernuclei * hyperon-nucleon interactions * charge symmetry breaking Subject RIV: BE - Theoretical Physics Impact factor: 1.916, year: 2016

  2. Impact of local symmetry breaking on the physical properties of tetrahedral liquids.

    Science.gov (United States)

    Shi, Rui; Tanaka, Hajime

    2018-02-27

    Water and silica are the most important materials with local tetrahedral symmetry. They have similar crystalline polymorphs and exhibit anomalous density maximum in the liquid state. However, water and silica also show very different characteristics. For instance, the density of water varies much more sharply than that of liquid silica near the maximum as temperature changes. More notably, silica is a very good glass-former, but water is an extremely poor one. The physical origins of these similarities and differences still remain elusive, due to the lack of a microscopic understanding of the structural ordering in these two important liquids. Here, by accessing microscopic structural information by computer simulations, we reveal that local translational symmetry breaking is responsible for the density anomalies. On the other hand, the difference in the degree of local orientational symmetry breaking between water and silica, which originates from the difference in their bonding nature, causes not only the difference in the sharpness of density anomalies, but also their distinct glass-forming abilities. Our work not only shows the crucial roles of local translational and orientational symmetry breaking in the physical properties of the two extremely important materials, water and silica, but also provides a unified scenario applicable for other tetrahedral liquids such as Si, Ge, C, BeF 2 , and GeO 2 .

  3. Second order optical nonlinearity in silicon by symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Cazzanelli, Massimo, E-mail: massimo.cazzanelli@unitn.it [Laboratorio IdEA, Dipartimento di Fisica, Università di Trento, via Sommarive, 14 Povo (Trento) (Italy); Schilling, Joerg, E-mail: joerg.schilling@physik.uni-halle.de [Centre for Innovation Competence SiLi-nano, Martin-Luther-University Halle-Wittenberg, Karl-Freiherr-von-Fritsch Str. 3, 06120 Halle (Germany)

    2016-03-15

    Although silicon does not possess a dipolar bulk second order nonlinear susceptibility due to its centro-symmetric crystal structure, in recent years several attempts were undertaken to create such a property in silicon. This review presents the different sources of a second order susceptibility (χ{sup (2)}) in silicon and the connected second order nonlinear effects which were investigated up to now. After an introduction, a theoretical overview discusses the second order nonlinearity in general and distinguishes between the dipolar contribution—which is usually dominating in non-centrosymmetric structures—and the quadrupolar contribution, which even exists in centro-symmetric materials. Afterwards, the classic work on second harmonic generation from silicon surfaces in reflection measurements is reviewed. Due to the abrupt symmetry breaking at surfaces and interfaces locally a dipolar second order susceptibility appears, resulting in, e.g., second harmonic generation. Since the bulk contribution is usually small, the study of this second harmonic signal allows a sensitive observation of the surface/interface conditions. The impact of covering films, strain, electric fields, and defect states at the interfaces was already investigated in this way. With the advent of silicon photonics and the search for ever faster electrooptic modulators, the interest turned to the creation of a dipolar bulk χ{sup (2)} in silicon. These efforts have been focussing on several experiments applying an inhomogeneous strain to the silicon lattice to break its centro-symmetry. Recent results suggesting the impact of electric fields which are exerted from fixed charges in adjacent covering layers are also included. After a subsequent summary on “competing” concepts using not Si but Si-related materials, the paper will end with some final conclusions, suggesting possible future research direction in this dynamically developing field.

  4. Spontaneous Symmetry Breaking as a Basis of Particle Mass

    Energy Technology Data Exchange (ETDEWEB)

    Quigg, Chris; /Fermilab /CERN

    2007-04-01

    Electroweak theory joins electromagnetism with the weak force in a single quantum field theory, ascribing the two fundamental interactions--so different in their manifestations--to a common symmetry principle. How the electroweak gauge symmetry is hidden is one of the most urgent and challenging questions facing particle physics. The provisional answer incorporated in the ''standard model'' of particle physics was formulated in the 1960s by Higgs, by Brout & Englert, and by Guralnik, Hagen, & Kibble: The agent of electroweak symmetry breaking is an elementary scalar field whose self-interactions select a vacuum state in which the full electroweak symmetry is hidden, leaving a residual phase symmetry of electromagnetism. By analogy with the Meissner effect of the superconducting phase transition, the Higgs mechanism, as it is commonly known, confers masses on the weak force carriers W{sup {+-}} and Z. It also opens the door to masses for the quarks and leptons, and shapes the world around us. It is a good story--though an incomplete story--and we do not know how much of the story is true. Experiments that explore the Fermi scale (the energy regime around 1 TeV) during the next decade will put the electroweak theory to decisive test, and may uncover new elements needed to construct a more satisfying completion of the electroweak theory. The aim of this article is to set the stage by reporting what we know and what we need to know, and to set some ''Big Questions'' that will guide our explorations.

  5. Spontaneous spherical symmetry breaking in atomic confinement

    Science.gov (United States)

    Sveshnikov, Konstantin; Tolokonnikov, Andrey

    2017-07-01

    The effect of spontaneous breaking of initial SO(3) symmetry is shown to be possible for an H-like atom in the ground state, when it is confined in a spherical box under general boundary conditions of "not going out" through the box surface (i.e. third kind or Robin's ones), for a wide range of physically reasonable values of system parameters. The most novel and nontrivial result, which has not been reported previously, is that such an effect takes place not only for attractive, but also for repulsive interactions of atomic electrons with the cavity environment. Moreover, in the limit of a large box size R ≫ aB the regime of an atom, soaring over a plane with boundary condition of "not going out", is reproduced, rather than a spherically symmetric configuration, which would be expected on the basis of the initial SO(3) symmetry of the problem.

  6. Symmetry breaking and restoration in Lifshitz type theories

    International Nuclear Information System (INIS)

    Farakos, K.; Metaxas, D.

    2012-01-01

    We consider the one-loop effective potential at zero and finite temperature in scalar field theories with anisotropic space-time scaling. For z=2, there is a symmetry breaking term induced at one loop at zero temperature and we find symmetry restoration through a first-order phase transition at high temperature. For z=3, we considered at first the case with a positive mass term at tree level and found no symmetry breaking effects induced at one loop, and then we study the case with a negative mass term at tree level where we cannot conclude about symmetry restoration effects at high temperature because of the imaginary parts that appear in the effective potential for small values of the scalar field.

  7. Spontaneous Symmetry Breaking in 5D Conformally Invariant Gravity

    Directory of Open Access Journals (Sweden)

    Taeyoon Moon

    2016-01-01

    Full Text Available We explore the possibility of the spontaneous symmetry breaking in 5D conformally invariant gravity, whose action consists of a scalar field nonminimally coupled to the curvature with its potential. Performing dimensional reduction via ADM decomposition, we find that the model allows an exact solution giving rise to the 4D Minkowski vacuum. Exploiting the conformal invariance with Gaussian warp factor, we show that it also admits a solution which implements the spontaneous breaking of conformal symmetry. We investigate its stability by performing the tensor perturbation and find the resulting system is described by the conformal quantum mechanics. Possible applications to the spontaneous symmetry breaking of time-translational symmetry along the dynamical fifth direction and the brane-world scenario are discussed.

  8. Chiral symmetry breaking in superfluid 3He-A.

    Science.gov (United States)

    Ikegami, H; Tsutsumi, Y; Kono, K

    2013-07-05

    Spontaneous symmetry breaking is an important concept in many branches of physics. In helium-3 ((3)He), the breaking of symmetry leads to the orbital chirality in the superfluid phase known as (3)He-A. Chirality is a fundamental property of (3)He-A, but its direct detection has been challenging. We report direct detection of chirality by transport measurements of electrons trapped below a free surface of (3)He-A. In particular, we observed the so-called intrinsic Magnus force experienced by a moving electron; the direction of the force directly reflected the chirality. We further showed that, at the superfluid transition, the system selected either right- or left-handed chirality. The observation of such selection directly demonstrates chiral symmetry breaking.

  9. Probing electroweak symmetry breaking at multi-TeV colliders

    International Nuclear Information System (INIS)

    Chanowitz, M.S.

    1987-01-01

    Low energy theorems are derived for scattering of longitudinally polarized W and Z's, providing the basis for an estimate of the observable signal if electroweak symmetry breaking is due to new physics at the TeV scale. A pp collider with L, √s = 40 TeV, 10 33 cm. -2 s -1 is just sufficient to observe the signal while pp colliders with 40, 10 32 or 20, 10 33 are not. A collider that is sensitive to the TeV-scale signal provides valuable information about symmetry breaking whether the masses of the associated new particles are below, within, or above the 1-2 TeV region. 6 refs., 6 figs., 2 tabs

  10. Symmetry breaking in occupation number based slave-particle methods

    Science.gov (United States)

    Georgescu, Alexandru B.; Ismail-Beigi, Sohrab

    2017-10-01

    We describe a theoretical approach to finding spontaneously symmetry-broken electronic phases due to strong electronic interactions when using recently developed slave-particle (slave-boson) approaches based on occupation numbers. We describe why, to date, spontaneous symmetry breaking has proven difficult to achieve in such approaches. We then provide a total energy based approach for introducing auxiliary symmetry-breaking fields into the solution of the slave-particle problem that leads to lowered total energies for symmetry-broken phases. We point out that not all slave-particle approaches yield energy lowering: the slave-particle model being used must explicitly describe the degrees of freedom that break symmetry. Finally, our total energy approach permits us to greatly simplify the formalism used to achieve a self-consistent solution between spinon and slave modes while increasing the numerical stability and greatly speeding up the calculations.

  11. Gedanken Worlds without Higgs: QCD-Induced Electroweak Symmetry Breaking

    Energy Technology Data Exchange (ETDEWEB)

    Quigg, Chris; /Fermilab /Karlsruhe U., TTP; Shrock, Robert; /YITP, Stony Brook

    2009-01-01

    To illuminate how electroweak symmetry breaking shapes the physical world, we investigate toy models in which no Higgs fields or other constructs are introduced to induce spontaneous symmetry breaking. Two models incorporate the standard SU(3){sub c} {circle_times} SU(2){sub L} {circle_times} U(1){sub Y} gauge symmetry and fermion content similar to that of the standard model. The first class--like the standard electroweak theory--contains no bare mass terms, so the spontaneous breaking of chiral symmetry within quantum chromodynamics is the only source of electroweak symmetry breaking. The second class adds bare fermion masses sufficiently small that QCD remains the dominant source of electroweak symmetry breaking and the model can serve as a well-behaved low-energy effective field theory to energies somewhat above the hadronic scale. A third class of models is based on the left-right-symmetric SU(3){sub c} {circle_times} SU(2){sub L} {circle_times} SU(2){sub R} {circle_times} U(1)B?L gauge group. In a fourth class of models, built on SU(4){sub PS} {circle_times} SU(2){sub L} {circle_times} SU(2){sub R} gauge symmetry, lepton number is treated as a fourth color. Many interesting characteristics of the models stem from the fact that the effective strength of the weak interactions is much closer to that of the residual strong interactions than in the real world. The Higgs-free models not only provide informative contrasts to the real world, but also lead us to consider intriguing issues in the application of field theory to the real world.

  12. Chiral symmetry breaking in gauge theories from Reggeon diagram analysis

    International Nuclear Information System (INIS)

    White, A.R.

    1991-01-01

    It is argued that reggeon diagrams can be used to study dynamical properties of gauge theories containing a large number of massless fermions. SU(2) gauge theory is studied in detail and it is argued that there is a high energy solution which is analogous to the solution of the massless Schwinger model. A generalized winding-number condensate produces the massless pseudoscalar spectrum associated with chiral symmetry breaking and a ''trivial'' S-Matrix

  13. Nonlocal symmetry breaking in Kaluza-Klein theories.

    Science.gov (United States)

    Masiero, A; Serone, M; Scrucca, C A; Silvestrini, L

    2001-12-17

    Scherk-Schwarz gauge symmetry breaking of a D-dimensional field theory model compactified on a circle is analyzed. It is explicitly shown that forbidden couplings in the unbroken theory appear in the one-loop effective action only in a nonlocal way, implying that they are finite at all orders in perturbation theory. This result can be understood as a consequence of the local gauge symmetry, but it holds true also in the global limit.

  14. Canonical forms of tensor representations and spontaneous symmetry breaking

    International Nuclear Information System (INIS)

    Cummins, C.J.

    1986-01-01

    An algorithm for constructing canonical forms for any tensor representation of the classical compact Lie groups is given. This method is used to find a complete list of the symmetry breaking patterns produced by Higgs fields in the third-rank antisymmetric representations of U(n), SU(n) and SO(n) for n<=7. A simple canonical form is also given for kth-rank symmetric tensor representations. (author)

  15. Explicit symmetry breaking in electrodynamic systems and electromagnetic radiation

    CERN Document Server

    Sinha, Dhiraj

    2016-01-01

    This book is an introduction to the concept of symmetries in electromagnetism and explicit symmetry breaking. It begins with a brief background on the origin of the concept of symmetry and its meaning in fields such as architecture, mathematics and physics. Despite the extensive developments of symmetry in these fields, it has yet to be applied to the context of classical electromagnetism and related engineering applications. This book unravels the beauty and excitement of this area to scientists and engineers.

  16. Inflation and cosmic strings in models with dynamical symmetry breaking

    International Nuclear Information System (INIS)

    Matheson, A.M.; Brandenberger, R.H.

    1989-01-01

    We derive the effective action for the composite field which in dynamical symmetry breaking plays the role of the Higgs field. We show that this effective action does not give rise to inflation. It is, however, possible to obtain topological defects such as cosmic strings. There will be fermionic zero modes trapped on the strings, and the strings will therefore be superconducting in a generalized sense. (orig.)

  17. Ras activation and symmetry breaking during Dictyostelium chemotaxis.

    Science.gov (United States)

    Kortholt, Arjan; Keizer-Gunnink, Ineke; Kataria, Rama; Van Haastert, Peter J M

    2013-10-01

    Central to chemotaxis is the molecular mechanism by which a shallow spatial gradient of chemoattractant induces symmetry breaking of activated signaling molecules. Previously, we have used Dictyostelium mutants to investigate the minimal requirements for chemotaxis, and identified a basal signaling module providing activation of Ras and F-actin at the leading edge. Here, we show that Ras activation after application of a pipette releasing the chemoattractant cAMP has three phases, each depending on specific guanine-nucleotide-exchange factors (GEFs). Initially a transient activation of Ras occurs at the entire cell boundary, which is proportional to the local cAMP concentrations and therefore slightly stronger at the front than in the rear of the cell. This transient Ras activation is present in gα2 (gpbB)-null cells but not in gβ (gpbA)-null cells, suggesting that Gβγ mediates the initial activation of Ras. The second phase is symmetry breaking: Ras is activated only at the side of the cell closest to the pipette. Symmetry breaking absolutely requires Gα2 and Gβγ, but not the cytoskeleton or four cAMP-induced signaling pathways, those dependent on phosphatidylinositol (3,4,5)-triphosphate [PtdIns(3,4,5)P3], cGMP, TorC2 and PLA2. As cells move in the gradient, the crescent of activated Ras in the front half of the cell becomes confined to a small area at the utmost front of the cell. Confinement of Ras activation leads to cell polarization, and depends on cGMP formation, myosin and F-actin. The experiments show that activation, symmetry breaking and confinement of Ras during Dictyostelium chemotaxis uses different G-protein subunits and a multitude of Ras GEFs and GTPase-activating proteins (GAPs).

  18. Time reversal symmetry breaking effects in resonant nuclear reactions

    International Nuclear Information System (INIS)

    Feshbach, H.; Hussein, M.S.; Kerman, A.K.

    1995-01-01

    We incorporate time reversal symmetry breaking (TRSB) effects into the theory of compound nuclear reactions. We show that the only meaningful test of TRSB in the overlapping resonances regime is through the study of cross-section correlations. The effect is channel-dependent. In the isolated resonance regime, we employ K-matrix theory to show the impact of TRSB using the fact that when only one eigen-channel participates in populating and depopulating the compound resonance. (orig.)

  19. Delayed fluorescence from upper excited singlet states of aromatic ketones

    International Nuclear Information System (INIS)

    Nickel, B.; Roden, G.

    1980-01-01

    With liquid solutions of the aromatic ketones anthraquinone and xanthone, a P-type delayed fluorescence from upper excited singlet states, resulting from triplet-triplet annihilation, has been observed. Some peculiarities of the triplet-triplet annihilation of aromatic ketones are discussed. (orig.)

  20. EXECUTIVE SUMMARY OF THE SNOWMASS 2001 WORKING GROUP : ELECTROWEAK SYMMETRY BREAKING

    International Nuclear Information System (INIS)

    CARENA, M.; GERDES, D.W.; HABER, H.E.; TURCOT, A.S.; ZERWAS, P.M.

    2001-01-01

    In this summary report of the 2001 Snowmass Electroweak Symmetry Breaking Working Group, the main candidates for theories of electroweak symmetry breaking are surveyed, and the criteria for distinguishing among the different approaches are discussed. The potential for observing electroweak symmetry breaking phenomena at the upgraded Tevatron and the LHC is described. We emphasize the importance of a high-luminosity e + e - linear collider for precision measurements to clarify the underlying electroweak symmetry breaking dynamics. Finally, we note the possible roles of the μ + μ - collider and VLHC for further elucidating the physics of electroweak symmetry breaking

  1. Chains of benzenes with lithium-atom adsorption: Vibrations and spontaneous symmetry breaking

    Science.gov (United States)

    Ortiz, Yenni P.; Stegmann, Thomas; Klein, Douglas J.; Seligman, Thomas H.

    2017-09-01

    We study effects of different configurations of adsorbates on the vibrational modes as well as symmetries of polyacenes and poly-p-phenylenes focusing on lithium atom adsorption. We found that the spectra of the vibrational modes distinguish the different configurations. For more regular adsorption schemes the lowest states are bending and torsion modes of the skeleton, which are essentially followed by the adsorbate. On poly-p-phenylenes we found that lithium adsorption reduces and often eliminates the torsion between rings thus increasing symmetry. There is spontaneous symmetry breaking in poly-p-phenylenes due to double adsorption of lithium atoms on alternating rings.

  2. On radiative gauge symmetry breaking in the minimal supersymmetric model

    International Nuclear Information System (INIS)

    Gamberini, G.; Ridolfi, G.; Zwirner, F.

    1990-01-01

    We present a critical reappraisal of radiative gauge symmetry breaking in the minimal supersymmetric standard model. We show that a naive use of the renormalization group improved tree-level potential can lead to incorrect conclusions. We specify the conditions under which the above method gives reliable results, by performing a comparison with the results obtained from the full one-loop potential. We also point out how the stability constraint and the conditions for the absence of charge- and colour-breaking minima should be applied. Finally, we comment on the uncertainties affecting the model predictions for physical observables, in particular for the top quark mass. (orig.)

  3. Non-local symmetry breaking in Kaluza-Klein theories

    CERN Document Server

    Masiero, A; Serone, M; Silvestrini, L

    2001-01-01

    Scherk-Schwarz gauge symmetry breaking of a D-dimensional field theory model compactified on a circle is analyzed. It is explicitly shown that forbidden couplings in the unbroken theory appear in the one-loop effective action only in a non-local way, implying that they are finite at all orders in perturbation theory. This result can be understood as a consequence of the local gauge symmetry, but holds true also in the global limit. Similar results for Scherk-Schwarz supersymmetry breaking are expected to hold.

  4. Asymmetric transmission of a planar metamaterial induced by symmetry breaking

    Science.gov (United States)

    Bai, Yu; Chen, Yuyan; Zhang, Yongyuan; Wang, Yongkai; Aba, Tudahong; Li, Hui; Wang, Li; Zhang, Zhongyue

    2018-03-01

    Asymmetric transmission (AT) is widely used in polarization transformers and polarization-controlled devices. In this paper, a planar metamaterial nanostructure with connected gammadion-shaped nanostructure (CGN) is proposed to achieve AT effect for forward and backward propagations of circular polarized light. The CGN arrays can produce magnetic moment oscillation that is normal to the metamaterial plane, which is weakly coupled to free space and generates transmission valleys. The introduction of symmetry breaking exerts a strong influence on the AT effects, and these effects can be tuned by the structural parameters. Our planar metamaterials may have potential for application in the future design of polarization-controlling devices.

  5. Multidimensional universes, Kaluza-Klein, Einstein spaces and symmetry breaking

    International Nuclear Information System (INIS)

    Coquereaux, R.

    1983-12-01

    The aim of these lectures was to present a review of the ''multidimensional universes'' where the old Kaluza-Klein idea holds true. I give first a survey of the theory of fiber bundles. Then there is a discussion on invariant metrics on groups and homogeneous spaces. Then comes a very short section on basic Riemannian geometry. The important results about the structure (topology and metric) of these multidimensional universes is given, the physical ideas are also discussed. In section 6 we show how to obtain many homogeneous Einstein metrics on groups and homogeneous spaces and study how they can lead to ''spontaneous symmetry breaking''

  6. Cosmological constraints on spontaneous R-symmetry breaking models

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, Yuta; Kobayashi, Tatsuo [Kyoto Univ. (Japan). Dept. of Physics; Kamada, Kohei [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Ookouchi, Yutaka [Kyoto Univ. (Japan). Dept. of Physics; Kyoto Univ. (Japan). The Hakubi Center for Advanced Research and Dept. of Physics

    2012-11-15

    We study general constraints on spontaneous R-symmetry breaking models coming from the cosmological effects of the pseudo Nambu-Goldstone bosons, R-axions. They are substantially produced in the early Universe and may cause several cosmological problems. We focus on relatively long-lived R-axions and find that in a wide range of parameter space, models are severely constrained. In particular, R-axions with mass less than 1 MeV are generally ruled out for relatively high reheating temperature, T{sub R}>10 GeV.

  7. Strong evidence for spontaneous chiral symmetry breaking in (quenched) QCD

    International Nuclear Information System (INIS)

    Barbour, I.M.; Gibbs, P.; Schierholz, G.; Teper, M.; Gilchrist, J.P.; Schneider, H.

    1983-09-01

    We calculate the chiral condensate for all quark masses using Kogut-Susskind fermions in lattice-regularized quenched QCD. The large volume behaviour of at small quark masses demonstrates that the explicit U(1) chiral symmetry is spontaneously broken. We perform the calculation for β = 5.1 to 5.9 and find very good continuum renormalization group behaviour. We infer that the spontaneous breaking we observe belongs to continuum QCD. This constitutes the first unambiguous demonstration of spontaneous chiral symmetry breaking in continuum quenched QCD. (orig.)

  8. Macroscopic influence on the spontaneous symmetry breaking in quantum field

    International Nuclear Information System (INIS)

    Kirzhnitz, D.A.

    1977-01-01

    Major results of investigations concerning macroscopic influence (heating, compression, external field and current) on elementary particle systems with spontaneous symmetry breaking are briefly reviewed. The study of this problem has been stimulated by recent progress in the unified renormalizable theory of elementary particles. Typically it appears that at some values of external parameters a phase transition with symmetry restoration takes place. There exists a profound and far going analogy with phase transition in many-body physics especially with superconductivity phenomenon. Some applications to cosmology are also considered

  9. Schwinger Dyson equations: Dynamical chiral symmetry breaking and confinement

    International Nuclear Information System (INIS)

    Roberts, C.D.

    1992-01-01

    A representative but not exhaustive review of the Schwinger-Dyson equation (SDE) approach to the nonperturbative study of QCD is presented. The main focus is the SDE for the quark self energy but studies of the gluon propagator and quark-gluon vertex are also discussed insofar as they are important to the quark SDE. The scope of this article is the application of these equations to the study of dynamical chiral symmetry breaking, quark confinement and the phenomenology of the spectrum and dynamics of QCD

  10. Sakai-Sugimoto model, tachyon condensation and chiral symmetry breaking

    International Nuclear Information System (INIS)

    Dhar, Avinash; Nag, Partha

    2008-01-01

    We modify the Sakai-Sugimoto model of chiral symmetry breaking to take into account the open string tachyon which stretches between the flavour D8-branes and D8-bar-branes. There are several reasons of consistency for doing this: (i) Even if it might be reasonable to ignore the tachyon in the ultraviolet where the flavour branes and antibranes are well separated and the tachyon is small, it is likely to condense and acquire large values in the infrared where the branes meet. This takes the system far away from the perturbatively stable minimum of the Sakai-Sugimoto model; (ii) The bifundamental coupling of the tachyon to fermions of opposite chirality makes it a suitable candidate for the quark mass and chiral condensate parameters. We show that the modified Sakai-Sugimoto model with the tachyon present has a classical solution satisfying all the desired consistency properties. In this solution chiral symmetry breaking coincides with tachyon condensation. We identify the parameters corresponding to the quark mass and the chiral condensate and also briefly discuss the mesonic spectra

  11. Symmetry breaking and singularity structure in Bose-Einstein condensates

    Science.gov (United States)

    Commeford, K. A.; Garcia-March, M. A.; Ferrando, A.; Carr, Lincoln D.

    2012-08-01

    We determine the trajectories of vortex singularities that arise after a single vortex is broken by a discretely symmetric impulse in the context of Bose-Einstein condensates in a harmonic trap. The dynamics of these singularities are analyzed to determine the form of the imprinted motion. We find that the symmetry-breaking process introduces two effective forces: a repulsive harmonic force that causes the daughter trajectories to be ejected from the parent singularity and a Magnus force that introduces a torque about the axis of symmetry. For the analytical noninteracting case we find that the parent singularity is reconstructed from the daughter singularities after one period of the trapping frequency. The interactions between singularities in the weakly interacting system do not allow the parent vortex to be reconstructed. Analytic trajectories were compared to the actual minima of the wave function, showing less than 0.5% error for an impulse strength of v=0.00005. We show that these solutions are valid within the impulse regime for various impulse strengths using numerical integration of the Gross-Pitaevskii equation. We also show that the actual duration of the symmetry-breaking potential does not significantly change the dynamics of the system as long as the strength is below v=0.0005.

  12. Parity-time symmetry breaking in magnetic systems

    Science.gov (United States)

    Galda, Alexey; Vinokur, Valerii

    The understanding of out-of-equilibrium physics, especially dynamic instabilities and dynamic phase transitions, is one of the major challenges of contemporary science, spanning the broadest wealth of research areas that range from quantum optics to living organisms. Focusing on nonequilibrium dynamics of an open dissipative spin system, we introduce a non-Hermitian Hamiltonian approach, in which non-Hermiticity reflects dissipation and deviation from equilibrium. The imaginary part of the proposed spin Hamiltonian describes the effects of Gilbert damping and applied Slonczewski spin-transfer torque. In the classical limit, our approach reproduces Landau-Lifshitz-Gilbert-Slonczewski dynamics of a large macrospin. We reveal the spin-transfer torque-driven parity-time symmetry-breaking phase transition corresponding to a transition from precessional to exponentially damped spin dynamics. Micromagnetic simulations for nanoscale ferromagnetic disks demonstrate the predicted effect. Our findings can pave the way to a general quantitative description of out-of-equilibrium phase transitions driven by spontaneous parity-time symmetry breaking.

  13. Symmetry and symmetry breaking in cancer: a foundational approach to the cancer problem.

    Science.gov (United States)

    Frost, J James; Pienta, Kenneth J; Coffey, Donald S

    2018-02-20

    Symmetry and symmetry breaking concepts from physics and biology are applied to the problem of cancer. Three categories of symmetry breaking in cancer are examined: combinatorial, geometric, and functional. Within these categories, symmetry breaking is examined for relevant cancer features, including epithelial-mesenchymal transition (EMT); tumor heterogeneity; tensegrity; fractal geometric and information structure; functional interaction networks; and network stabilizability and attack tolerance. The new cancer symmetry concepts are relevant to homeostasis loss in cancer and to its origin, spread, treatment and resistance. Symmetry and symmetry breaking could provide a new way of thinking and a pathway to a solution of the cancer problem.

  14. Symmetry breaking and physical properties of the bosonic single-impurity Anderson model

    Science.gov (United States)

    Warnes, J. H.; Miranda, E.

    2012-10-01

    We show how exact diagonalization of small clusters can be used as a fast and reliable impurity solver by determining the phase diagram and physical properties of the bosonic single-impurity Anderson model. This is specially important for applications which require the solution of a large number of different single-impurity problems, such as the bosonic dynamical mean field theory of disordered systems. In particular, we investigate the connection between spontaneous global gauge symmetry breaking and the occurrence of Bose-Einstein condensation (BEC). We show how BEC is accurately signaled by the appearance of broken symmetry, even when a fairly modest number of states is retained. The occurrence of symmetry breaking can be detected both by adding a small conjugate field or, as in generic quantum critical points, by the divergence of the associated phase susceptibility. Our results show excellent agreement with the considerably more demanding numerical renormalization group (NRG) method. We also investigate the mean impurity occupancy and its fluctuations, identifying an asymmetry in their critical behavior across the quantum phase transitions between BEC and `Mott' phases.

  15. Spin amplification by controlled symmetry breaking for spin-based logic

    Science.gov (United States)

    Kawakami, Roland K.

    2015-09-01

    Spin amplification is one of the most critical challenges for spintronics and spin-based logic in order to achieve spintronic circuits with fan-out. We propose a new concept for spin amplification that will allow a small spin current in a non-magnetic spin channel to control the magnetization of an attached ferromagnet. The key step is to bring the ferromagnet into an unstable symmetric state (USS), so that a small spin transfer torque from a small spin current can provide a magnetic bias to control the spontaneous symmetry breaking and select the final magnetization direction of the ferromagnet. Two proposed methods for achieving the USS configuration are voltage-controlled Curie temperature (VC-TC) and voltage-controlled magnetic anisotropy (VC-MA). We believe the development of new 2D magnetic materials with greater tunability of VC-TC and VC-MA will be needed for practical applications. A successful realization of spin amplification by controlled symmetry breaking will be important for the implementation of existing spin-logic proposals (e.g. ‘all spin logic’) and could inspire alternative ideas for spintronic circuits and devices.

  16. Spin amplification by controlled symmetry breaking for spin-based logic

    International Nuclear Information System (INIS)

    Kawakami, Roland K

    2015-01-01

    Spin amplification is one of the most critical challenges for spintronics and spin-based logic in order to achieve spintronic circuits with fan-out. We propose a new concept for spin amplification that will allow a small spin current in a non-magnetic spin channel to control the magnetization of an attached ferromagnet. The key step is to bring the ferromagnet into an unstable symmetric state (USS), so that a small spin transfer torque from a small spin current can provide a magnetic bias to control the spontaneous symmetry breaking and select the final magnetization direction of the ferromagnet. Two proposed methods for achieving the USS configuration are voltage-controlled Curie temperature (VC-T C ) and voltage-controlled magnetic anisotropy (VC-MA). We believe the development of new 2D magnetic materials with greater tunability of VC-T C and VC-MA will be needed for practical applications. A successful realization of spin amplification by controlled symmetry breaking will be important for the implementation of existing spin-logic proposals (e.g. ‘all spin logic’) and could inspire alternative ideas for spintronic circuits and devices. (paper)

  17. Jumps, somersaults, and symmetry breaking in Leidenfrost drops

    Science.gov (United States)

    Chen, Simeng; Bertola, Volfango

    2016-08-01

    When a droplet of water impacts a heated surface, the drop may be observed to bounce. Recently is has been found that small quantities (˜100 ppm) of polymer additives such as polyethylene oxide can significantly increase the maximum bouncing height of drops. This effect has been explained in terms of the reduction of energy dissipation caused by polymer additives during the drop retraction and rebound, resulting in higher mechanical energy available for bouncing. Here we demonstrate, by comparing three types of fluids (Newtonian, shear-thinning, and viscoelastic), that the total kinetic energy carried by low-viscosity Newtonian drops during retraction is partly transformed into rotational kinetic energy rather than dissipated when compared with high-viscosity or non-Newtonian drops. We also show that non-Newtonian effects play little role in the energy distribution during drop impact, while the main effect is due to the symmetry break observed during the retraction of low-viscosity drops.

  18. Vector models with spontaneous Lorentz-symmetry breaking

    Science.gov (United States)

    Escobar, C. A.; Urrutia, L. F.

    2018-01-01

    Even though models with spontaneous Lorentz-symmetry breaking also damage gauge invariance, an interesting possibility that emerges is to interpret the resultant massless Goldstone bosons as the gauge bosons of the related gauge theory. In this contribution we review the conditions under which gauge invariance is recovered from such models. To illustrate our general approach we consider the classical Abelian bumblebee and Nambu models. In the former case we prove its connection with electrodynamics by a procedure which takes proper care of the gauge-fixing conditions. In the case of the Abelian Nambu model its relation with electrodynamics is established in such a way that the generalization to the non-Abelian case is straightforward.

  19. Confinement and dynamical chiral symmetry breaking in QED3

    International Nuclear Information System (INIS)

    Bashir, A.; Raya, A.; Cloeet, I. C.; Roberts, C. D.

    2008-01-01

    We establish that QED3 can possess a critical number of flavors, N f c , associated with dynamical chiral symmetry breaking if, and only if, the fermion wave function renormalization and photon vacuum polarization are homogeneous functions at infrared momenta when the fermion mass function vanishes. The Ward identity entails that the fermion-photon vertex possesses the same property and ensures a simple relationship between the homogeneity degrees of each of these functions. Simple models for the photon vacuum polarization and fermion-photon vertex are used to illustrate these observations. The existence and value of N f c are contingent upon the precise form of the vertex but any discussion of gauge dependence is moot. We introduce an order parameter for confinement. Chiral symmetry restoration and deconfinement are coincident owing to an abrupt change in the analytic properties of the fermion propagator when a nonzero scalar self-energy becomes insupportable

  20. e +e- modes and U(1) spontaneous chiral symmetry breaking

    International Nuclear Information System (INIS)

    Steininger, K.

    1992-01-01

    In this paper, motivated by evidence for a chiral phase transition in strong coupling lattice QED, the authors calculate the two-particle spectrum of the broken QED phase. This is done in the framework of a Nambu and Jona-Lasinio model with U(1) symmetry including chiral symmetry and symmetry breaking properties of QED. The second order chiral phase transition behavior in our model and in lattice QED are in excellent agreement. The authors then present a detailed analysis of the spectra of the e + e - modes in the broken phase. The authors examine whether these modes have any possible relationship to the narrow e + e - resonances found in soft heavy ion collisions at GSL. The authors' answer is negative

  1. Inertial Spontaneous Symmetry Breaking and Quantum Scale Invariance

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Pedro G. [Oxford U.; Hill, Christopher T. [Fermilab; Ross, Graham G. [Oxford U., Theor. Phys.

    2018-01-23

    Weyl invariant theories of scalars and gravity can generate all mass scales spontaneously, initiated by a dynamical process of "inertial spontaneous symmetry breaking" that does not involve a potential. This is dictated by the structure of the Weyl current, $K_\\mu$, and a cosmological phase during which the universe expands and the Einstein-Hilbert effective action is formed. Maintaining exact Weyl invariance in the renormalised quantum theory is straightforward when renormalisation conditions are referred back to the VEV's of fields in the action of the theory, which implies a conserved Weyl current. We do not require scale invariant regulators. We illustrate the computation of a Weyl invariant Coleman-Weinberg potential.

  2. Stock market speculation: Spontaneous symmetry breaking of economic valuation

    Science.gov (United States)

    Sornette, Didier

    2000-09-01

    Firm foundation theory estimates a security's firm fundamental value based on four determinants: expected growth rate, expected dividend payout, the market interest rate and the degree of risk. In contrast, other views of decision-making in the stock market, using alternatives such as human psychology and behavior, bounded rationality, agent-based modeling and evolutionary game theory, expound that speculative and crowd behavior of investors may play a major role in shaping market prices. Here, we propose that the two views refer to two classes of companies connected through a "phase transition". Our theory is based on (1) the identification of the fundamental parity symmetry of prices (p→-p), which results from the relative direction of payment flux compared to commodity flux and (2) the observation that a company's risk-adjusted growth rate discounted by the market interest rate behaves as a control parameter for the observable price. We find a critical value of this control parameter at which a spontaneous symmetry-breaking of prices occurs, leading to a spontaneous valuation in absence of earnings, similarly to the emergence of a spontaneous magnetization in Ising models in absence of a magnetic field. The low growth rate phase is described by the firm foundation theory while the large growth rate phase is the regime of speculation and crowd behavior. In practice, while large "finite-time horizon" effects round off the predicted singularities, our symmetry-breaking speculation theory accounts for the apparent over-pricing and the high volatility of fast growing companies on the stock markets.

  3. Spontaneous symmetry breaking and neutral stability in the noncanonical Hamiltonian formalism

    International Nuclear Information System (INIS)

    Morrison, P.J.; Eliezer, S.

    1985-10-01

    The noncanonical Hamiltonian formalism is based upon a generalization of the Poisson bracket, a particular form of which is possessed by continuous media fields. Associated with this generalization are special constants of motion called Casimirs. These are constants that can be viewed as being built into the phase space, for they are invariant for all Hamiltonians. Casimirs are important because when added to the Hamiltonian they yield an effective Hamiltonian that produces equilibrium states upon variation. The stability of these states can be ascertained by a second variation. Goldstone's theorem, in its usual context, determines zero eigenvalues of the mass matrix for a given vacuum state, the equilibrium with minimum energy. Here, since for fluids and plasmas the vacuum state is uninteresting, we examine symmetry breaking for general equilibria. Broken symmetries imply directions of neutral stability. Two examples are presented: the nonlinear Alfven wave of plasma physics and the Korteweg-de Vries soliton. 46 refs

  4. Symmetry breaking on density in escaping ants: experiment and alarm pheromone model.

    Directory of Open Access Journals (Sweden)

    Geng Li

    Full Text Available The symmetry breaking observed in nature is fascinating. This symmetry breaking is observed in both human crowds and ant colonies. In such cases, when escaping from a closed space with two symmetrically located exits, one exit is used more often than the other. Group size and density have been reported as having no significant impact on symmetry breaking, and the alignment rule has been used to model symmetry breaking. Density usually plays important roles in collective behavior. However, density is not well-studied in symmetry breaking, which forms the major basis of this paper. The experiment described in this paper on an ant colony displays an increase then decrease of symmetry breaking versus ant density. This result suggests that a Vicsek-like model with an alignment rule may not be the correct model for escaping ants. Based on biological facts that ants use pheromones to communicate, rather than seeing how other individuals move, we propose a simple yet effective alarm pheromone model. The model results agree well with the experimental outcomes. As a measure, this paper redefines symmetry breaking as the collective asymmetry by deducing the random fluctuations. This research indicates that ants deposit and respond to the alarm pheromone, and the accumulation of this biased information sharing leads to symmetry breaking, which suggests true fundamental rules of collective escape behavior in ants.

  5. WHY COLOR-FLAVOR LOCKING IS JUST LIKE CHIRAL SYMMETRY BREAKING

    International Nuclear Information System (INIS)

    PISARSKI, R.D.; RISCHKE, D.H.

    2000-01-01

    The authors review how a classification into representations of color and flavor can be used to understand the possible patterns of symmetry breaking for color superconductivity in dense quark matter. In particular, the authors show how for three flavors, color-flavor locking is precisely analogous to the usual pattern of chiral symmetry breaking in the QCD vacuum

  6. arXiv Radiative symmetry breaking from interacting UV fixed points

    CERN Document Server

    Abel, Steven

    2017-09-28

    It is shown that the addition of positive mass-squared terms to asymptotically safe gauge-Yukawa theories with perturbative UV fixed points leads to calculable radiative symmetry breaking in the IR. This phenomenon, and the multiplicative running of the operators that lies behind it, is akin to the radiative symmetry breaking that occurs in the supersymmetric standard model.

  7. Time-reversal-symmetry breaking in circuit-QED-based photon lattices

    Science.gov (United States)

    Koch, Jens; Houck, Andrew A.; Hur, Karyn Le; Girvin, S. M.

    2010-10-01

    Breaking time-reversal symmetry is a prerequisite for accessing certain interesting many-body states such as fractional quantum Hall states. For polaritons, charge neutrality prevents magnetic fields from providing a direct symmetry-breaking mechanism and, similar to the situation in ultracold atomic gases, an effective magnetic field has to be synthesized. We show that in the circuit-QED architecture, this can be achieved by inserting simple superconducting circuits into the resonator junctions. In the presence of such coupling elements, constant parallel magnetic and electric fields suffice to break time-reversal symmetry. We support these theoretical predictions with numerical simulations for realistic sample parameters, specify general conditions under which time reversal is broken, and discuss the application to chiral Fock-state transfer, an on-chip circulator, and tunable band structure for the Kagome lattice.

  8. Probing the two-scale-factor universality hypothesis by exact rotation symmetry-breaking mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Neto, J.F.S.; Lima, K.A.L.; Carvalho, P.R.S. [Universidade Federal do Piaui, Departamento de Fisica, Teresina, PI (Brazil); Sena-Junior, M.I. [Universidade de Pernambuco, Escola Politecnica de Pernambuco, Recife, PE (Brazil); Universidade Federal de Alagoas, Instituto de Fisica, Maceio, AL (Brazil)

    2017-12-15

    We probe the two-scale-factor universality hypothesis by evaluating, firstly explicitly and analytically at the one-loop order, the loop quantum corrections to the amplitude ratios for O(N)λφ{sup 4} scalar field theories with rotation symmetry breaking in three distinct and independent methods in which the rotation symmetry-breaking mechanism is treated exactly. We show that the rotation symmetry-breaking amplitude ratios turn out to be identical in the three methods and equal to their respective rotation symmetry-breaking ones, although the amplitudes themselves, in general, depend on the method employed and on the rotation symmetry-breaking parameter. At the end, we show that all these results can be generalized, through an inductive process based on a general theorem emerging from the exact calculation, to any loop level and physically interpreted based on symmetry ideas. (orig.)

  9. Generation of macroscopic singlet states in atomic ensembles

    Science.gov (United States)

    Tóth, Géza; Mitchell, Morgan W.

    2010-05-01

    We study squeezing of the spin uncertainties by quantum non-demolition (QND) measurement in non-polarized spin ensembles. Unlike the case of polarized ensembles, the QND measurements can be performed with negligible back-action, which allows, in principle, perfect spin squeezing as quantified by Tóth et al (2007 Phys. Rev. Lett. 99 250405). The generated spin states approach many-body singlet states and contain a macroscopic number of entangled particles even when individual spin is large. We introduce the Gaussian treatment of unpolarized spin states and use it to estimate the achievable spin squeezing for realistic experimental parameters. Our proposal might have applications for magnetometry with a high spatial resolution or quantum memories storing information in decoherence free subspaces.

  10. Esoteric elementary particle phenomena in undergraduate physics: spontaneous symmetry breaking and scale invariance

    International Nuclear Information System (INIS)

    Greenberger, D.M.

    1978-01-01

    We take two rather abstract concepts from elementary particle physics, and show that there actually exist analogs to both of them in undergraduate physics. In the case of spontaneous symmetry breaking, we provide an example where the most symmetrical state of a simple system suddenly becomes unstable, while a less symmetrical state develops lower energy and becomes stable. In the case of scale invariance, we consider an example with no natural scale determined, and show that a straightforward dimensional analysis of the problem leads to incorrect results, because of the occurrence of infinities, even though they would appear to be irrelevant infinities that might not be expected to affect the dimensions of the answer. We then show how a simple use of the scale invariance of the problem leads to the correct answer

  11. Time-reversal symmetry breaking in the noncentrosymmetric superconductor Re6Ti

    Science.gov (United States)

    Singh, D.; K. P., Sajilesh; Barker, J. A. T.; Paul, D. McK.; Hillier, A. D.; Singh, R. P.

    2018-03-01

    We have investigated the superconducting state of the noncentrosymmetric superconductor Re6Ti (Tc=6.0 K) using a muon-spin rotation/relaxation technique. The zero-field muon experiment shows the presence of spontaneous magnetic fields in the superconducting state, indicating time-reversal symmetry breaking (TRSB). However, the low-temperature transverse-field muon measurements suggest nodeless s -wave superconductivity. Similar results were also observed for Re6X (X =Zr , Hf) family of materials which indicates that the pairing symmetry does not depend on the spin-orbital coupling. Altogether, these studies suggest an unconventional nature (TRSB) of superconductivity is intrinsic to the Re6X family of compounds and paves the way for further studies of this family of materials.

  12. Relation between PT -symmetry breaking and topologically nontrivial phases in the Su-Schrieffer-Heeger and Kitaev models

    Science.gov (United States)

    Klett, Marcel; Cartarius, Holger; Dast, Dennis; Main, Jörg; Wunner, Günter

    2017-05-01

    Non-Hermitian systems with PT symmetry can possess purely real eigenvalue spectra. In this work two one-dimensional systems with two different topological phases, the topological nontrivial phase (TNP) and the topological trivial phase (TTP), combined with PT -symmetric non-Hermitian potentials are investigated. The models of choice are the Su-Schrieffer-Heeger (SSH) model and the Kitaev chain. The interplay of a spontaneous PT -symmetry breaking due to gain and loss with the topological phase is different for the two models. The SSH model undergoes a PT -symmetry breaking transition in the TNP immediately with the presence of a nonvanishing gain and loss strength γ , whereas the TTP exhibits a parameter regime in which a purely real eigenvalue spectrum exists. For the Kitaev chain the PT -symmetry breaking is independent of the topological phase. We show that the topologically interesting states—the edge states—are the reason for the different behaviors of the two models and that the intrinsic particle-hole symmetry of the edge states in the Kitaev chain is responsible for a conservation of PT symmetry in the TNP.

  13. Spontaneous symmetry breaking on a mutiple-channel hollow cylinder

    Science.gov (United States)

    Wang, Ruili; Kolomeisky, Anatoly B.; Liu, Mingzhe

    2011-01-01

    This Letter investigates coupled asymmetric exclusion processes with two types of particles on multiple parallel channels of a hollow cylinder. The model is inspired by the structure of microtubules, along which motor proteins such as kinesins and dyneins move in opposite directions. Interactions between two-species particles are assumed to take place only on the left and right boundaries where a rule of narrow entrances is applied. Narrow entrances mean that a particle cannot enter the system if either of two nearest-neighbor sites on the neighboring channels is occupied by a particle of the other species. This rule is similar to, but different from, that in [E. Pronina, A.B. Kolomeisky, J. Phys. A 40 (2007) 2275] since the narrow entrance rule in our model involves two neighbors. The phase diagram of our model is studied theoretically and via Monte Carlo simulations. The spontaneous symmetry breaking (SSB) is observed in the system. There are four possible phases in the system and with SSB occurring in two of them: high/low density and asymmetric low/low density. Bulk density and particle currents are also computed. Theoretical calculations deviate from Monte Carlo simulation results due to the neglecting of correlations in particles dynamics in mean-field analysis.

  14. Natural Cold Baryogenesis from Strongly Interacting Electroweak Symmetry Breaking

    CERN Document Server

    Konstandin, Thomas

    2011-01-01

    The mechanism of "cold electroweak baryogenesis" has been so far unpopular because its proposal has relied on the ad-hoc assumption of a period of hybrid inflation at the electroweak scale with the Higgs acting as the waterfall field. We argue here that cold baryogenesis can be naturally realized without the need to introduce any slow-roll potential. Our point is that composite Higgs models where electroweak symmetry breaking arises via a strongly first-order phase transition provide a well-motivated framework for cold baryogenesis. In this case, reheating proceeds by bubble collisions and we argue that this can induce changes in Chern-Simons number, which in the presence of new sources of CP violation commonly lead to baryogenesis. We illustrate this mechanism using as a source of CP violation an effective dimension-six operator which is free from EDM constraints, another advantage of cold baryogenesis compared to the standard theory of electroweak baryogenesis. Our results are general as they do not rely on...

  15. Supplies in gravitational dynamics and electroweak symmetry breaking

    International Nuclear Information System (INIS)

    Soldate, M.

    1988-01-01

    During the past few years, my research interests have centered on physics associated with the Planck and electroweak scales. In each instance there is a physical issue which has motivated my work. The first is the dynamical determination of the observed geometry of spacetime. Typically, in a theory of quantum gravity, the topology and long-distance geometry of spacetime are not fixed uniquely by the field equations. One would like to be able to determine them through a dynamical principle for predictive power. The matter is of particular relevance to superstring theories, as they are most simply formulated in 10-dimensional Minkowski space. The second topic is the origin of electroweak symmetry breaking (EWSB). My work here has tended to be more phenomenological; it appears unlikely that a complete understanding of the gauge hierarchy problem can be obtained without some experimental knowledge of particles rather directly related to EWSB. I feel that both of these issues are of broad interest. In this paper, I will describe my future research plans in these areas after motivating and summarizing my previous work on them. 22 refs

  16. A perfectly conducting surface in electrodynamics with Lorentz symmetry breaking

    Science.gov (United States)

    Borges, L. H. C.; Barone, F. A.

    2017-10-01

    In this paper we consider a model which exhibits explicit Lorentz symmetry breaking due to the presence of a single background vector v^{μ } coupled to the gauge field. We investigate such a theory in the vicinity of a perfectly conducting plate for different configurations of v^{μ }. First we consider no restrictions on the components of the background vector and we treat it perturbatively up to second order. Next, we treat v^{μ } exactly for two special cases: the first one is when it has only components parallel to the plate, and the second one when it has a single component perpendicular to the plate. For all these configurations, the propagator for the gauge field and the interaction force between the plate and a point-like electric charge are computed. Surprisingly, it is shown that the image method is valid in our model and we argue that it is a non-trivial result. We show there arises a torque on the mirror with respect to its positioning in the background field when it interacts with a point-like charge. It is a new effect with no counterpart in theories with Lorentz symmetry in the presence of a perfect mirror.

  17. A perfectly conducting surface in electrodynamics with Lorentz symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Borges, L.H.C. [UNESP, Campus de Guaratingueta, DFQ, Guaratingueta, SP (Brazil); Barone, F.A. [IFQ, Universidade Federal de Itajuba, Itajuba, MG (Brazil)

    2017-10-15

    In this paper we consider a model which exhibits explicit Lorentz symmetry breaking due to the presence of a single background vector v{sup μ} coupled to the gauge field. We investigate such a theory in the vicinity of a perfectly conducting plate for different configurations of v{sup μ}. First we consider no restrictions on the components of the background vector and we treat it perturbatively up to second order. Next, we treat v{sup μ} exactly for two special cases: the first one is when it has only components parallel to the plate, and the second one when it has a single component perpendicular to the plate. For all these configurations, the propagator for the gauge field and the interaction force between the plate and a point-like electric charge are computed. Surprisingly, it is shown that the image method is valid in our model and we argue that it is a non-trivial result. We show there arises a torque on the mirror with respect to its positioning in the background field when it interacts with a point-like charge. It is a new effect with no counterpart in theories with Lorentz symmetry in the presence of a perfect mirror. (orig.)

  18. Spontaneous symmetry breaking in vortex systems with two repulsive lengthscales.

    Science.gov (United States)

    Curran, P J; Desoky, W M; Milosević, M V; Chaves, A; Laloë, J-B; Moodera, J S; Bending, S J

    2015-10-23

    Scanning Hall probe microscopy (SHPM) has been used to study vortex structures in thin epitaxial films of the superconductor MgB2. Unusual vortex patterns observed in MgB2 single crystals have previously been attributed to a competition between short-range repulsive and long-range attractive vortex-vortex interactions in this two band superconductor; the type 1.5 superconductivity scenario. Our films have much higher levels of disorder than bulk single crystals and therefore both superconducting condensates are expected to be pushed deep into the type 2 regime with purely repulsive vortex interactions. We observe broken symmetry vortex patterns at low fields in all samples after field-cooling from above Tc. These are consistent with those seen in systems with competing repulsions on disparate length scales, and remarkably similar structures are reproduced in dirty two band Ginzburg-Landau calculations, where the simulation parameters have been defined by experimental observations. This suggests that in our dirty MgB2 films, the symmetry of the vortex structures is broken by the presence of vortex repulsions with two different lengthscales, originating from the two distinct superconducting condensates. This represents an entirely new mechanism for spontaneous symmetry breaking in systems of superconducting vortices, with important implications for pinning phenomena and high current density applications.

  19. A pedagogical review of electroweak symmetry breaking scenarios

    International Nuclear Information System (INIS)

    Bhattacharyya, Gautam

    2011-01-01

    We review different avenues of electroweak symmetry breaking explored over the years. This constitutes a timely exercise as the world's largest and the highest energy particle accelerator, namely, the Large Hadron Collider (LHC) at CERN near Geneva, has started running whose primary mission is to find the Higgs or some phenomena that mimic the effects of the Higgs, i.e. to unravel the mysteries of electroweak phase transition. In the beginning, we discuss the Standard Model Higgs mechanism. After that we review the Higgs sector of the minimal supersymmetric Standard Model. Then we take up three relatively recent ideas: little Higgs, gauge-Higgs unification and Higgsless scenarios. For the latter three cases, we first present the basic ideas and restrict our illustration to some instructive toy models to provide an intuitive feel of the underlying dynamics, and then discuss, for each of the three cases, how more realistic scenarios are constructed and how to decipher their experimental signatures. Wherever possible, we provide pedagogical details, which beginners might find useful.

  20. Robustness of replica symmetry breaking phenomenology in random laser.

    Science.gov (United States)

    Tommasi, Federico; Ignesti, Emilio; Lepri, Stefano; Cavalieri, Stefano

    2016-11-16

    Random lasers are optical sources where light is amplified by stimulated emission along random paths through an amplifying scattering medium. Connections between their physics and the one of quenched disordered nonlinear systems, notably spin glasses, have been recently suggested. Here we report a first experimental study of correlations of spectral fluctuations intensity in a random laser medium where the scatterers displacement significantly changes among consecutive shots. Remarkably, our results reveal that the replica symmetry breaking (RSB) phenomenology is robust with respect to an averaging over different realizations of the disorder. Moreover, besides opening new intriguing questions about the understanding of such a phenomenon, this work aims to clarify the connection between the RSB with the onset of the Lévy regime, i.e. the fluctuations regime that is a peculiar feature of the random lasing under critical conditions. Our results suggest that the former occurs independently of the latter and then the RSB phenomenology is a generic feature linked to the random laser threshold.

  1. Emergent spontaneous symmetry breaking and emergent symmetry restoration in rippling gravitational background

    Energy Technology Data Exchange (ETDEWEB)

    Kurkov, Maxim A. [Universidade Federal do ABC, CMCC, Santo Andre, SP (Brazil)

    2016-06-15

    We study effects of a rippling gravitational background on a scalar field with a double well potential, focusing on the analogy with the well known dynamics of the Kapitza's pendulum. The ripples are rendered as infinitesimal but rapidly oscillating perturbations of the scale factor. We find that the resulting dynamics crucially depends on a value of the parameter ξ in the ξRφ{sup 2} vertex. For the time-dependent perturbations of a proper form the resulting effective action is generally covariant, and at a high enough frequency at ξ < 0 and at ξ > 1/6 the effective potential has a single minimum at zero, thereby restoring spontaneously broken symmetry of the ground state. On the other side, at 0 < ξ < 1/6 spontaneous symmetry breaking emerges even when it is absent in the unperturbed case. (orig.)

  2. New improved derivative expansion for field theories with spontaneous symmetry breaking

    International Nuclear Information System (INIS)

    Chan, Lai-Him.

    1994-01-01

    Derivative expansion of the effective action for field theories with spontaneous symmetry breaking may be badly divergent. I propose a new expansion series in which the series expansion are simultaneous developed in order of the number of derivatives of the field and in power of the deviation of the field from its ground state value. As examples, I have applied this new method to calculate the quantum correction to the energy of the 1+1 dimension soliton in various models. For the models in which exact solutions have been found, such as the Sine-Gordon soliton, φ 4 soliton, and φ 4 soliton with fermion loop, the improved series can be recognized as well-known analytically summable series. The results of the exact solutions are completely recovered. More importantly, for the cases where exact solutions may not be available, Pade approximant or the Borel summation can be used to give good approximation

  3. Enhanced Circular Dichroism via Symmetry Breaking in a Chiral Plasmonic Nanoparticle Oligomer

    Science.gov (United States)

    Le, Khai Q.

    2018-02-01

    A chiral plasmonic nanoparticle oligomer, consisting of four symmetrically arranged nanodisks of different heights and having different optical absorption responses to left and right-handed circularly polarized light illumination, has been experimentally reported in the literature. The resulting circular dichroism (CD) signal was detectable with state of the art CD spectrometers but was much weaker than those of existing chiral nanostructures, i.e., three-dimensional (3-D) chiral metamaterials. In this letter, via symmetry breaking in such an oligomer, the author demonstrates that the CD can be enhanced up to six times compared to that of a symmetric oligomer, and is in the range of a relevant 3-D chiral metamolecule. Through investigation of geometrical parameters including particle size, asymmetric and symmetric gaps, the CD evolution was reported, which provides a useful guideline for design of two-dimensional chiral oligomers adopted as efficient probes for CD spectroscopic applications.

  4. Charge symmetry breaking in dd→He4π0 with WASA-at-COSY

    Directory of Open Access Journals (Sweden)

    P. Adlarson

    2014-12-01

    Full Text Available Charge symmetry breaking (CSB observables are a suitable experimental tool to examine effects induced by quark masses on the nuclear level. Previous high precision data from TRIUMF and IUCF are currently used to develop a consistent description of CSB within the framework of chiral perturbation theory. In this work the experimental studies on the reaction dd→He4π0 have been extended towards higher excess energies in order to provide information on the contribution of p-waves in the final state. For this, an exclusive measurement has been carried out at a beam momentum of pd=1.2 GeV/c using the WASA-at-COSY facility. The total cross section amounts to σtot=(118±18stat±13sys±8ext pb and first data on the differential cross section are consistent with s-wave pion production.

  5. Spontaneous Symmetry-Breaking in a Network Model for Quadruped Locomotion

    Science.gov (United States)

    Stewart, Ian

    2017-12-01

    Spontaneous symmetry-breaking proves a mechanism for pattern generation in legged locomotion of animals. The basic timing patterns of animal gaits are produced by a network of spinal neurons known as a Central Pattern Generator (CPG). Animal gaits are primarily characterized by phase differences between leg movements in a periodic gait cycle. Many different gaits occur, often having spatial or spatiotemporal symmetries. A natural way to explain gait patterns is to assume that the CPG is symmetric, and to classify the possible symmetry-breaking periodic motions. Pinto and Golubitsky have discussed a four-node model CPG network for biped gaits with ℤ2 × ℤ2 symmetry, classifying the possible periodic states that can arise. A more specific rate model with this structure has been analyzed in detail by Stewart. Here we extend these methods to quadruped gaits, using an eight-node network with ℤ4 × ℤ2 symmetry proposed by Golubitsky and coworkers. We formulate a rate model and calculate how the first steady or Hopf bifurcation depends on its parameters, which represent four connection strengths. The calculations involve a distinction between “real” gaits with one or two phase shifts (pronk, bound, pace, trot) and “complex” gaits with four phase shifts (forward and reverse walk, forward and reverse buck). The former correspond to real eigenvalues of the connection matrix, the latter to complex conjugate pairs. The partition of parameter space according to the first bifurcation, ignoring complex gaits, is described explicitly. The complex gaits introduce further complications, not yet fully understood. All eight gaits can occur as the first bifurcation from a fully synchronous equilibrium, for suitable parameters, and numerical simulations indicate that they can be asymptotically stable.

  6. No-go for tree-level R-symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Feihu [University of Electronic Science and Technology of China, School of Physical Electronics, Chengdu (China); Liu, Muyang [Sichuan University, Center for Theoretical Physics, College of Physical Science and Technology, Chengdu (China); Sun, Zheng [Sichuan University, Center for Theoretical Physics, College of Physical Science and Technology, Chengdu (China); Chinese Academy of Sciences, CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Beijing (China)

    2017-11-15

    We show that in gauge mediation models with tree-level R-symmetry breaking where supersymmetry and R-symmetries are broken by different fields, the gaugino mass either vanishes at one loop or finds a contribution from loop-level R-symmetry breaking. Thus tree-level R-symmetry breaking for phenomenology is either no-go or redundant in the simplest type of models. Including explicit messenger mass terms in the superpotential with a particular R-charge arrangement is helpful to bypass the no-go theorem, and the resulting gaugino mass is suppressed by the messenger mass scale. (orig.)

  7. Spontaneous Symmetry Breaking and Nambu-Goldstone Bosons in Quantum Many-Body Systems

    Czech Academy of Sciences Publication Activity Database

    Brauner, Tomáš

    2010-01-01

    Roč. 2, č. 2 (2010), s. 609-657 ISSN 2073-8994 Institutional support: RVO:61389005 Keywords : spontaneous symmetry breaking * Nambu-Goldstone bosons * effective field theory Subject RIV: BE - Theoretical Physics

  8. Controlling Long-Lived Triplet Generation from Intramolecular Singlet Fission in the Solid State

    KAUST Repository

    Pace, Natalie A.

    2017-11-30

    The conjugated polymer poly(benzothiophene dioxide) (PBTDO1) has recently been shown to exhibit efficient intramolecular singlet fission in solution. In this paper, we investigate the role of intermolecular interactions in triplet separation dynamics after singlet fission. We use transient absorption spectroscopy to determine the singlet fission rate and triplet yield in two polymers differing only by side chain motif in both solution and the solid state. Whereas solid-state films show singlet fission rates identical to those measured in solution, the average lifetime of the triplet population increases dramatically, and is strongly dependent on side-chain identity. These results show that it may be necessary to carefully engineer the solid-state microstructure of these “singlet fission polymers” in order to produce the long-lived triplets needed to realize efficient photovoltaic devices.

  9. Topological symmetry breaking of self-interacting fractional Klein-Gordon field theories on toroidal spacetime

    International Nuclear Information System (INIS)

    Lim, S C; Teo, L P

    2008-01-01

    Quartic self-interacting fractional Klein-Gordon scalar massive and massless field theories on toroidal spacetime are studied. The effective potential and topologically generated mass are determined using zeta-function regularization technique. Renormalization of these quantities are derived. Conditions for symmetry breaking are obtained analytically. Simulations are carried out to illustrate regions or values of compactified dimensions where symmetry-breaking mechanisms appear

  10. Spin-singlet quantum Hall states and Jack polynomials with a prescribed symmetry

    International Nuclear Information System (INIS)

    Estienne, Benoit; Bernevig, B. Andrei

    2012-01-01

    We show that a large class of bosonic spin-singlet Fractional Quantum Hall model wavefunctions and their quasihole excitations can be written in terms of Jack polynomials with a prescribed symmetry. Our approach describes new spin-singlet quantum Hall states at filling fraction ν=(2k)/(2r-1) and generalizes the (k,r) spin-polarized Jack polynomial states. The NASS and Halperin spin-singlet states emerge as specific cases of our construction. The polynomials express many-body states which contain configurations obtained from a root partition through a generalized squeezing procedure involving spin and orbital degrees of freedom. The corresponding generalized Pauli principle for root partitions is obtained, allowing for counting of the quasihole states. We also extract the central charge and quasihole scaling dimension, and propose a conjecture for the underlying CFT of the (k,r) spin-singlet Jack states.

  11. Zurek–Kibble Symmetry Breaking Process in Superconducting Rings; Spontaneous Fluxon Formation in Annular Josephson Tunnel Junctions

    DEFF Research Database (Denmark)

    Aarøe, Morten; Monaco, Roberto; Dmitriev, P

    2007-01-01

    We report on new investigations of spontaneous symmetry breaking in non-adiabatic phase transitions. This Zurek-Kibble (ZK) process is mimicked in solid state systems by trapping of magnetic flux quanta, fluxons, in a long annular Josephson tunnel junction quenched through the normal.......5 for the ZK critical scaling exponent sigma, which does not agree with an earlier theoretical prediction of sigma = 0.25. A novel theory based on the proximity effect leading to sigma = 0.50 has been proposed. The dependence of the gap voltage on temperature is measured and used for precise monitoring...

  12. Chiral Symmetry Breaking in Peptide Systems During Formation of Life on Earth

    Science.gov (United States)

    Konstantinov, Konstantin K.; Konstantinova, Alisa F.

    2018-03-01

    Chiral symmetry breaking in complex chemical systems with a large number of amino acids and a large number of similar reactions was considered. It was shown that effective averaging over similar reaction channels may result in very weak effective enantioselectivity of forward reactions, which does not allow most of the known models to result in chiral symmetry breaking during formation of life on Earth. Models with simple and catalytic synthesis of a single amino acid, formation of peptides up to length five, and sedimentation of insoluble pair of substances were considered. It was shown that depending on the model and the values of the parameters, chiral symmetry breaking may occur in up to about 10% out of all possible unique insoluble pair combinations even in the absence of any catalytic synthesis and that minimum total number of amino acids in the pair is 5. If weak enantioselective forward catalytic synthesis of amino acids is present, then the number of possible variants, in which chiral symmetry breaking may occur, increases substantially. It was shown that that the most interesting catalysts have zero or one amino acid of "incorrect" chirality. If the parameters of the model are adjusted in such a way to result in an increase of concentration of longer peptides, then catalysts with two amino acids of incorrect chirality start to appear at peptides of length five. Models of chiral symmetry breaking in the presence of epimerization were considered for peptides up to length three. It was shown that the range of parameters in which chiral symmetry breaking could occur significantly shrinks in comparison to previously considered models with peptides up to length two. An experiment of chiral symmetry breaking was proposed. The experiment consists of a three-step cycle: reversible catalytic synthesis of amino acids, reversible synthesis of peptides, and irreversible sedimentation of insoluble substances.

  13. Nuclear spin singlet states as a contrast mechanism for NMR spectroscopy.

    Science.gov (United States)

    Devience, Stephen J; Walsworth, Ronald L; Rosen, Matthew S

    2013-10-01

    Nuclear magnetic resonance (NMR) spectra of complex chemical mixtures often contain unresolved or hidden spectral components, especially when strong background signals overlap weaker peaks. In this article we demonstrate a quantum filter utilizing nuclear spin singlet states, which allows undesired NMR spectral background to be removed and target spectral peaks to be uncovered. The quantum filter is implemented by creating a nuclear spin singlet state with spin quantum numbers j = 0, mz  = 0 in a target molecule, applying a continuous RF field to both preserve the singlet state and saturate the magnetization of undesired molecules and then mapping the target molecule singlet state back into an NMR observable state so that its spectrum can be read out unambiguously. The preparation of the target singlet state can be carefully controlled with pulse sequence parameters, so that spectral contrast can be achieved between molecules with very similar structures. We name this NMR contrast mechanism 'Suppression of Undesired Chemicals using Contrast-Enhancing Singlet States' (SUCCESS) and we demonstrate it in vitro for three target molecules relevant to neuroscience: aspartate, threonine and glutamine. Copyright © 2013 John Wiley & Sons, Ltd.

  14. Is radiative electroweak symmetry breaking consistent with a 125 GeV Higgs mass?

    Science.gov (United States)

    Steele, T G; Wang, Zhi-Wei

    2013-04-12

    The mechanism of radiative electroweak symmetry breaking occurs through loop corrections, and unlike conventional symmetry breaking where the Higgs mass is a parameter, the radiatively generated Higgs mass is dynamically predicted. Padé approximations and an averaging method are developed to extend the Higgs mass predictions in radiative electroweak symmetry breaking from five- to nine-loop order in the scalar sector of the standard model, resulting in an upper bound on the Higgs mass of 141 GeV. The mass predictions are well described by a geometric series behavior, converging to an asymptotic Higgs mass of 124 GeV consistent with the recent ATLAS and CMS Collaborations observations. Similarly, we find that the Higgs self-coupling converges to λ=0.23, which is significantly larger than its conventional symmetry breaking counterpart for a 124 GeV Higgs mass. In addition to this significant enhancement of the Higgs self-coupling and HH→HH scattering, we find that Higgs decays to gauge bosons are unaltered and the scattering processes WL(+)WL(+)→HH, ZLZL→HH are also enhanced, providing signals to distinguish conventional and radiative electroweak symmetry breaking mechanisms.

  15. Symmetry Breaking of B2N((-, 0, +)): An Aspect of the Electric Potential and Atomic Charges.

    Science.gov (United States)

    Monajjemi, Majid; Bagheri, Samira; Moosavi, Matin S; Moradiyeh, Nahid; Zakeri, Mina; Attarikhasraghi, Naime; Saghayimarouf, Nastaran; Niyatzadeh, Ghorban; Shekarkhand, Marzie; Khalilimofrad, Mohammad S; Ahmadin, Hashem; Ahadi, Maryam

    2015-12-03

    In this study, the three forms of B2N((-, 0, +))-radical, anion and cation-have been compared in terms of electric potential and atomic charges, ESP, rather than the well-known cut of the potential energy surface (PES). We have realized that the double minimum of the BNB radical is related to the lack of the correct permutational symmetry of the wave function and charge distribution. The symmetry breaking (SB) for B2N((0, +)) exhibits energy barrier in the region of (5-150) cm(-1). The SB barrier goes through a dynamic change with no centrosymmetric form which depends on the wave function or charge distribution. In spite of A ˜ 2 Σ g + exited state, the B ˜ 2 ∏ g excited configuration contributes to the ground state ( B ˜ 2 ∏ g - X ˜ 2 Σ u + ) for forming radicals. The SB did not occur for the anion form (B2N((-))) in any electrostatic potential and charges distribution. Finally, we have modified the Columbic term of the Schrödinger equation to define the parameters "αα' and ββ'" in order to investigate the SBs subject.

  16. Moving vortex phases, dynamical symmetry breaking, and jamming for vortices in honeycomb pinning arrays

    Energy Technology Data Exchange (ETDEWEB)

    Reichhardt, Charles [Los Alamos National Laboratory; Reichhardt, Cynthia [Los Alamos National Laboratory

    2008-01-01

    We show using numerical simulations that vortices in honeycomb pinning arrays can exhibit a remarkable variety of dynamical phases that are distinct from those found for triangular and square pinning arrays. In the honeycomb arrays, it is possible for the interstitial vortices to form dimer or higher n-mer states which have an additional orientational degree of freedom that can lead to the formation of vortex molecular crystals. For filling fractions where dimer states appear, a dynamical symmetry breaking can occur when the dimers flow in one of two possible alignment directions. This leads to transport in the direction transverse to the applied drive. We show that dimerization produces distinct types of moving phases which depend on the direction of the driving force with respect to the pinning lattice symmetry. When the dimers are driven along certain directions, a reorientation of the dimers can produce a jamming phenomenon which results in a strong enhancement in the critical depinning force. The jamming can also cause unusual effects such as an increase in the critical depinning force when the size of the pinning sites is reduced.

  17. Spatial and Spin Symmetry Breaking in Semidefinite-Programming-Based Hartree-Fock Theory.

    Science.gov (United States)

    Nascimento, Daniel R; DePrince, A Eugene

    2018-04-16

    The Hartree-Fock problem was recently recast as a semidefinite optimization over the space of rank-constrained two-body reduced-density matrices (RDMs) [ Phys. Rev. A 2014 , 89 , 010502(R) ]. This formulation of the problem transfers the nonconvexity of the Hartree-Fock energy functional to the rank constraint on the two-body RDM. We consider an equivalent optimization over the space of positive semidefinite one-electron RDMs (1-RDMs) that retains the nonconvexity of the Hartree-Fock energy expression. The optimized 1-RDM satisfies ensemble N-representability conditions, and ensemble spin-state conditions may be imposed as well. The spin-state conditions place additional linear and nonlinear constraints on the 1-RDM. We apply this RDM-based approach to several molecular systems and explore its spatial (point group) and spin ( Ŝ 2 and Ŝ 3 ) symmetry breaking properties. When imposing Ŝ 2 and Ŝ 3 symmetry but relaxing point group symmetry, the procedure often locates spatial-symmetry-broken solutions that are difficult to identify using standard algorithms. For example, the RDM-based approach yields a smooth, spatial-symmetry-broken potential energy curve for the well-known Be-H 2 insertion pathway. We also demonstrate numerically that, upon relaxation of Ŝ 2 and Ŝ 3 symmetry constraints, the RDM-based approach is equivalent to real-valued generalized Hartree-Fock theory.

  18. Symmetry breaking and the fermionic fractional Chern insulator in topologically trivial bands

    Science.gov (United States)

    Kourtis, Stefanos

    2018-02-01

    We describe a mechanism by which fermions in topologically trivial bands can form correlated states exhibiting a fractional quantum Hall (FQH) effect upon introduction of strong repulsive interactions. These states are solid-liquid composites, in which a FQH liquid is induced by the formation of charge order (CO), following a recently proposed paradigm of symmetry-breaking topological (SBT) order [Phys. Rev. Lett. 113, 216404 (2014), 10.1103/PhysRevLett.113.216404]. We devise a spinless fermion model on a triangular lattice, featuring a topologically trivial phase when interactions are omitted. Adding strong short-range repulsion, we first establish a repulsion-driven CO phase at density ρCO=2 /3 particles per site, then dope the model to higher densities ρ =ρCO+ν /6 . At ν =1 /3 ,2 /5 (ρ =13 /18 ,11 /15 ) we observe definitive signatures of both CO and the FQH effect—a sharply peaked static structure factor, gapped and degenerate energy spectrum, and fractionally quantized Hall conductivity σH=1 /3 ,2 /5 in units of e2/h —over a range of all model parameters. We thus obtain direct evidence for fermionic SBT order of FQH type in topologically trivial bands.

  19. Control of the symmetry breaking in double-well potentials by the resonant nonlinearity management

    International Nuclear Information System (INIS)

    Nistazakis, H. E.; Frantzeskakis, D. J.; Malomed, B. A.; Kevrekidis, P. G.

    2011-01-01

    We introduce a one-dimensional model of Bose-Einstein condensates (BECs), combining the double-well potential, which is a usual setting for the onset of spontaneous-symmetry-breaking (SSB) effects, and time-periodic modulation of the nonlinearity, which may be implemented by means of the Feshbach-resonance-management (FRM) technique. Both cases of the nonlinearity that is repulsive or attractive on the average are considered. In the former case, the main effect produced by the application of the FRM is spontaneous self-trapping of the condensate in either of the two potential wells in parameter regimes where it would remain untrapped in the absence of the management. In the weakly nonlinear regime, the frequency of intrinsic oscillations in the FRM-induced trapped state is very close to half the FRM frequency, suggesting that the effect is accounted for by a parametric resonance. In the case of the attractive nonlinearity, the FRM-induced effect is the opposite, i.e., enforced detrapping of a state which is self-trapped in its unmanaged form. In the latter case, the frequency of oscillations of the untrapped mode is close to a quarter of the driving frequency, suggesting that a higher-order parametric resonance may account for this effect.

  20. Cooperation and competition between two symmetry breakings in a coupled ratchet

    Science.gov (United States)

    Li, Chen-Pu; Chen, Hong-Bin; Fan, Hong; Xie, Ge-Ying; Zheng, Zhi-Gang

    2018-03-01

    We investigate the collective mechanism of coupled Brownian motors in a flashing ratchet in the presence of coupling symmetry breaking and space symmetry breaking. The dependences of directed current on various parameters are extensively studied in terms of numerical simulations and theoretical analysis. Reversed motion can be achieved by modulating multiple parameters including the spatial asymmetry coefficient, the coupling asymmetry coefficient, the coupling free length and the coupling strength. The dynamical mechanism of these transport properties can be reasonably explained by the effective potential theory and the cooperation or competition between two symmetry breakings. Moreover, adjusting the Gaussian white noise intensity, which can induce weak reversed motion under certain condition, can optimize and manipulate the directed transport of the ratchet system.

  1. Marangoni-induced symmetry-breaking pattern selection on viscous fluids

    Science.gov (United States)

    Shen, Li; Denner, Fabian; Morgan, Neal; van Wachem, Berend; Dini, Daniele

    2016-11-01

    Symmetry breaking transitions on curved surfaces are found in a wide range of dissipative systems, ranging from asymmetric cell divisions to structure formation in thin films. Inherent within the nonlinearities are the associated curvilinear geometry, the elastic stretching, bending and the various fluid dynamical processes. We present a generalised Swift-Hohenberg pattern selection theory on a thin, curved and viscous films in the presence of non-trivial Marangoni effect. Testing the theory with experiments on soap bubbles, we observe the film pattern selection to mimic that of the elastic wrinkling morphology on a curved elastic bilayer in regions of slow viscous flow. By examining the local state of damping of surface capillary waves we attempt to establish an equivalence between the Marangoni fluid dynamics and the nonlinear elastic shell theory above the critical wavenumber of the instabilities and propose a possible explanation for the perceived elastic-fluidic duality. The authors acknowledge the financial support of the Shell University Technology Centre for fuels and lubricants.

  2. Comments on the Chiral Symmetry Breaking in Soft Wall Holographic QCD

    DEFF Research Database (Denmark)

    Bechi, Jacopo

    2009-01-01

    In this paper we describe qualitatively some aspects of the holographic QCD. Inspired by a successfull 4D description, we try to separate the Confinement and the Chiral Symmetry Breaking dynamics. We also discuss the realization of the baryons as skyrmions in Soft Wall Holographic QCD, and the is......In this paper we describe qualitatively some aspects of the holographic QCD. Inspired by a successfull 4D description, we try to separate the Confinement and the Chiral Symmetry Breaking dynamics. We also discuss the realization of the baryons as skyrmions in Soft Wall Holographic QCD...

  3. Pursuing the origin of electroweak symmetry breaking: a 'Bayesian Physics' argument for a √s ∼+e- collider

    International Nuclear Information System (INIS)

    Kane, G.L.; Wells, James D.

    2000-01-01

    High-energy data has been accumulating over the last ten years, and it should not be ignored when making decisions about the future experimental program. In particular, we argue that the electroweak data collected at LEP, SLC and Tevatron indicate a light scalar particle with mass less than 500 GeV. This result is based on considering a wide variety of theories including the Standard Model, supersymmetry, large extra dimensions, and composite models. We argue that a high luminosity, 600 GeV e + e - collider would then be the natural choice to feel confident about finding and studying states connected to electroweak symmetry breaking. We also argue from the data that worrying about resonances at multi-TeV energies as the only signal for electroweak symmetry breaking is not as important a discovery issue for the next generation of colliders. Such concerns should perhaps be replaced with more relevant discovery issues such as a Higgs boson that decays invisibly, and ''new physics'' that could conspire with a heavier Higgs boson to accommodate precision electroweak data. An e + e - collider with √s ∼< 600 GeV is ideally suited to cover these possibilities

  4. Interplay between singlet and triplet excited states in a conformationally locked donor–acceptor dyad

    KAUST Repository

    Filatov, Mikhail A.

    2015-10-13

    The synthesis and photophysical characterization of a palladium(II) porphyrin – anthracene dyad bridged via short and conformationally rigid bicyclo[2.2.2]octadiene spacer were achieved. A spectroscopic investigation of the prepared molecule in solution has been undertaken to study electronic energy transfer in excited singlet and triplet states between the anthracene and porphyrin units. By using steady-state and time-resolved photoluminescence spectroscopy it was shown that excitation of the singlet excited state of the anthracene leads to energy transfer to the lower-lying singlet state of porphyrin. Alternatively, excitation of the porphyrin followed by intersystem crossing to the triplet state leads to very fast energy transfer to the triplet state of anthracene. The rate of this energy transfer has been determined by transient absorption spectroscopy. Comparative studies of the dynamics of triplet excited states of the dyad and reference palladium octaethylporphyrin (PdOEP) have been performed.

  5. Field-induced cluster spin glass and inverse symmetry breaking enhanced by frustration

    Science.gov (United States)

    Schmidt, M.; Zimmer, F. M.; Magalhaes, S. G.

    2018-03-01

    We consider a cluster disordered model to study the interplay between short- and long-range interactions in geometrically frustrated spin systems under an external magnetic field (h). In our approach, the intercluster long-range disorder (J) is analytically treated to get an effective cluster model that is computed exactly. The clusters follow a checkerboard lattice with first-neighbor (J1) and second-neighbor (J2) interactions. We find a reentrant transition from the cluster spin-glass (CSG) state to a paramagnetic (PM) phase as the temperature decreases for a certain range of h. This inverse symmetry breaking (ISB) appears as a consequence of both quenched disorder with frustration and h, that introduce a CSG state with higher entropy than the polarized PM phase. The competitive scenario introduced by antiferromagnetic (AF) short-range interactions increases the CSG state entropy, leading to continuous ISB transitions and enhancing the ISB regions, mainly in the geometrically frustrated case (J1 =J2). Remarkably, when strong AF intracluster couplings are present, field-induced CSG phases can be found. These CSG regions are strongly related to the magnetization plateaus observed in this cluster disordered system. In fact, it is found that each field-induced magnetization jump brings a CSG region. We notice that geometrical frustration, as well as cluster size, play an important role in the magnetization plateaus and, therefore, are also relevant in the field-induced glassy states. Our findings suggest that competing interactions support ISB and field-induced CSG phases in disordered cluster systems under an external magnetic field.

  6. Supersymmetric singlet majorons and cosmology

    International Nuclear Information System (INIS)

    Chun, E.J.; Kim, H.B.; Lukas, A.

    1994-02-01

    We examine cosmological constraints on the lepton number breaking scale in super-symmetric singlet majoron models. Special attention is drawn to the model dependence arising from the particular choice of a certain majoron extension and a cosmological scenario. We find that the bounds on the symmetry breaking scale can vary substantially. Large values of this scale can be allowed if the decoupling temperature of majoron and majorino exceeds the reheating temperature of inflation. In the opposite case an upper bound depending on the majoron model can be obtained which, however, is unlikely to be much larger than 10 10 GeV. (author). 13 refs, 2 figs

  7. Aspects of semilocal BPS vortex in systems with Lorentz symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Villalobos, C.H.C.; Silva, J.M.H. da; Hott, M.B. [UNESP, Univ Estadual Paulista, Departamento de Fisica e Quimica, Guaratingueta, SP (Brazil); Belich, H. [Universidade Federal do Espi rito Santo (UFES), Departamento de Fisica e Quimica, Vitoria, ES (Brazil)

    2014-03-15

    The existence is shown of a static self-dual semilocal vortex configuration for the Maxwell-Higgs system with a Lorentz-violating CPT-even term. The dependence of the vorticity upper limit on the Lorentz-symmetry-breaking term is also investigated. (orig.)

  8. Spontaneous symmetry breaking and self-consistent equations for the free-energy

    International Nuclear Information System (INIS)

    Lovesey, S.W.

    1980-03-01

    A variational procedure for the free-energy is used to derive self-consistent equations that allow for spontaneous symmetry breaking. For an N-component phi 4 -model the equations are identical to those obtained by summing all loops to order 1/N. (author)

  9. Sequence selection by dynamical symmetry breaking in an autocatalytic binary polymer model

    DEFF Research Database (Denmark)

    Fellermann, Harold; Tanaka, Shinpei; Rasmussen, Steen

    2017-01-01

    the appearance of a few population structures with highly ordered and repetitive sequence patterns when starting from a pool of monomers. We demonstrate both analytically and through simulation how this "selection of the dullest" is caused by continued symmetry breaking through random fluctuations...

  10. Probing electroweak symmetry breaking at the SSC [Superconducting Super Collider]: A no-lose corollary

    International Nuclear Information System (INIS)

    Chanowitz, M.S.

    1987-01-01

    Low energy theorems are derived for scattering of longitudinally polarized W and Z's, providing the basis for an estimate of the observable signal at the SSC if electroweak symmetry breaking is due to new physics at the TeV scale

  11. Effects of translational symmetry breaking induced by the boundaries in a driven diffusive system

    DEFF Research Database (Denmark)

    Andersen, Jørgen Vitting; Leung, Kwan-tai

    1991-01-01

    We study the effects of the boundary conditions in a driven diffusive lattice-gas model which is known to display kinetic phase transitions. We find, in the case of attractive interaction, that a boundary-condition-induced symmetry breaking of the translational invariance, along the direction...

  12. Dynamical symmetry breaking of lambda- and vee-type three-level ...

    Indian Academy of Sciences (India)

    Dynamical symmetry breaking of lambda- and vee-type three-level systems on quantization of the field modes. MIHIR RANJAN NATH1, SURAJIT SEN1, ASOKE KUMAR SEN2 and. GAUTAM GANGOPADHYAY3,∗. 1Department of Physics, Guru Charan College, Silchar 788 004, India. 2Department of Physics, Assam ...

  13. Explaining the symmetry breaking observed in the endofullerenes H2@C60, HF@C60, and H2O@C60.

    Science.gov (United States)

    Felker, Peter M; Vlček, Vojtěch; Hietanen, Isaac; FitzGerald, Stephen; Neuhauser, Daniel; Bačić, Zlatko

    2017-11-29

    Symmetry breaking has been recently observed in the endofullerenes M@C 60 (M = H 2 , HF, H 2 O), manifesting in the splittings of the three-fold degenerate ground states of the endohedral ortho-H 2 , ortho-H 2 O and the j = 1 level of HF. The nature of the interaction causing the symmetry breaking is established in this study. A fragment of the solid C 60 is considered, comprised of the central C 60 molecule surrounded by twelve nearest-neighbor (NN) C 60 molecules. The fullerenes have either P (major) or H (minor) orientational orderings, and are assumed to be rigid with I h symmetry. Only the central C 60 is occupied by the guest molecule M, while the NN fullerenes are all empty. The key proposition of the study is that the electrostatic interactions between the charge densities on the NN C 60 molecules and that on M inside the central C 60 give rise to the symmetry breaking responsible for the measured level splittings. Using this model, the M@C 60 level splittings of interest are calculated variationally and using perturbation theory, for both the P and H orientations. Those obtained for the dominant P orientation are in excellent agreement with the experimental results, with respect to the splitting magnitudes and patterns, for all three M@C 60 systems considered, pointing strongly to the quadrupolar M-NN interactions as the main cause of the symmetry breaking. The level splittings calculated for the H orientation are about 30 times smaller than the ones in the P orientation.

  14. Symmetry-Breaking Charge Transfer in a Zinc Chlorodipyrrin Acceptor for High Open Circuit Voltage Organic Photovoltaics

    KAUST Repository

    Bartynski, Andrew N.

    2015-04-29

    © 2015 American Chemical Society. Low open-circuit voltages significantly limit the power conversion efficiency of organic photovoltaic devices. Typical strategies to enhance the open-circuit voltage involve tuning the HOMO and LUMO positions of the donor (D) and acceptor (A), respectively, to increase the interfacial energy gap or to tailor the donor or acceptor structure at the D/A interface. Here, we present an alternative approach to improve the open-circuit voltage through the use of a zinc chlorodipyrrin, ZCl [bis(dodecachloro-5-mesityldipyrrinato)zinc], as an acceptor, which undergoes symmetry-breaking charge transfer (CT) at the donor/acceptor interface. DBP/ZCl cells exhibit open-circuit voltages of 1.33 V compared to 0.88 V for analogous tetraphenyldibenzoperyflanthrene (DBP)/C60-based devices. Charge transfer state energies measured by Fourier-transform photocurrent spectroscopy and electroluminescence show that C60 forms a CT state of 1.45 ± 0.05 eV in a DBP/C60-based organic photovoltaic device, while ZCl as acceptor gives a CT state energy of 1.70 ± 0.05 eV in the corresponding device structure. In the ZCl device this results in an energetic loss between ECT and qVOC of 0.37 eV, substantially less than the 0.6 eV typically observed for organic systems and equal to the recombination losses seen in high-efficiency Si and GaAs devices. The substantial increase in open-circuit voltage and reduction in recombination losses for devices utilizing ZCl demonstrate the great promise of symmetry-breaking charge transfer in organic photovoltaic devices.

  15. Time-translation-symmetry breaking in a driven oscillator: From the quantum coherent to the incoherent regime

    Science.gov (United States)

    Zhang, Yaxing; Gosner, J.; Girvin, S. M.; Ankerhold, J.; Dykman, M. I.

    2017-11-01

    We study the breaking of the discrete time-translation symmetry in small periodically driven quantum systems. These systems are intermediate between large closed systems and small dissipative systems, which both display such symmetry breaking but have qualitatively different dynamics. As a nontrivial example, strongly different from the familiar case of parametric resonance, we consider period tripling in a quantum nonlinear oscillator. We develop theoretical methods of the analysis of period tripling, including the theory of multiple-state resonant tunneling in phase space with the account taken of the involved geometric phase. For moderately strong driving, the period tripling persists for a time, which is exponentially long compared with all dynamical times. This time is further extended by an even weak decoherence.

  16. Antiferroquadrupolar Order and Rotational Symmetry Breaking in a Generalized Bilinear-Biquadratic Model on a Square Lattice

    Science.gov (United States)

    Lai, Hsin-Hua; Hu, Wen-Jun; Nica, Emilian M.; Yu, Rong; Si, Qimiao

    2017-04-01

    The magnetic and nematic properties of the iron chalcogenides have recently been the subject of intense interest. Motivated by the proposed antiferroquadrupolar and Ising-nematic orders for the bulk FeSe, we study the phase diagram of an S =1 generalized bilinear-biquadratic model with multineighbor interactions. We find a large parameter regime for a (π , 0) antiferroquadrupolar phase, showing how quantum fluctuations stabilize it by lifting an infinite degeneracy of certain semiclassical states. Evidence for this C4 -symmetry-breaking quadrupolar phase is also provided by an unbiased density matrix renormalization group analysis. We discuss the implications of our results for FeSe and related iron-based superconductors.

  17. Symmetry breaking by electric discharges in water and formation of light magnetic monopoles in an extended standard model. Pt. I

    Energy Technology Data Exchange (ETDEWEB)

    Stumpf, Harald [Tuebingen Univ. (Germany). Inst. of Theoretical Physics

    2011-03-15

    By Lochak (theory) and Urutskoev (experiment) the hypothesis has been suggested that during electric discharges in water (fluids) light magnetic monopoles can be created which according to Lochak should be considered as a kind of excited neutrinos. Based on a quantum field theoretic development of de Broglie's and Heisenberg's fusion ideas and the results of preceding papers a transparent proof is given that such magnetic monopoles can occur during discharges. In the theoretical description these circumstances are formulated within the scope of an extended (effective) Standard Model and the monopoles with vanishing electric charge arise from neutrinos whose states are modified by the symmetry breaking caused by the discharge. In the introduction some technical implications are referred to. The article is divided into two parts. (orig.)

  18. Symmetry breaking in clogging for oppositely driven particles

    Science.gov (United States)

    Glanz, Tobias; Wittkowski, Raphael; Löwen, Hartmut

    2016-11-01

    The clogging behavior of a symmetric binary mixture of colloidal particles that are driven in opposite directions through constrictions is explored by Brownian dynamics simulations and theory. A dynamical state with a spontaneously broken symmetry occurs where one species is flowing and the other is blocked for a long time, which can be tailored by the size of the constrictions. Moreover, we find self-organized oscillations in clogging and unclogging of the two species. Apart from statistical physics, our results are of relevance for fields like biology, chemistry, and crowd management, where ions, microparticles, pedestrians, or other particles are driven in opposite directions through constrictions.

  19. Baryon spectroscopy: symmetries, symmetry breaking and hadronic loops

    International Nuclear Information System (INIS)

    Zenczykowski, P.

    1985-01-01

    The problem of hadronic loop effects in baryon spectroscopy is thoroughly discussed. It is argued that such effects very likely constitute the dominant contribution to the observed splitting and mixing pattern of the (56,0 + ) and (70,1 - ) baryon multiplets. In particular, this dominance is demonstrated in the original Isgur-Karl-Koniuk model of baryons, in which hadronic loops are shown to provide an explanation for at least 2/3 of the observed size of splittings, both for the ground-state and excited baryons. The unitarity-induced mixing angles in the (70,1 - )-multiplet are also shown to be in good agreement with experiment. For the ground-state baryons the formula relating Σ-Λ and Δ-Ν mass differences - as originally derived by de Rujula, Georgi and Glashow from the single gluon exchange-is obtained from the hadronic loop effects as well. This (and other) results are derived after taking into account a complete set of symmetry-related hadronic loops. Consideration of such a complete set of symmetry-related processes is shown to be crucial in restoring proper symmetry properties of the calculated spectrum. 74 refs., 10 figs., 4 tabs. (author)

  20. Dynamical chiral symmetry breaking and Bethe-Salpeter equation

    Energy Technology Data Exchange (ETDEWEB)

    Naito, Kenichi [Tokyo Inst. of Tech. (Japan)

    1998-08-01

    {pi} meson, (pseudo) Nambu-Goldstone particle caused by a spontaneous breaking of chiral symmetry, was studied by use of Bethe-Salpeter (BS) equation in the limits of effective model as a bound state of quark and antiquark. The effective model has nonlocal interaction and proved to satisfy the Gell-Mann-Oaks-Renner (GMOR) mass formula by treating correct Noether current in spite of loss of local chiral invariance of interaction term. GMOR mass formula: M{sub {pi}}{sup 2}f{sub {pi}}{sup 2}{approx_equal}-2m{sub 0} was realized as the result of the dynamical breaking and the clear breaking of chiral symmetry. M{sub {pi}}, f{sub {pi}}, m{sub 0}, and indicate mass of pseudo scalar meson, decay constant, mass of quark and vacuum condensation of quark and antiquark. (S.Y.)

  1. Electro symmetry breaking and beyond the standard model

    International Nuclear Information System (INIS)

    Barklow, T.; Dawson, S.; Haber, H.E.

    1995-05-01

    The development of the Standard Model of particle physics is a remarkable success story. Its many facets have been tested at present day accelerators; no significant unambiguous deviations have yet been found. In some cases, the model has been verified at an accuracy of better than one part in a thousand. This state of affairs presents our field with a challenge. Where do we go from here? What is our vision for future developments in particle physics? Are particle physicists' recent successes a signal of the field's impending demise, or do real long-term prospects exist for further progress? We assert that the long-term health and intellectual vitality of particle physics depends crucially on the development of a new generation of particle colliders that push the energy frontier by an order of magnitude beyond present capabilities. In this report, we address the scientific issues underlying this assertion

  2. Learning about the strongly interacting symmetry breaking sector at LHC

    CERN Document Server

    Dobado, A; Peláez, J R; Ruiz, E; Urdiales, M T; Dobado, A; Herrero, M J; Pelaez, J R; Ruiz, E; Urdiales, M T

    1995-01-01

    In the present work we study the predictions for WZ and ZZ production at LHC with the Electroweak Chiral Lagrangian (EChL) approach. Our analysis will be focused on the less favored case from the experimental point of view, in which the predictions for the gauge bosons scattering amplitudes are considered in the low energy range where, by construction of the low energy approach, they reveal no resonant behavior. The study includes the complete set of amplitudes for all the polarization states of the initial and/or final gauge bosons and makes no use of the Equivalence Theorem. We express the results in terms of the range of values of the chiral parameters that will be accessible at LHC.

  3. Unitarity in gauge symmetry breaking on an orbifold

    CERN Document Server

    Abe, Y; Higashide, Y; Kobayashi, K; Matsunaga, M

    2003-01-01

    We study the unitarity bounds of scattering amplitudes in extra-dimensional gauge theory, in which the gauge symmetry is broken by the boundary conditions. The evaluation of the amplitude of the diagram including four massive gauge bosons in the external lines shows that the asymptotic power behavior of the amplitude is canceled. The calculation is carried out with the 5-dimensional standard model and the SU(5) grand unified theory, whose 5th dimensional coordinate is compactified on S sup 1 /Z sub 2. The gauge theories broken through the orbifolding preserve unitarity a high energies, similarly to the broken gauge theories in which the gauge bosons acquire masses through the Higgs mechanism. We show that the contributions of the Kaluza-Klein states play a crucial role in conserving the unitarity. (author)

  4. Electro symmetry breaking and beyond the standard model

    Energy Technology Data Exchange (ETDEWEB)

    Barklow, T. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Dawson, S. [Brookhaven National Lab., Upton, NY (United States); Haber, H.E. [California Univ., Santa Cruz, CA (United States). Inst. for Particle Physics; Siegrist, J. [Lawrence Berkeley Lab., CA (United States)

    1995-05-01

    The development of the Standard Model of particle physics is a remarkable success story. Its many facets have been tested at present day accelerators; no significant unambiguous deviations have yet been found. In some cases, the model has been verified at an accuracy of better than one part in a thousand. This state of affairs presents our field with a challenge. Where do we go from here? What is our vision for future developments in particle physics? Are particle physicists` recent successes a signal of the field`s impending demise, or do real long-term prospects exist for further progress? We assert that the long-term health and intellectual vitality of particle physics depends crucially on the development of a new generation of particle colliders that push the energy frontier by an order of magnitude beyond present capabilities. In this report, we address the scientific issues underlying this assertion.

  5. Quasiaverages, symmetry breaking and irreducible Green functions method

    Directory of Open Access Journals (Sweden)

    A.L.Kuzemsky

    2010-01-01

    Full Text Available The development and applications of the method of quasiaverages to quantum statistical physics and to quantum solid state theory and, in particular, to quantum theory of magnetism, were considered. It was shown that the role of symmetry (and the breaking of symmetries in combination with the degeneracy of the system was reanalyzed and essentially clarified within the framework of the method of quasiaverages. The problem of finding the ferromagnetic, antiferromagnetic and superconducting "symmetry broken" solutions of the correlated lattice fermion models was discussed within the irreducible Green functions method. A unified scheme for the construction of generalized mean fields (elastic scattering corrections and self-energy (inelastic scattering in terms of the equations of motion and Dyson equation was generalized in order to include the "source fields". This approach complements previous studies of microscopic theory of antiferromagnetism and clarifies the concepts of Neel sublattices for localized and itinerant antiferromagnetism and "spin-aligning fields" of correlated lattice fermions.

  6. Electroweak symmetry breaking and precision tests with a fifth dimension

    Energy Technology Data Exchange (ETDEWEB)

    Panico, Giuliano [ISAS-SISSA and INFN, Via Beirut 2-4, I-34013 Trieste (Italy); Serone, Marco [ISAS-SISSA and INFN, Via Beirut 2-4, I-34013 Trieste (Italy); Wulzer, Andrea [IFAE, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)]. E-mail: wulzer@ifae.es

    2007-01-29

    We perform a complete study of flavor and CP conserving electroweak observables in a slight refinement of a recently proposed five-dimensional model on R{sup 4}xS{sup 1}/Z{sub 2}, where the Higgs is the internal component of a gauge field and the Lorentz symmetry is broken in the fifth dimension. Interestingly enough, the relevant corrections to the electroweak observables turn out to be of universal type and essentially depend only on the value of the Higgs mass and on the scale of new physics, in our case the compactification scale 1/R. The model passes all constraints for 1/R>=4.7 TeV at 90% C.L., with a moderate fine-tuning in the parameters. The Higgs mass turns out to be always smaller than 200 GeV although higher values would be allowed, due to a large correction to the T parameter. The lightest non-SM states in the model are typically colored fermions with a mass of order 1-2 TeV.

  7. Singlet Ground State Magnetism: III Magnetic Excitons in Antiferromagnetic TbP

    DEFF Research Database (Denmark)

    Knorr, K.; Loidl, A.; Kjems, Jørgen

    1981-01-01

    The dispersion of the lowest magnetic excitations of the singlet ground state system TbP has been studied in the antiferromagnetic phase by inelastic neutron scattering. The magnetic exchange interaction and the magnetic and the rhombohedral molecular fields have been determined....

  8. Soluble and stable heptazethrenebis(dicarboximide) with a singlet open-shell ground state

    KAUST Repository

    Sun, Zhe

    2011-08-10

    A soluble and stable heptazethrene derivative was synthesized and characterized for the first time. This molecule exhibits a singlet biradical character in the ground state, which is the first case among zethrene homologue series. Exceptional stability of this heptazethrenebis(dicarboximide) raises the likelihood of its practical applications in materials science. © 2011 American Chemical Society.

  9. Introduction to the workshop: Electroweak symmetry breaking at the TeV scale

    International Nuclear Information System (INIS)

    Gaillard, M.K.

    1984-01-01

    As viewed from today's perspective, electroweak symmetry breaking is both the central issue to be addressed by physics in the TeV region, and the most compelling argument for the need to explore that region. While the picture may change considerably over the next decade, it seems reasonable to focus theoretical attention on this issue which is in fact very broad in terms of its possible ramifications. Such a concerted effort can help to sharpen the scientific case for the SSC and provide fresh theoretical input to the ongoing series of workshops and studies aimed at forming a consensus on a choice of SSC design parameters. To set the mood of the workshop the author reviews briefly the physics to be explored prior to the SSC as well as the motivations for exploration of the TeV region for hard collisions. He follows with an example of a possible scenario for the first manifestation of electroweak symmetry breaking at the SSC

  10. Asymmetric cell division in plants: mechanisms of symmetry breaking and cell fate determination.

    Science.gov (United States)

    Pillitteri, Lynn Jo; Guo, Xiaoyu; Dong, Juan

    2016-11-01

    Asymmetric cell division is a fundamental mechanism that generates cell diversity while maintaining self-renewing stem cell populations in multicellular organisms. Both intrinsic and extrinsic mechanisms underpin symmetry breaking and differential daughter cell fate determination in animals and plants. The emerging picture suggests that plants deal with the problem of symmetry breaking using unique cell polarity proteins, mobile transcription factors, and cell wall components to influence asymmetric divisions and cell fate. There is a clear role for altered auxin distribution and signaling in distinguishing two daughter cells and an emerging role for epigenetic modifications through chromatin remodelers and DNA methylation in plant cell differentiation. The importance of asymmetric cell division in determining final plant form provides the impetus for its study in the areas of both basic and applied science.

  11. Symmetry breaking and generational mixing in top-color-assisted technicolor

    International Nuclear Information System (INIS)

    Lane, K.

    1996-01-01

    Top-color-assisted technicolor provides a dynanamical explanation for electroweak and flavor symmetry breaking and for the large mass of the top quark without unnatural fine-tuning. A major challenge is to generate the observed mixing between heavy and light generations while breaking the strong top-color interactions near 1 TeV. I argue that these phenomena, as well as electroweak symmetry breaking, are intimately connected and I present a scenario for them based on nontrivial patterns of technifermion condensation. I also exhibit a class of models realizing this scenario. This picture leads to a rich phenomenology, especially in hadron and lepton collider experiments in the few hundred GeV to few TeV region and in precision electroweak tests at the Z 0 , atomic parity violation, and polarized Mo/ller scattering. copyright 1996 The American Physical Society

  12. Nonlinearity in cytoplasm viscosity can generate an essential symmetry breaking in cellular behaviors.

    Science.gov (United States)

    Tachikawa, Masashi; Mochizuki, Atsushi

    2015-01-07

    The cytoplasms of ameboid cells are nonlinearly viscous. The cell controls this viscosity by modulating the amount, localization and interactions of bio-polymers. Here we investigated how the nonlinearity infers the cellular behaviors and whether nonlinearity-specific behaviors exist. We modeled the developed plasmodium of the slime mold Physarum polycephalum as a network of branching tubes and examined the linear and nonlinear viscous cytoplasm flows in the tubes. We found that the nonlinearity in the cytoplasm׳s viscosity induces a novel type of symmetry breaking in the protoplasmic flow. We also show that symmetry breaking can play an important role in adaptive behaviors, namely, connection of behavioral modes implemented on different time scales and transportation of molecular signals from the front to the rear of the cell during cellular locomotion. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. More on cosmological constraints on spontaneous R-symmetry breaking models

    International Nuclear Information System (INIS)

    Hamada, Yuta; Kobayashi, Tatsuo; Kamada, Kohei; Ecole Polytechnique Federale de Lausanne; Ookouchi, Yutaka

    2013-10-01

    We study the spontaneous R-symmetry breaking model and investigate the cosmological constraints on this model due to the pseudo Nambu-Goldstone boson, R-axion. We consider the R-axion which has relatively heavy mass in order to complement our previous work. In this regime, model parameters, R-axions mass and R-symmetry breaking scale, are constrained by Big Bang Nucleosynthesis and overproduction of the gravitino produced from R-axion decay and thermal plasma. We find that the allowed parameter space is very small for high reheating temperature. For low reheating temperature, the U(1) R breaking scale f a is constrained as f a 12-14 GeV regardless of the value of R-axion mass.

  14. Local symmetry breaking and spin–phonon coupling in SmCrO{sub 3} orthochromite

    Energy Technology Data Exchange (ETDEWEB)

    El Amrani, M. [GREMAN CNRS UMR 7347, Université F. Rabelais, IUT de Blois, 15 rue de la Chocolatrie 41029 Blois cedex (France); Zaghrioui, M., E-mail: zaghrioui@univ-tours.fr [GREMAN CNRS UMR 7347, Université F. Rabelais, IUT de Blois, 15 rue de la Chocolatrie 41029 Blois cedex (France); Ta Phuoc, V.; Gervais, F. [GREMAN CNRS UMR 7347, Université F. Rabelais, IUT de Blois, 15 rue de la Chocolatrie 41029 Blois cedex (France); Massa, Néstor E. [Laboratorio Nacional de Investigacion y Servicios en Espectroscopia Optica-Centro CEQUINOR, Universidad Nacional de La Plata, C. C. 962, 1900 La Plata (Argentina)

    2014-06-01

    Raman scattering and infrared reflectivity performed on polycrystalline SmCrO{sub 3} support strong influence of the antiferromagnetic order on phonon modes. Both measurements show softening of some modes below T{sub N}. Such a behavior is explained by spin–phonon coupling in this compound. Furthermore, temperature dependence of the infrared spectra has demonstrated important changes compared to the Raman spectra, suggesting strong structural modifications due to the cation displacements rather to those of the oxygen ions. Our results reveal that polar distortions originating in local symmetry breaking, i.e. local non-centrosymmetry, resulting in Cr off-centring. - Highlights: • We investigated Raman and infrared phonon modes of SmCrO{sub 3} versus temperature. • Results reveal strong influence of the antiferromagnetic order on phonon modes. • Temperature dependence of the infrared spectra shows strong structural modifications suggesting local symmetry breaking.

  15. Spontaneous Symmetry Breaking and Nambu–Goldstone Bosons in Quantum Many-Body Systems

    Directory of Open Access Journals (Sweden)

    Tomáš Brauner

    2010-04-01

    Full Text Available Spontaneous symmetry breaking is a general principle that constitutes the underlying concept of a vast number of physical phenomena ranging from ferromagnetism and superconductivity in condensed matter physics to the Higgs mechanism in the standard model of elementary particles. I focus on manifestations of spontaneously broken symmetries in systems that are not Lorentz invariant, which include both nonrelativistic systems as well as relativistic systems at nonzero density, providing a self-contained review of the properties of spontaneously broken symmetries specific to such theories. Topics covered include: (i Introduction to the mathematics of spontaneous symmetry breaking and the Goldstone theorem. (ii Minimization of Higgs-type potentials for higher-dimensional representations. (iii Counting rules for Nambu–Goldstone bosons and their dispersion relations. (iv Construction of effective Lagrangians. Specific examples in both relativistic and nonrelativistic physics are worked out in detail.

  16. Magnetism and local symmetry breaking in a Mott insulator with strong spin orbit interactions.

    Science.gov (United States)

    Lu, L; Song, M; Liu, W; Reyes, A P; Kuhns, P; Lee, H O; Fisher, I R; Mitrović, V F

    2017-02-09

    Study of the combined effects of strong electronic correlations with spin-orbit coupling (SOC) represents a central issue in quantum materials research. Predicting emergent properties represents a huge theoretical problem since the presence of SOC implies that the spin is not a good quantum number. Existing theories propose the emergence of a multitude of exotic quantum phases, distinguishable by either local point symmetry breaking or local spin expectation values, even in materials with simple cubic crystal structure such as Ba 2 NaOsO 6 . Experimental tests of these theories by local probes are highly sought for. Our local measurements designed to concurrently probe spin and orbital/lattice degrees of freedom of Ba 2 NaOsO 6 provide such tests. Here we show that a canted ferromagnetic phase which is preceded by local point symmetry breaking is stabilized at low temperatures, as predicted by quantum theories involving multipolar spin interactions.

  17. Ten dimensional SO(10) G.U.T. models with dynamical symmetry breaking

    International Nuclear Information System (INIS)

    Hanlon, B.E.; Joshi, G.C.

    1993-01-01

    To date, considerations on SO (10) models within Coset Space Dimensional Reduction (CSDR) have been diagonalized to the standard model or rely upon imaginative applications of Wilson lines so as to avoid the problem of the nonexistence of an intermediate Higgs mechanism. However, there is an alternative approach involving four fermion condensates, breaking symmetries by a dynamical mechanism. Indeed, dynamical symmetry breaking has been the direction taken in some SU(5) models within this framework in order to avoid the problems of electroweak symmetry breaking at the compactification scale. This paper presents realistic models which utilize this mechanism. It is shown that the appropriate fermionic representations can emerge from CSDR and the construction of such condensates within the constraints of this scheme is presented. By introducing discrete symmetries onto the internal manifold a strong breaking of the SO(10) G.U.T. is produced and, more importantly, eliminate Higgs fields of geometrical origin. 31 refs

  18. PT symmetry breaking in non-central potentials

    International Nuclear Information System (INIS)

    Levai, G.

    2007-01-01

    Complete text of publication follows. PT-symmetric systems represent a special example for non-hermitian problems in quantum mechanics. The Hamiltonian of these systems is invariant under the simultaneous action of the P space and T time inversion operations. They resemble hermitian problems in that they typically possess real energy spectrum. However, increasing non-hermiticity, e.g. the imaginary potential component the real energy eigenvalues merge pairwise and turn into complex conjugate pairs and at the same time, the energy eigenstates cease to be eigenstates of the PT operator. The mechanism of this spontaneous breakdown of PT symmetry has been investigated in one spatial dimension, and our aim was to extend these studies to higher dimensions. Assuming that the solutions of the Schroedinger equation -Δψ(r) + V (r)ψ(r) = Eψ(r) can be obtained by the separation of the radial and angular variables, we substitute ψ(r,θ,φ) = r -1 φ(r) sin -1/2 ω(θ)τ(ψ) in (4), where r [0,∞), θ [0,π] and ψ [0,2π]. Further, we assume that the angular components of the wave function satisfy ω' = (P(θ) - p)ω, τ' = (K(ψ) - k)τ, where τ(ψ) has to be defined with periodic boundary conditions. Then the complete three-dimensional problem becomes solvable if the non-central potential takes the form V(r,θ,ψ) = V 0 (r)+ K(ψ)/r 2 sin 2 θ + P(θ)/r 2 - k-1/4/r 2 sin 2 θ. Here V 0 (r) is a central potential appearing in -φ'+[V 0 (r) + 1/r 2 (p - 1/4] φ - Eφ = 0. Note that is formally identical with a conventional radial Schroedinger equation complete with a centrifugal term. In order to solve properly, the state dependence of has to be eliminated, i.e. its dependence on k has to be cancelled by combining the last two terms. This effectively means that has to be solved with a potential P(θ) that contains a sin -2 θ type term. Next we investigate under which conditions the non-central potential exhibits PT symmetry. It is seen that space reflection P : r → -r

  19. Photophysics of trioxatriangulenium ion. Electrophilic reactivity in the ground state and excited singlet state

    DEFF Research Database (Denmark)

    Reynisson, J.; Wilbrandt, R.; Brinck, V.

    2002-01-01

    . The physical and chemical properties of the excited singlet state of the trioxatriangulenium (TOTA(+)) carbenium ion are investigated by experimental and Computational means. The degeneracy of the lowest excited states is counteracted by Jahn-Teller-type distortion, which leads to vibronic broadening...... of the long wavelength absorption band. A strong fluorescence is observed at 520 nm (tau(n) = 14.6 ns, phi(n) = 0.12 in deaerated acetonitrile). The fluorescence is quenched by 10 aromatic electron donors predominantly via a dynamic charge transfer mechanism, but ground state complexation is shown...... triphenylenes is studied separately. Phosphorescence spectra, triplet lifetimes, and triplet-triplet absorption spectra are provided. In the discussion, TOTA(+) is compared to the unsubstituted xanthenium ion and its 9-phenyl derivative with respect to the excited state properties....

  20. Cosmological baryon number domain structure from symmetry-breaking in grand unified field theories

    Science.gov (United States)

    Brown, R. W.; Stecker, F. W.

    1979-01-01

    It is suggested that grand unified field theories with spontaneous symmetry breaking in the very early big-bang can lead more naturally to a baryon symmetric cosmology with a domain structure than to a totally baryon asymmetric cosmology. The symmetry is broken in a randomized manner in causally independent domains, favoring neither a baryon nor an antibaryon excess on a universal scale. Arguments in favor of this cosmology and observational tests are discussed.

  1. Cosmological baryon-number domain structure from symmetry breaking in grand unified field theories

    Science.gov (United States)

    Brown, R. W.; Stecker, F. W.

    1979-01-01

    It is suggested that grand unified field theories with spontaneous symmetry breaking in the very early big bang can lead more naturally to a baryon-symmetric cosmology with a domain structure than to a totally baryon-asymmetric cosmology. The symmetry is broken in a randomized manner in causally independent domains, favoring neither a baryon nor an antibaryon excess on a universal scale. Arguments in favor of this cosmology and observational tests are discussed.

  2. Parity symmetry-breaking phase transition in a nonlinear Rabi-Hubbard lattice

    OpenAIRE

    Pyykkönen, A. (Ari)

    2015-01-01

    Abstract Lattices consisting of cavity QED and circuit QED elements have come under focus as a platform for studying several novel quantum phenomena. In particular, a lattice of Rabi systems described by the Rabi-Hubbard model is expected to display a new Z2 parity symmetry-breaking phase transition of light between a Rabi insulator and a delocalized superradiant phase. In this thesis, we examine a superconducting circuit c...

  3. Mirror symmetry breaking in cubic phases and isotropic liquids driven by hydrogen bonding.

    Science.gov (United States)

    Alaasar, Mohamed; Poppe, Silvio; Dong, Qingshu; Liu, Feng; Tschierske, Carsten

    2016-11-24

    Achiral supramolecular hydrogen bonded complexes between rod-like 4-(4-alkoxyphenylazo)pyridines and a taper shaped 4-substituted benzoic acid form achiral (Ia3[combining macron]d) and chiral "Im3[combining macron]m-type" bicontinuous cubic (I432) phases and a chiral isotropic liquid mesophase (Iso 1 [ * ] ). The chiral phases, resulting from spontaneous mirror symmetry breaking, represent conglomerates of macroscopic chiral domains eventually leading to uniform chirality.

  4. Chiral-symmetry breaking in two-dimensional SU(2) QCD with fermions

    International Nuclear Information System (INIS)

    Min, J.; Kao, C.; Chen, Y.

    1991-01-01

    We study chiral symmetry of SU(2) Yang-Mills theory coupled to an unflavored fermion on a two-dimensional lattice using a hybrid algorithm based on the projector Hamiltonian Monte Carlo method. The correlation functions of a chiral condensate and of fermion occupation number are calculated. We find chiral-symmetry breaking in the continuum limit. The theory is calculated to reside in only one phase in which chiral symmetry is broken

  5. Spontaneous symmetry breaking, quantization of the electric charge and the anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, Afsar (Manchester Univ. (United Kingdom). Dept. of Theoretical Physics)

    1990-09-01

    Cancellation of anomalies and on ensuring that fermions are massive, one obtains quantization of the electric charge, which is shown to be independent of the hypercharge quantum number of the Higgs doublet in the Standard Model. Ignorance of this fact can lead to pitfalls. It is shown that contrary to the popular belief, charge quantization is not a consequence of the anomalies but that in addition spontaneous symmetry breaking is essential. (author).

  6. 300 nm bandwidth adiabatic SOI polarization splitter-rotators exploiting continuous symmetry breaking.

    Science.gov (United States)

    Socci, Luciano; Sorianello, Vito; Romagnoli, Marco

    2015-07-27

    Adiabatic polarization splitter-rotators are investigated exploiting continuous symmetry breaking thereby achieving significant device size and losses reduction in a single mask fabrication process for both SOI channel and ridge waveguides. A crosstalk lower than -25 dB is expected over 300nm bandwidth, making the device suitable for full grid CWDM and diplexer/triplexer FTTH applications at 1310, 1490 and 1550nm.

  7. QCD diffraction: a critical phenomenon reflecting both confinement and chiral-symmetry breaking

    International Nuclear Information System (INIS)

    White, A.R.

    1982-07-01

    Arguments are presented for studying soft diffractive physics at anti p-p colliders in terms of Critical Pomeron Reggeon Field Theory. It is emphasized that both confinement and chiral-symmetry breaking play a vital role in the occurrence of the Critical Pomeron in QCD. SU(3) is the unique strong-interaction gauge group giving the Critical Pomeron and the maximum number of quarks allowed by asymptotic freedom is required for criticality

  8. Recent progress for Linear Collider SM/BSM Higgs/electroweak symmetry breaking calculations

    International Nuclear Information System (INIS)

    Reuter, Juergen

    2012-01-01

    In this paper I review the calculations (and partially simulations and theoretical studies) that have been made and published during the last two to three years focusing on the electroweak symmetry breaking sector and the Higgs boson(s) within the Standard Model and models beyond the Standard Model (BSM) at or relevant for either the International Linear Collider (ILC) or the Compact Linear Collider (CLIC), commonly abbreviated as Linear Collider (LC). (orig.)

  9. Experimental verification of orbital engineering at the atomic scale: Charge transfer and symmetry breaking in nickelate heterostructures

    Science.gov (United States)

    Phillips, Patrick J.; Rui, Xue; Georgescu, Alexandru B.; Disa, Ankit S.; Longo, Paolo; Okunishi, Eiji; Walker, Fred; Ahn, Charles H.; Ismail-Beigi, Sohrab; Klie, Robert F.

    2017-05-01

    Epitaxial strain, layer confinement, and inversion symmetry breaking have emerged as powerful new approaches to control the electronic and atomic-scale structural properties of complex metal oxides. Trivalent rare-earth (RE) nickelate R E NiO3 heterostructures have been shown to be exemplars since the orbital occupancy, degeneracy, and, consequently, electronic/magnetic properties can be altered as a function of epitaxial strain, layer thickness, and superlattice structure. One recent example is the tricomponent LaTiO3-LaNiO3-LaAlO3 superlattice which exhibits charge transfer and orbital polarization as the result of its interfacial dipole electric field. A crucial step towards control of these parameters for future electronic and magnetic device applications is to develop an understanding of both the magnitude and range of the octahedral network's response towards interfacial strain and electric fields. An approach that provides atomic-scale resolution and sensitivity towards the local octahedral distortions and orbital occupancy is therefore required. Here, we employ atomic-resolution imaging coupled with electron spectroscopies and first-principles theory to examine the role of interfacial charge transfer and symmetry breaking in a tricomponent nickelate superlattice system. We find that nearly complete charge transfer occurs between the LaTiO3 and LaNiO3 layers, resulting in a mixed Ni2 +/Ni3 + valence state. We further demonstrate that this charge transfer is highly localized with a range of about 1 unit cell within the LaNiO3 layers. We also show how Wannier-function-based electron counting provides a simple physical picture of the electron distribution that connects directly with formal valence charges. The results presented here provide important feedback to synthesis efforts aimed at stabilizing new electronic phases that are not accessible by conventional bulk or epitaxial film approaches.

  10. Symmetry associated with symmetry break: Revisiting ants and humans escaping from multiple-exit rooms

    Science.gov (United States)

    Ji, Q.; Xin, C.; Tang, S. X.; Huang, J. P.

    2018-02-01

    Crowd panic has incurred massive injuries or deaths throughout the world, and thus understanding it is particularly important. It is now a common knowledge that crowd panic induces "symmetry break" in which some exits are jammed while others are underutilized. Amazingly, here we show, by experiment, simulation and theory, that a class of symmetry patterns come to appear for ants and humans escaping from multiple-exit rooms while the symmetry break exists. Our symmetry pattern is described by the fact that the ratio between the ensemble-averaging numbers of ants or humans escaping from different exits is equal to the ratio between the widths of the exits. The mechanism lies in the effect of heterogeneous preferences of agents with limited information for achieving the Nash equilibrium. This work offers new insights into how to improve public safety because large public areas are always equipped with multiple exits, and it also brings an ensemble-averaging method for seeking symmetry associated with symmetry breaking.

  11. Dynamical mechanism of symmetry breaking and particle mass generation in gauge field theories

    International Nuclear Information System (INIS)

    Miranskij, V.A.; Fomin, P.I.

    1985-01-01

    The dynamics of the spotaneous symmetry breaking and the particle mass generation in gauge theories with no fundamental scalar fields is considered. The emphasis is on the consideration of the symmetry breaking mechanism connected with the dynamics of the supercritical Coulomb-like forces caused by the gauge boson exchange between fermions. This mechanism is applied to different gauge theories, in particular, to the description of the spontaneous chira symmetry breaking in quantum chromodynamics. The mass relations for pseudoscalar meson nonet are obtained and it is shown that this mechanism resuls in the dynamical realisation of the hypothesis of the partial conservation of the axial-vector currents. The qualitative description of scalar mesons is given. The nature of the ultraviolet divergencies in quantum electrodynamics (QED) is investigated from the viewpoint of the dynamics of the fermion mass generation. The mechanism of the appearance of the additional (in comparison with perturbation theory) ultraviolet divergencies in QED with large bare coupling constant is indicated. The physical phenomenon underlying this mechanism is identified as the field theory analogue of the quantum mechanical ''fall into the centre'' (collapse) phenomenon. The similr phenomenon is shown to take place in some two-dimensional quantum field models. The dynamics of the bifermion condensates formation in tumblin gauge theories is briefly discussed

  12. Spontaneous symmetry breaking in ΡΤ symmetric systems with nonlinear damping

    International Nuclear Information System (INIS)

    Karthiga, S.; Chandrasekar, V.K.; Senthilvelan, M.; Lakshmanan, M.

    2016-01-01

    In this talk, we discuss the remarkable role of position dependent damping in determining the parametric regions of symmetry breaking in nonlinear ΡΤ -symmetric systems. We illustrate the nature of ΡΤ-symmetry preservation and breaking with reference to a remarkable integrable scalar nonlinear system. In the two dimensional cases of such position dependent damped systems, we unveil the existence of a class of novel bi-ΡΤ -symmetric systems which have two fold ΡΤ symmetries. We discuss the dynamics of these systems and show how symmetry breaking occurs, that is whether the symmetry breaking of the two ΡΤ symmetries occurs in pair or occurs one by one. The addition of linear damping in these nonlinearly damped systems induces competition between the two types of damping. This competition results in a ΡΤ phase transition in which the ΡΤ symmetry is broken for lower loss/gain strength and is restored by increasing the loss/gain strength. We also show that by properly designing the form of the position dependent damping, we can tailor the ΡΤ-symmetric regions of the system. (author)

  13. Probability of color singlet chain states in e+e- annihilation

    International Nuclear Information System (INIS)

    Wang, Qun; Gustafson, Gosta; Jin, Yi; Xie, Qu-bing

    2001-01-01

    We use the method of the color effective Hamiltonian to study the structure of color singlet chain states in N c =3 and in the large N c limit. In order to obtain their total fraction when N c is finite, we illustrate how to orthogonalize these nonorthogonal states. We give numerical results for the fraction of orthogonalized states in e + e - ->q bar qgg. With the help of a diagram technique, we derive their fraction up to O(1/N c 2 ) for the general multigluon process. For large N c the singlet chain states correspond to well-defined color topologies. Therefore we may expect that the fraction of non-color-singlet-chain states is an estimate of the fraction of events where color reconnection is possible. In the case of soft gluon bremsstrahlung, we give an explicit form for the color effective Hamiltonian which leads to the dipole cascade formulation for parton showering in leading order in N c . The next-to-leading order corrections are also given for e + e - ->qbar qg 1 g 2 and e + e - ->qbar qg 1 g 2 g 3

  14. In silico reconstitution of actin-based symmetry breaking and motility.

    Directory of Open Access Journals (Sweden)

    Mark J Dayel

    2009-09-01

    Full Text Available Eukaryotic cells assemble viscoelastic networks of crosslinked actin filaments to control their shape, mechanical properties, and motility. One important class of actin network is nucleated by the Arp2/3 complex and drives both membrane protrusion at the leading edge of motile cells and intracellular motility of pathogens such as Listeria monocytogenes. These networks can be reconstituted in vitro from purified components to drive the motility of spherical micron-sized beads. An Elastic Gel model has been successful in explaining how these networks break symmetry, but how they produce directed motile force has been less clear. We have combined numerical simulations with in vitro experiments to reconstitute the behavior of these motile actin networks in silico using an Accumulative Particle-Spring (APS model that builds on the Elastic Gel model, and demonstrates simple intuitive mechanisms for both symmetry breaking and sustained motility. The APS model explains observed transitions between smooth and pulsatile motion as well as subtle variations in network architecture caused by differences in geometry and conditions. Our findings also explain sideways symmetry breaking and motility of elongated beads, and show that elastic recoil, though important for symmetry breaking and pulsatile motion, is not necessary for smooth directional motility. The APS model demonstrates how a small number of viscoelastic network parameters and construction rules suffice to recapture the complex behavior of motile actin networks. The fact that the model not only mirrors our in vitro observations, but also makes novel predictions that we confirm by experiment, suggests that the model captures much of the essence of actin-based motility in this system.

  15. Benchmarking Density Functional Theory Approaches for the Description of Symmetry-Breaking in Long Polymethine Dyes

    KAUST Repository

    Gieseking, Rebecca L.

    2016-04-25

    Long polymethines are well-known experimentally to symmetry-break, which dramatically modifies their linear and nonlinear optical properties. Computational modeling could be very useful to provide insight into the symmetry-breaking process, which is not readily available experimentally; however, accurately predicting the crossover point from symmetric to symmetry-broken structures has proven challenging. Here, we benchmark the accuracy of several DFT approaches relative to CCSD(T) geometries. In particular, we compare analogous hybrid and long-range corrected (LRC) functionals to clearly show the influence of the functional exchange term. Although both hybrid and LRC functionals can be tuned to reproduce the CCSD(T) geometries, the LRC functionals are better performing at reproducing the geometry evolution with chain length and provide a finite upper limit for the gas-phase crossover point; these methods also provide good agreement with the experimental crossover points for more complex polymethines in polar solvents. Using an approach based on LRC functionals, a reduction in the crossover length is found with increasing medium dielectric constant, which is related to localization of the excess charge on the end groups. Symmetry-breaking is associated with the appearance of an imaginary frequency of b2 symmetry involving a large change in the degree of bond-length alternation. Examination of the IR spectra show that short, isolated streptocyanines have a mode at ~1200 cm-1 involving a large change in bond-length alternation; as the polymethine length or the medium dielectric increases, the frequency of this mode decreases before becoming imaginary at the crossover point.

  16. Charge independence, charge symmetry breaking in the S-wave nucleon-nucleon interaction, and renormalization

    Energy Technology Data Exchange (ETDEWEB)

    Alvaro Calle Cordon,Manuel Pavon Valderrama,Enrique Ruiz Arriola

    2012-02-01

    We study the interplay between charge symmetry breaking and renormalization in the NN system for S-waves. We find a set of universality relations which disentangle explicitly the known long distance dynamics from low energy parameters and extend them to the Coulomb case. We analyze within such an approach the One-Boson-Exchange potential and the theoretical conditions which allow to relate the proton-neutron, proton-proton and neutron-neutron scattering observables without the introduction of extra new parameters and providing good phenomenological success.

  17. Charge symmetry breaking in pn {yields} d {pi}{sup 0}

    Energy Technology Data Exchange (ETDEWEB)

    Filin, Arseniy [Institute for Theoretical and Experimental Physics, 117218, B. Cheremushkinskaya 25, Moscow (Russian Federation); Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, D-53115 Bonn (Germany); Baru, Vadim [Institut fuer Kernphysik (Theorie), Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Institute for Theoretical and Experimental Physics, 117218, B. Cheremushkinskaya 25, Moscow (Russian Federation); Epelbaum, Evgeny [Institut fuer Kernphysik (Theorie), Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, D-53115 Bonn (Germany); Bethe Center for Theoretical Physics, Universitaet Bonn, D-53115 Bonn (Germany); Haidenbauer, Johann; Hanhart, Christoph [Institut fuer Kernphysik (Theorie), Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich (Germany); Kudryavtsev, Alexander [Institute for Theoretical and Experimental Physics, 117218, B. Cheremushkinskaya 25, Moscow (Russian Federation); Meissner, Ulf G. [Institut fuer Kernphysik (Theorie), Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, D-53115 Bonn (Germany); Bethe Center for Theoretical Physics, Universitaet Bonn, D-53115 Bonn (Germany); Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich (Germany)

    2010-07-01

    We study charge symmetry breaking (CSB) in the reaction pn {yields} d {pi}{sup 0}. CSB manifests itself in a forward-backward asymmetry of the differential cross section measured recently at TRIUMF. A complete calculation of CSB effects at leading order in chiral perturbation theory is performed. A new leading-order operator is included. This allowed us to extract the strong contribution to the neutron-proton mass difference. The value obtained is consistent with the result of Gasser and Leutwyler based on Cottingham sum rule and an extraction from lattice QCD.

  18. Symmetry breaking and uniqueness for the incompressible Navier-Stokes equations

    Science.gov (United States)

    Dascaliuc, Radu; Michalowski, Nicholas; Thomann, Enrique; Waymire, Edward C.

    2015-07-01

    The present article establishes connections between the structure of the deterministic Navier-Stokes equations and the structure of (similarity) equations that govern self-similar solutions as expected values of certain naturally associated stochastic cascades. A principle result is that explosion criteria for the stochastic cascades involved in the probabilistic representations of solutions to the respective equations coincide. While the uniqueness problem itself remains unresolved, these connections provide interesting problems and possible methods for investigating symmetry breaking and the uniqueness problem for Navier-Stokes equations. In particular, new branching Markov chains, including a dilogarithmic branching random walk on the multiplicative group (0, ∞), naturally arise as a result of this investigation.

  19. Symmetry breaking and uniqueness for the incompressible Navier-Stokes equations.

    Science.gov (United States)

    Dascaliuc, Radu; Michalowski, Nicholas; Thomann, Enrique; Waymire, Edward C

    2015-07-01

    The present article establishes connections between the structure of the deterministic Navier-Stokes equations and the structure of (similarity) equations that govern self-similar solutions as expected values of certain naturally associated stochastic cascades. A principle result is that explosion criteria for the stochastic cascades involved in the probabilistic representations of solutions to the respective equations coincide. While the uniqueness problem itself remains unresolved, these connections provide interesting problems and possible methods for investigating symmetry breaking and the uniqueness problem for Navier-Stokes equations. In particular, new branching Markov chains, including a dilogarithmic branching random walk on the multiplicative group (0, ∞), naturally arise as a result of this investigation.

  20. Symmetry breaking and uniqueness for the incompressible Navier-Stokes equations

    International Nuclear Information System (INIS)

    Dascaliuc, Radu; Thomann, Enrique; Waymire, Edward C.; Michalowski, Nicholas

    2015-01-01

    The present article establishes connections between the structure of the deterministic Navier-Stokes equations and the structure of (similarity) equations that govern self-similar solutions as expected values of certain naturally associated stochastic cascades. A principle result is that explosion criteria for the stochastic cascades involved in the probabilistic representations of solutions to the respective equations coincide. While the uniqueness problem itself remains unresolved, these connections provide interesting problems and possible methods for investigating symmetry breaking and the uniqueness problem for Navier-Stokes equations. In particular, new branching Markov chains, including a dilogarithmic branching random walk on the multiplicative group (0, ∞), naturally arise as a result of this investigation

  1. Dynamical symmetry breaking in the Jackiw-Johnson model and the gauge technique

    International Nuclear Information System (INIS)

    Singh, J.P.

    1984-01-01

    The Jackiw-Johnson model of dynamical gauge symmetry breaking has been re-examined in the light of the gauge technique. In the limit where the ratio of the axial to vector coupling constants becomes small, or, consistently, in the limit where the ratio of the axial-vector-boson mass to the fermion mass becomes small, an approximate solution for the fermion spectral function has been derived. This gives an extremely small ratio of the axial-vector-boson mass to the fermion mass. (author)

  2. Radiative symmetry breaking from flat potential in various U(1)' models

    Science.gov (United States)

    Hashimoto, Michio; Iso, Satoshi; Orikasa, Yuta

    2014-03-01

    We investigate a radiative electroweak gauge symmetry breaking scenario via the Coleman-Weinberg mechanism starting from a completely flat Higgs potential at the Planck scale ("flatland scenario"). In our previous paper, we showed that the flatland scenario is possible only when an inequality K <1 among the coefficients of the β functions is satisfied. In this paper, we calculate the number K in various models with an extra U(1) gauge sector in addition to the standard model particles. We also show the renormalization group behaviors of a couple of the models as examples.

  3. Cylindrical symmetry breaking leads to multiple filamentation generation when focusing femtosecond lasers with axicons in methanol

    Science.gov (United States)

    Gao, Hui; Sun, Xiaodong; Zeng, Bin; Xu, Shengqi; Chu, Wei; Liu, Weiwei; Cheng, Ya; Xu, Zhizhan; Mu, Guoguang

    2012-06-01

    We demonstrate that multiple filaments could be generated when focusing femtosecond laser pulses into methanol solution with an axicon. These long multiple filaments are located on the central spot and ring structures of the quasi-Bessel beam created by the axicon. Further numerical simulation reproduces the key features of the experimental observation. The outcome of simulation suggests that the cylindrical symmetry breaking in the initial beam profile could be responsible for the occurrence of multiple filamentation by using an axicon as focusing optics. Since the quasi-Bessel profile is determined by the axicon properties, the axicon has been suggested as a simple optics component to control multiple filaments.

  4. Fermion condensates and weak symmetry breaking in a superstring-based model

    International Nuclear Information System (INIS)

    Mahapatra, S.; Misra, S.P.

    1986-01-01

    We start with the gauge group SU(3)/sub C/ x SU(2)/sub L/ x U(1)/sub R/ x U(1)/sub N/ (equivalentG 3211 ), which is a rank-five subgroup of E 6 . We include chiral-fermion-condensate terms in the effective four-dimensional Lagrangian derived from superstrings and discuss how this condensation can be responsible for weak symmetry breaking at a scale of 100 GeV. One experimental effect of the above will be the nonobservation of light Higgs scalars of the Salam-Weinberg model, although the other results of the same remain unchanged

  5. Theories of Electroweak Symmetry Breaking : A Post LHC Run-I Perspective (1/3)

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    Lecture 1 : The Brout-Englert-Higgs Theory of Electroweak Symmetry Breaking The goal of this lecture is to put the discovery of the Higgs boson in historical context and qualitatively discuss the importance and meaning of its discovery. Claims that the BEH theory has its roots in the theory developments of superconductivity will be considered. Viability of the theory from several points of view will be assessed. First, has the theory been established yet as correct? Second, is the theory stable to vacuum fluctuations? And finally, is the theory natural?

  6. Observation of conformal symmetry breaking and scale invariance in expanding Fermi gases.

    Science.gov (United States)

    Elliott, E; Joseph, J A; Thomas, J E

    2014-01-31

    We precisely test scale invariance and examine local thermal equilibrium in the hydrodynamic expansion of a Fermi gas of atoms as a function of interaction strength. After release from an anisotropic optical trap, we observe that a resonantly interacting gas obeys scale-invariant hydrodynamics, where the mean square cloud size = expands ballistically (like a noninteracting gas) and the energy-averaged bulk viscosity is consistent with zero, 0.00(0.04)ℏn, with n the density. In contrast, the aspect ratios of the cloud exhibit anisotropic "elliptic" flow with an energy-dependent shear viscosity. Tuning away from resonance, we observe conformal symmetry breaking, where deviates from ballistic flow.

  7. Confinement, Chiral Symmetry Breaking and it's Restoration using Dual QCD Formalism

    Directory of Open Access Journals (Sweden)

    Punetha Garima

    2018-01-01

    Full Text Available Utilizing the dual QCD model in term of magnetic symmetry structure of non- Abelian gauge theories, the dynamical chiral-symmetry breaking using Schwinger-Dyson equation has been investigated. A close relation among the color confinement and chiralsymmetry breaking has been observed and demonstrated by computing dynamical parameters. The recovery of the chiral symmetry has also been discussed at finite temperature through the variation of quark mass function and quark condensate which gradually decreases with temperature and vanishes suddenly near the critical temperature.

  8. On the Lowest Excited Singlet State of Osmium Tetroxide.

    Science.gov (United States)

    1981-03-10

    aqreemert indicates that N, is involved in the proqression in the lower T2 state. Thee conclusions are consistent with those reached throuqh MCD studies of...Diemann, Chem. Phys. Let.. 20, 540 tI973). P~ ~~ -MIR... a 12 19. P. Day, L. Disiplo, and L. Oleari , Chem. Phys. Lett. 5, 533 (1970). 20. L.W. Johnson...E. Hughes, Jr., and S.P. McGlynn, J. Chem. Phys. 55, 4476 (1971), 21. J.C. Collingwood, P. Day, R.G. Denning, D.J. Robbins, L. Disiplo, and L. Oleari

  9. Global potential energy surface of ground state singlet spin O4

    Science.gov (United States)

    Mankodi, Tapan K.; Bhandarkar, Upendra V.; Puranik, Bhalchandra P.

    2018-02-01

    A new global potential energy for the singlet spin state O4 system is reported using CASPT2/aug-cc-pVTZ ab initio calculations. The geometries for the six-dimensional surface are constructed using a novel point generation scheme that employs randomly generated configurations based on the beta distribution. The advantage of this scheme is apparent in the reduction of the number of required geometries for a reasonably accurate potential energy surface (PES) and the consequent decrease in the overall computational effort. The reported surface matches well with the recently published singlet surface by Paukku et al. [J. Chem. Phys. 147, 034301 (2017)]. In addition to the O4 PES, the ground state N4 PES is also constructed using the point generation scheme and compared with the existing PES [Y. Paukku et al., J. Chem. Phys. 139, 044309 (2013)]. The singlet surface is constructed with the aim of studying high energy O2-O2 collisions and predicting collision induced dissociation cross section to be used in simulating non-equilibrium aerothermodynamic flows.

  10. Zethrenes, Extended p -Quinodimethanes, and Periacenes with a Singlet Biradical Ground State

    KAUST Repository

    Sun, Zhe

    2014-08-19

    ConspectusResearchers have studied polycyclic aromatic hydrocarbons (PAHs) for more than 100 years, and most PAHs in the neutral state reported so far have a closed-shell electronic configuration in the ground state. However, recent studies have revealed that specific types of polycyclic hydrocarbons (PHs) could have a singlet biradical ground state and exhibit unique electronic, optical, and magnetic activities. With the appropriate stabilization, these new compounds could prove useful as molecular materials for organic electronics, nonlinear optics, organic spintronics, organic photovoltaics, and energy storage devices. However, before researchers can use these materials to design new devices, they need better methods to synthesize these molecules and a better understanding of the fundamental relationship between the structure and biradical character of these compounds and their physical properties. Their biradical character makes these compounds difficult to synthesize. These compounds are also challenging to physically characterize and require the use of various experimental techniques and theoretic methods to comprehensively describe their unique properties.In this Account, we will discuss the chemistry and physics of three types of PHs with a significant singlet biradical character, primarily developed in our group. These structures are zethrenes, Z-shaped quinoidal hydrocarbons; hydrocarbons that include a proaromatic extended p-quinodimethane unit; and periacenes, acenes fused in a peri-Arrangement. We used a variety of synthetic methods to prepare these compounds and stabilized them using both thermodynamic and kinetic approaches. We probed their ground-state structures by electronic absorption, NMR, ESR, SQUID, Raman spectroscopy, and X-ray crystallography and also performed density functional theory calculations. We investigated the physical properties of these PHs using various experimental methods such as one-photon absorption, two-photon absorption

  11. Absence of Intramolecular Singlet Fission in Pentacene-Perylenediimide Heterodimers: The Role of Charge Transfer State.

    Science.gov (United States)

    Wang, Long; Wu, Yishi; Chen, Jianwei; Wang, Lanfen; Liu, Yanping; Yu, Zhenyi; Yao, Jiannian; Fu, Hongbing

    2017-11-16

    A new class of donor-acceptor heterodimers based on two singlet fission (SF)-active chromophores, i.e., pentacene (Pc) and perylenediimide (PDI), was developed to investigate the role of charge transfer (CT) state on the excitonic dynamics. The CT state is efficiently generated upon photoexcitation. However, the resulting CT state decays to different energy states depending on the energy levels of the CT state. It undergoes extremely rapid deactivation to the ground state in polar CH 2 Cl 2 , whereas it undergoes transformation to a Pc triplet in nonpolar toluene. The efficient triplet generation in toluene is not due to SF but CT-mediated intersystem crossing. In light of the energy landscape, it is suggested that the deep energy level of the CT state relative to that of the triplet pair state makes the CT state actually serve as a trap state that cannot undergoes an intramolecular singlet fission process. These results provide guidance for the design of SF materials and highlight the requisite for more widely applicable design principles.

  12. Infrared aspects of spontaneous symmetry breaking of gauge theories in two and three dimensions

    International Nuclear Information System (INIS)

    Cho, H.T.

    1987-01-01

    The spontaneous chiral symmetry breaking in SU(N) quantum chromodynamics (QCD) in two dimensions is investigated by calculating the order parameter , where psi is the fermion in the theory, in the authors approximation. In the chiral limit, where the mass of the fermion m → O, is found to be non-zero both in the finite N and N → infinity cases. This implies that chiral symmetry is spontaneously broken by infrared effects in all these cases. The Wilson loop expectation value is calculated for again SU(N) QCD in two dimensions, without fermions. In two dimensions, the Coulomb potential is linear, and thus confining. Under the authors approximation, the area law of the Wilson loop is indeed obtained as expected, for all values of N; in addition, the N-dependent polynomial multiplying the Wilson exponential is also obtained. In quantum electrodynamics (QED) in three dimensions there is a possibility of spontaneous breaking of parity. The authors consider this possibility by studying and the photon propagator. It is found that in the limit m → O, is zero and the photon has a zero mass pole. Therefore, there is no sign of spontaneous parity violation in (QED) in three dimensions induced by infrared effects, in contrast to the positive result of chiral symmetry breaking in two dimensions

  13. On the Possible Links Between Electroweak Symmetry Breaking and Dark Matter

    International Nuclear Information System (INIS)

    Hambye, Thomas; Tytgat, Michel H. G.

    2009-01-01

    The mechanism behind electroweak symmetry breaking (EWSB) and the nature of dark matter (DM) are currently very important issues in particle physics. Usually, in most models, these two issues are not or poorly connected. However, since a natural dark matter candidate is a weakly interacting massive particle or WIMP, with mass around the electroweak scale, it is clearly of interest to investigate the possibility that DM and EWSB are closely related. In the context of a very simple extension of the Standard Model, the Inert Doublet Model, we show that dark matter could play a crucial role in the breaking of the electroweak symmetry. In this model, dark matter is the lightest component of an inert scalar doublet which can induce dynamically electroweak symmetry breaking at one loop level. Moreover, in a large fraction of the parameter space of this model, the mass of the dark matter particle is essentially determined by the electroweak scale, so that the fact that the WIMP DM mass is around the electroweak scale is not a coincidence.

  14. Sum rules for the spontaneous chiral symmetry breaking parameters of QCD

    International Nuclear Information System (INIS)

    Craigie, N.S.; Stern, J.

    1981-03-01

    We discuss in the spirit of the work of Shifman, Vainshtein and Zakharov (SVZ), sum rules involving current-current vacuum correlation functions, whose Wilson expansion starts off with the operators anti qq or (anti qq) 2 , and thus provide information about the chiral symmetry breaking parameters of QCD. We point out that under the type of crude approximations made by SVZ, a value of sub(vac) (250MeV) 3 is obtained from one of these sum rules, in agreement with current expectations. Further we show that a Borel transformed version of the Weinberg sum rule, for VV - AA, current products seem only to make sense for an A 1 mass close to 1.3GeV and it makes little sense with the current algebra mass Msub(A)=anti 2M. We also give an estimate for the chiral symmetry breaking parameters μ 1 6 =2 2 (anti qsub(L) lambda sup(a)γsub(μ)qsub(L))(anti qsub(R) lambdasup(a) γsup(μ)qsub(R)) >sub(vac) entering in the Weinberg sum rules and μ 2 6 =g 2 sub(vac) entering in a new sum rule we propose involving antisymmetric tensor currents J=anti q σsub(μnu) q. (author)

  15. Symmetry breaking in nematic liquid crystals: analogy with cosmology and magnetism.

    Science.gov (United States)

    Repnik, R; Ranjkesh, A; Simonka, V; Ambrozic, M; Bradac, Z; Kralj, S

    2013-10-09

    Universal behavior related to continuous symmetry breaking in nematic liquid crystals is studied using Brownian molecular dynamics. A three-dimensional lattice system of rod-like objects interacting via the Lebwohl-Lasher interaction is considered. We test the applicability of predictions originally derived in cosmology and magnetism. In the first part we focus on coarsening dynamics following the temperature driven isotropic-nematic phase transition for different quench rates. The behavior in the early coarsening regime supports predictions made originally by Kibble in cosmology. For fast enough quenches, symmetry breaking and causality give rise to a dense tangle of defects. When the degree of orientational ordering is large enough, well defined protodomains characterized by a single average domain length are formed. With time subcritical domains gradually vanish and supercritical domains grow with time, exhibiting a universal scaling law. In the second part of the paper we study the impact of random-field-type disorder on a range of ordering in the (symmetry broken) nematic phase. We demonstrate that short-range order is observed even for a minute concentration of impurities, giving rise to disorder in line with the Imry-Ma theorem prediction only for the appropriate history of systems.

  16. The spectral density of the QCD Dirac operator and patterns of chiral symmetry breaking

    International Nuclear Information System (INIS)

    Toublan, D.; Verbaarschot, J.J.M.

    1999-01-01

    We study the spectrum of the QCD Dirac operator for two colors with fermions in the fundamental representation and for two or more colors with adjoint fermions. For N f flavors, the chiral flavor symmetry of these theories is spontaneously broken according to SU (2N f → Sp (2N f ) and SU (N f → O (N f ), respectively, rather than the symmetry breaking pattern SU (N f ) x SU (N f ) → SU (N f ) for QCD with three or more colors and fundamental fermions. In this paper we study the Dirac spectrum for the first two symmetry breaking patterns. Following previous work for the third case we find the Dirac spectrum in the domain λ QCD by means of partially quenched chiral perturbation theory. In particular, this result allows us to calculate the slope of the Dirac spectrum at λ = 0. We also show that for λ 2 Λ QCD (wing L the linear size of the system) the Dirac spectrum is given by a chiral Random Matrix Theory with the symmetries of the Dirac operator

  17. Heat-induced symmetry breaking in ant (Hymenoptera: Formicidae) escape behavior.

    Science.gov (United States)

    Chung, Yuan-Kai; Lin, Chung-Chi

    2017-01-01

    The collective egress of social insects is important in dangerous situations such as natural disasters or enemy attacks. Some studies have described the phenomenon of symmetry breaking in ants, with two exits induced by a repellent. However, whether symmetry breaking occurs under high temperature conditions, which are a common abiotic stress, remains unknown. In our study, we deposited a group of Polyrhachis dives ants on a heated platform and counted the number of escaping ants with two identical exits. We discovered that ants asymmetrically escaped through two exits when the temperature of the heated platform was >32.75°C. The degree of asymmetry increased linearly with the temperature of the platform. Furthermore, the higher the temperature of heated platform was, the more ants escaped from the heated platform. However, the number of escaping ants decreased for 3 min when the temperature was higher than the critical thermal limit (39.46°C), which is the threshold for ants to endure high temperature without a loss of performance. Moreover, the ants tended to form small groups to escape from the thermal stress. A preparatory formation of ant grouping was observed before they reached the exit, indicating that the ants actively clustered rather than accidentally gathered at the exits to escape. We suggest that a combination of individual and grouping ants may help to optimize the likelihood of survival during evacuation.

  18. Heat-induced symmetry breaking in ant (Hymenoptera: Formicidae escape behavior.

    Directory of Open Access Journals (Sweden)

    Yuan-Kai Chung

    Full Text Available The collective egress of social insects is important in dangerous situations such as natural disasters or enemy attacks. Some studies have described the phenomenon of symmetry breaking in ants, with two exits induced by a repellent. However, whether symmetry breaking occurs under high temperature conditions, which are a common abiotic stress, remains unknown. In our study, we deposited a group of Polyrhachis dives ants on a heated platform and counted the number of escaping ants with two identical exits. We discovered that ants asymmetrically escaped through two exits when the temperature of the heated platform was >32.75°C. The degree of asymmetry increased linearly with the temperature of the platform. Furthermore, the higher the temperature of heated platform was, the more ants escaped from the heated platform. However, the number of escaping ants decreased for 3 min when the temperature was higher than the critical thermal limit (39.46°C, which is the threshold for ants to endure high temperature without a loss of performance. Moreover, the ants tended to form small groups to escape from the thermal stress. A preparatory formation of ant grouping was observed before they reached the exit, indicating that the ants actively clustered rather than accidentally gathered at the exits to escape. We suggest that a combination of individual and grouping ants may help to optimize the likelihood of survival during evacuation.

  19. Localized Symmetry Breaking for Tuning Thermal Expansion in ScF 3 Nanoscale Frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Lei [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China; Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Qin, Feiyu [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China; Sanson, Andrea [Department of Physics and Astronomy, University of Padova, Padova I-35131, Italy; Huang, Liang-Feng [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Pan, Zhao [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China; Li, Qiang [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China; Sun, Qiang [International Laboratory for Quantum Functional Materials of Henan, School of Physics and Engineering, Zhengzhou University, Zhengzhou 450001, China; Wang, Lu [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China; Guo, Fangmin [X-Ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States; Aydemir, Umut [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Department of Chemistry, Koc University, Sariyer, Istanbul 34450, Turkey; Ren, Yang [X-Ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States; Sun, Chengjun [X-Ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439, United States; Deng, Jinxia [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China; Aquilanti, Giuliana [Elettra Sincrotrone Trieste, Basovizza, Trieste I-34149, Italy; Rondinelli, James M. [Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States; Chen, Jun [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China; Xing, Xianran [Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China

    2018-03-15

    The local symmetry, beyond the averaged crystallographic structure, tends to bring unu-sual performances. Negative thermal expansion is a peculiar physical property of solids. Here, we report the delicate design of the localized symmetry breaking to achieve the controllable thermal expansion in ScF3 nano-scale frameworks. Intriguingly, an isotropic zero thermal expansion is concurrently engi-neered by localized symmetry breaking, with a remarkably low coefficient of thermal expansion of about +4.0×10-8/K up to 675K. This mechanism is investigated by the joint analysis of atomic pair dis-tribution function of synchrotron X-ray total scattering and extended X-ray absorption fine structure spectra. A localized rhombohedral distortion presumably plays a critical role in stiffening ScF3 nano-scale frameworks and concomitantly suppressing transverse thermal vibrations of fluorine atoms. This physical scenario is also theoretically corroborated by the extinction of phonon modes with negative Grüneisen parameters in the rhombohedral ScF3. The present work opens an untraditional chemical modification to achieve controllable thermal expansion by breaking local symmetries of materials.

  20. Effects of ridge cracking and interface sliding on morphological symmetry breaking in straight-sided blisters

    Science.gov (United States)

    Li, Shi-Chen; Yu, Sen-Jiang; He, Linghui; Ni, Yong

    2018-03-01

    Complex surface patterns generated by nonlinear buckling originate from various symmetry-breaking instabilities. Identifying possible key factors that regulate the instability modes is critical to reveal the mechanism of the surface pattern selection. In this paper, how another two factors (ridge cracking and interface sliding) including Poisson's ratio influence the morphological symmetry breaking in straight-sided blisters are systematically studied. Morphology diagrams from stability analysis show that ridge cracking and low Poisson's ratio promote symmetric instability mode and favor bubble-like blisters while interface sliding and high Poisson's ratio facilitate antisymmetric instability mode and result in telephone cord buckles. The analytical predictions are evidenced by experimental observations on annealed silicon nitride films on glass substrates and confirmed by nonlinear numerical simulations. This study explains how and why the rarely observed bubble-like blisters in accompany with ridge crack can appear in brittle thin films in comparison with the ubiquitously observed telephone cord buckles that usually form as the development of an antisymmetric instability mode when straight-sided blisters undergo the super-critical isotropic compression.

  1. Symmetry-breaking in the H2@C60 endofullerene revealed by inelastic neutron scattering at low temperature.

    Science.gov (United States)

    Mamone, Salvatore; Johnson, Mark R; Ollivier, Jacques; Rols, Stéphane; Levitt, Malcolm H; Horsewill, Anthony J

    2016-01-21

    The fine structure of the rotational ground state of molecular ortho-hydrogen confined inside the fullerene cage C60 is investigated by inelastic neutron scattering (INS). The INS line corresponding to transitions between the three sub-levels comprising the ortho ground state to the non-degenerate para ground state was studied as a function of temperature down to 60 mK in neutron energy gain. The experiments show that at ambient pressure the three ortho sub-levels are split into a low energy non-degenerate level and a high energy doubly degenerate level separated by 0.135 ± 0.010 meV. This observation is consistent with hydrogen molecules being located at sites with axial symmetry superseding the icosahedral symmetry of isolated rigid C60 cages in the solid phase. To gain insight into the role of inter-cage interactions in determining the symmetry breaking potential, the effects of hydrostatic pressure on the fine structure of the line was also investigated. The analysis of the INS spectra shows that the potential and the energy levels of H2 are sensitive to the orientation of neighbouring cages, consistent with the low-temperature crystalline phase of C60.

  2. Decamethylytterbocene complexes of bipyridines and diazabutadines: multiconfigurational ground states and open-shell singlet formation

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Eric D [Los Alamos National Laboratory; Booth, C H [LBNL; Walter, M D [LBNL; Kazhdan, D [LBNL; Hu, Y - J [LBNL; Lukens, Wayne [LBNL; Maron, Laurent [INSA TOULOUSE; Eisentein, Odile [UNIV MONTPELLIER 2; Anderson, Richard [LBNL

    2009-01-01

    Partial ytterbium f-orbital occupancy (i.e. intermediate valence) and open-shell singlet Draft 12/formation are established for a variety of bipyridine and diazabutadiene adducts to decamethylytterbocene, (C{sub 5}Me{sub 5}){sub 2}Yb or Cp*{sub 2}Yb. Data used to support this claim includes ytterbium valence measurements using Yb Lm-edge x-ray absorption near-edge structure (XANES) spectroscopy, magnetic susceptibility and Complete Active Space Self-Consistent Field (CASSCF) multi configurational calculations, as well as structural measurements compared to density-functional theory (DFT) calculations. The CASSCF calculations indicate that the intermediate valence is the result of a multiconfigurational ground state wave function that has both an open-shell singlet f{sup 13} and a closed-shell singlet f{sup 14} component. A number of other competing theories for the unusual magnetism in these materials are ruled out by the presence of intermediate valence and its lack of any significant temperature dependence. These results have implications for understanding chemical bonding not only in organolanthanide complexes, but also for organometallic chemistry in general, as well as understanding magnetic interactions in nanopartic1es and devices.

  3. Time-reversal symmetry breaking superconductivity in the coexistence phase with magnetism in Fe pnictides.

    Science.gov (United States)

    Hinojosa, Alberto; Fernandes, Rafael M; Chubukov, Andrey V

    2014-10-17

    We argue that superconductivity in the coexistence region with spin-density-wave (SDW) order in weakly doped Fe pnictides erdiffers qualitatively from the ordinary s(+-) state outside the coexistence region as it develops an additional gap component which is a mixture of intrapocket singlet (s(++)) and interpocket spin-triplet pairings (the t state). The coupling constant for the t channel is proportional to the SDW order and involves interactions that do not contribute to superconductivity outside of the SDW region. We argue that the s(+-)- and t-type superconducting orders coexist at low temperatures, and the relative phase between the two is, in general, different from 0 or π, manifesting explicitly the breaking of the time-reversal symmetry promoted by long-range SDW order. We argue that time reversal may get broken even before true superconductivity develops.

  4. Dynamical Time-Reversal Symmetry Breaking and Photo-Induced Chiral Spin Liquid in Frustrated Mott Insulators

    Science.gov (United States)

    Claassen, Martin; Jiang, Hong-Chen; Moritz, Brian; Devereaux, Thomas

    Spurred by recent progress in melting, enhancement and induction of electronic order out of equilibrium, a tantalizing prospect concerns instead accessing transient Floquet steady states via broad pump pulses, to manipulate band topology and affect electronic transport. Here, we extend these ideas to strongly-correlated systems and show that pumping frustrated Mott insulators with circularly-polarized light can drive the effective spin system across a phase transition to a chiral spin liquid (CSL). Starting from a Kagome Hubbard model deep in the Mott phase, circular polarization promotes a scalar spin chirality Si . (Sj ×Sk) term directly to the Hamiltonian level, dynamically breaking time-reversal while preserving SU(2) spin symmetry. We find that the transient physics is well-captured by an effective Floquet spin model, fingerprint its phase diagram, and find a stable photo-induced CSL in close proximity to the equilibrium state. The results presented suggest a new avenue of employing dynamical symmetry breaking to engineer quantum spin liquids and access elusive phase transitions that are not readily accessible in equilibrium.

  5. Effects of Intermolecular Coupling on Excimer Formation and Singlet Fission

    Science.gov (United States)

    Mauck, Catherine McKay

    compelling strategy for improving organic photovoltaic device efficiencies. The formation of triplet states through singlet fission can be characterized using femtosecond visible transient absorption spectroscopy (fsTA). However, in PDI, the triplet-triplet absorption spectrum is strongly overlapped with the ground state bleach absorption. Here, a dyad molecule where PDI is covalently attached to an apocarotene triplet acceptor is synthesized, and studied in solution aggregates and thin films with fsTA, to demonstrate that apocarotene can be used as a sensitive spectral tag for triplet formation in PDI due to triplet-triplet energy transfer from PDI to the carotenoid. The efficiency of singlet fission in DPP can be tuned by modulating the crystal packing in the solid state. By synthesizing 3,6-bis(thiophene) derivatives of DPP with a series of different sidechains, thin film DPP singlet fission is related to the crystal structure intermolecular geometries, to more precisely determine the relationship between interchromophore coupling and singlet fission rate, which will inform the design of more robust chromophores for singlet fission. Finally, the role of the dielectric environment and stabilization of charge transfer configurations and charge transfer states is explored in DPP singlet fission, through aqueous nanoparticles of 3,6-bis(phenylthiophene) with different surface area-to-volume ratios, and a covalently linked dimer of DPP in solvents of varying polarity which can undergo symmetry-breaking charge separation.

  6. PT -symmetry breaking for the scattering problem in a one-dimensional non-Hermitian lattice model

    Science.gov (United States)

    Zhu, Baogang; Lü, Rong; Chen, Shu

    2016-03-01

    We study the PT -symmetry breaking for the scattering problem in a one-dimensional non-Hermitian tight-binding lattice model with balanced gain and loss distributed on two adjacent sites. In the scattering process the system undergoes a transition from the exact PT -symmetric phase to the phase with spontaneously breaking PT symmetry as the amplitude of complex potentials increases. Using the S-matrix method, we derive an exact discriminant, which can be used to distinguish different symmetry phases, and determine the exceptional point for the symmetry breaking analytically. In the PT -symmetry-breaking region, we also confirm the appearance of the unique feature, i.e., the coherent perfect absorption laser, in this simple non-Hermitian lattice model. The study of the scattering problem of such a simple model provides an additional way to unveil the physical effect of non-Hermitian PT -symmetric potentials.

  7. Light-front quantized field theory: (an introduction). Spontaneous symmetry breaking. Phase transition in φ4 theory

    International Nuclear Information System (INIS)

    Srivastava, P.P.

    1993-01-01

    The field theory quantized on the light-front is compared with the conventional equal-time quantized theory. The arguments based on the micro causality principle would imply that the light-front field theory may become nonlocal with respect to the longitudinal coordinate even though the corresponding equal-time formulation is local. This is found to be the case for the scalar theory. The conventional instant form theory is sometimes required to be constrained by invoking external physical considerations; the analogous conditions seem to be already built in the theory on the light-front. In spite of the different mechanisms of the spontaneous symmetry breaking in the two forms of dynamics they result in the same physical content. The phase transition in (φ 4 ) 2 theory is also discussed. The symmetric vacuum state for vanishingly small couplings is found to turn into an unstable symmetric one when the coupling is increased and may result in a phase transition of the second order in contrast to the first order transition concluded from the usual variational methods. (author)

  8. Proper and improper zero energy modes in Hartree-Fock theory and their relevance for symmetry breaking and restoration.

    Science.gov (United States)

    Cui, Yao; Bulik, Ireneusz W; Jiménez-Hoyos, Carlos A; Henderson, Thomas M; Scuseria, Gustavo E

    2013-10-21

    We study the spectra of the molecular orbital Hessian (stability matrix) and random-phase approximation (RPA) Hamiltonian of broken-symmetry Hartree-Fock solutions, focusing on zero eigenvalue modes. After all negative eigenvalues are removed from the Hessian by following their eigenvectors downhill, one is left with only positive and zero eigenvalues. Zero modes correspond to orbital rotations with no restoring force. These rotations determine states in the Goldstone manifold, which originates from a spontaneously broken continuous symmetry in the wave function. Zero modes can be classified as improper or proper according to their different mathematical and physical properties. Improper modes arise from symmetry breaking and their restoration always lowers the energy. Proper modes, on the other hand, correspond to degeneracies of the wave function, and their symmetry restoration does not necessarily lower the energy. We discuss how the RPA Hamiltonian distinguishes between proper and improper modes by doubling the number of zero eigenvalues associated with the latter. Proper modes in the Hessian always appear in pairs which do not double in RPA. We present several pedagogical cases exemplifying the above statements. The relevance of these results for projected Hartree-Fock methods is also addressed.

  9. Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5.

    Science.gov (United States)

    Ronning, F; Helm, T; Shirer, K R; Bachmann, M D; Balicas, L; Chan, M K; Ramshaw, B J; McDonald, R D; Balakirev, F F; Jaime, M; Bauer, E D; Moll, P J W

    2017-08-17

    Electronic nematic materials are characterized by a lowered symmetry of the electronic system compared to the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. Such nematic phases appear in the copper- and iron-based high-temperature superconductors, and their role in establishing superconductivity remains an open question. Nematicity may take an active part, cooperating or competing with superconductivity, or may appear accidentally in such systems. Here we present experimental evidence for a phase of fluctuating nematic character in a heavy-fermion superconductor, CeRhIn 5 (ref. 5). We observe a magnetic-field-induced state in the vicinity of a field-tuned antiferromagnetic quantum critical point at H c  ≈ 50 tesla. This phase appears above an out-of-plane critical field H* ≈ 28 tesla and is characterized by a substantial in-plane resistivity anisotropy in the presence of a small in-plane field component. The in-plane symmetry breaking has little apparent connection to the underlying lattice, as evidenced by the small magnitude of the magnetostriction anomaly at H*. Furthermore, no anomalies appear in the magnetic torque, suggesting the absence of metamagnetism in this field range. The appearance of nematic behaviour in a prototypical heavy-fermion superconductor highlights the interrelation of nematicity and unconventional superconductivity, suggesting nematicity to be common among correlated materials.

  10. Biaxial stress driven tetragonal symmetry breaking and high-temperature ferromagnetic semiconductor from half-metallic CrO2

    Science.gov (United States)

    Xiao, Xiang-Bo; Liu, Bang-Gui

    2018-03-01

    It is highly desirable to combine the full spin polarization of carriers with modern semiconductor technology for spintronic applications. For this purpose, one needs good crystalline ferromagnetic (or ferrimagnetic) semiconductors with high Curie temperatures. Rutile CrO2 is a half-metallic spintronic material with Curie temperature 394 K and can have nearly full spin polarization at room temperature. Here, we find through first-principles investigation that when a biaxial compressive stress is applied on rutile CrO2, the density of states at the Fermi level decreases with the in-plane compressive strain, there is a structural phase transition to an orthorhombic phase at the strain of -5.6 % , and then appears an electronic phase transition to a semiconductor phase at -6.1 % . Further analysis shows that this structural transition, accompanying the tetragonal symmetry breaking, is induced by the stress-driven distortion and rotation of the oxygen octahedron of Cr, and the half-metal-semiconductor transition originates from the enhancement of the crystal field splitting due to the structural change. Importantly, our systematic total-energy comparison indicates the ferromagnetic Curie temperature remains almost independent of the strain, near 400 K. This biaxial stress can be realized by applying biaxial pressure or growing the CrO2 epitaxially on appropriate substrates. These results should be useful for realizing full (100%) spin polarization of controllable carriers as one uses in modern semiconductor technology.

  11. Spontaneous symmetry breaking of (1+1)-dimensional φ4 theory in light-front field theory. II

    International Nuclear Information System (INIS)

    Pinsky, S.S.; van de Sande, B.

    1994-01-01

    We discuss spontaneous symmetry breaking of (1+1)-dimensional φ 4 theory in light-front field theory using a Tamm-Dancoff truncation. We show that, even though light-front field theory has a simple vacuum state which is an eigenstate of the full Hamiltonian, the field can develop a nonzero vacuum expectation value. This occurs because the zero mode of the field must satisfy an operator-valued constraint equation. In the context of (1+1)-dimensional φ 4 theory we present solutions to the constraint equation using a Tamm-Dancoff truncation to a finite number of particles and modes. We study the behavior of the zero mode as a function of coupling and Fock space truncation. The zero mode introduces new interactions into the Hamiltonian which breaks the Z 2 symmetry of the theory when the coupling is stronger than the critical coupling. We investigate the energy spectrum in the symmetric and broken phases, show that the theory does not break down in the vicinity of the critical coupling, and discuss the connection to perturbation theory. Finally, we study the spectrum of the field φ and show that, in the broken phase, the field is localized away from φ=0 as one would expect from equal-time calculations. We explicitly show that tunneling occurs

  12. Superconducting 2D system with lifted spin degeneracy: mixed singlet-triplet state.

    Science.gov (United States)

    Gor'kov, L P; Rashba, E I

    2001-07-16

    Motivated by recent experimental findings, we have developed a theory of the superconducting state for 2D metals without inversion symmetry modeling the geometry of a surface superconducting layer in a field-effect transistor or near the boundary doped by adsorbed ions. In such systems the twofold spin degeneracy is lifted by spin-orbit interaction, and singlet and triplet pairings are mixed in the wave function of the Cooper pairs. As a result, spin magnetic susceptibility becomes anisotropic and Knight shift retains finite and rather high value at T = 0.

  13. Superconducting 2D System with Lifted Spin Degeneracy: Mixed Singlet-Triplet State

    Energy Technology Data Exchange (ETDEWEB)

    Gor' kov, Lev P.; Rashba, Emmanuel I.

    2001-07-16

    Motivated by recent experimental findings, we have developed a theory of the superconducting state for 2D metals without inversion symmetry modeling the geometry of a surface superconducting layer in a field-effect transistor or near the boundary doped by adsorbed ions. In such systems the twofold spin degeneracy is lifted by spin-orbit interaction, and singlet and triplet pairings are mixed in the wave function of the Cooper pairs. As a result, spin magnetic susceptibility becomes anisotropic and Knight shift retains finite and rather high value at T=0 .

  14. Correlated Pair States Formed by Singlet Fission and Exciton-Exciton Annihilation.

    Science.gov (United States)

    Scholes, Gregory D

    2015-12-24

    Singlet fission to form a pair of triplet excitations on two neighboring molecules and the reverse process, triplet-triplet annihilation to upconvert excitation, have been extensively studied. Comparatively little work has sought to examine the properties of the intermediate state in both of these processes-the bimolecular pair state. Here, the eigenstates constituting the manifold of 16 bimolecular pair excitations and their relative energies in the weak-coupling regime are reported. The lowest-energy states obtained from the branching diagram method are the triplet pairs with overall singlet spin |X1⟩ ≈ (1)[TT] and quintet spin |Q⟩ ≈ (5)[TT]. It is shown that triplet pair states can be separated by a triplet-triplet energy-transfer mechanism to give a separated, yet entangled triplet pair (1)[T···T]. Independent triplets are produced by decoherence of the separated triplet pair. Recombination of independent triplets by exciton-exciton annihilation to form the correlated triplet pair (i.e., nongeminate recombination) happens with 1/3 of the rate of either triplet migration or recombination of the separated correlated triplet pair (geminate recombination).

  15. Accretion of a symmetry-breaking scalar field by a Schwarzschild black hole.

    Science.gov (United States)

    Traykova, Dina; Braden, Jonathan; Peiris, Hiranya V

    2018-03-06

    We simulate the behaviour of a Higgs-like field in the vicinity of a Schwarzschild black hole using a highly accurate numerical framework. We consider both the limit of the zero-temperature Higgs potential and a toy model for the time-dependent evolution of the potential when immersed in a slowly cooling radiation bath. Through these numerical investigations, we aim to improve our understanding of the non-equilibrium dynamics of a symmetry-breaking field (such as the Higgs) in the vicinity of a compact object such as a black hole. Understanding this dynamics may suggest new approaches for studying properties of scalar fields using black holes as a laboratory.This article is part of the Theo Murphy meeting issue 'Higgs Cosmology'. © 2018 The Author(s).

  16. Self-assembly of subwavelength nanostructures with symmetry breaking in solution

    Science.gov (United States)

    Tian, Xiang-Dong; Chen, Shu; Zhang, Yue-Jiao; Dong, Jin-Chao; Panneerselvam, Rajapandiyan; Zhang, Yun; Yang, Zhi-Lin; Li, Jian-Feng; Tian, Zhong-Qun

    2016-01-01

    Nanostructures with symmetry breaking can allow the coupling between dark and bright plasmon modes to induce strong Fano resonance. However, it is still a daunting challenge to prepare bottom-up self-assembled subwavelength asymmetric nanostructures with appropriate gaps between the nanostructures especially below 5 nm in solution. Here we present a viable self-assembly method to prepare symmetry-breaking nanostructures consisting of Ag nanocubes and Au nanospheres both with tunable size (90-250 nm for Au nanospheres; 100-160 nm for Ag nanocubes) and meanwhile control the nanogaps through ultrathin silica shells of 1-5 nm thickness. The Raman tag of 4-mercaptobenzoic acid (MBA) assists the self-assembly process and endows the subwavelength asymmetric nanostructures with surface-enhanced Raman scattering (SERS) activity. Moreover, thick silica shells (above 50 nm thickness) can be coated on the self-assembled nanostructures in situ to stabilize the whole nanostructures, paving the way toward bioapplications. Single particle scattering spectroscopy with a 360° polarization resolution is performed on individual Ag nanocube and Au nanosphere dimers, correlated with high-resolution TEM characterization. The asymmetric dimers exhibit strong configuration and polarization dependence Fano resonance properties. Overall, the solution-based self-assembly method reported here is opening up new opportunities to prepare diverse multicomponent nanomaterials with optimal performance.Nanostructures with symmetry breaking can allow the coupling between dark and bright plasmon modes to induce strong Fano resonance. However, it is still a daunting challenge to prepare bottom-up self-assembled subwavelength asymmetric nanostructures with appropriate gaps between the nanostructures especially below 5 nm in solution. Here we present a viable self-assembly method to prepare symmetry-breaking nanostructures consisting of Ag nanocubes and Au nanospheres both with tunable size (90-250 nm

  17. Symmetry breaking of localized discrete matter waves induced by spin–orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Salerno, M. [Dipartimento di Fisica “E.R. Caianiello”, CNISM and INFN–Gruppo Collegato di Salerno, Universitá di Salerno, Via Giovanni Paolo II, 84084 Fisciano (Italy); Abdullaev, F.Kh., E-mail: fatkhulla@yahoo.com [Department of Physics, Kulliyyah of Science, International Islamic University of Malaysia, 25200 Kuantan, Pahang (Malaysia)

    2015-10-02

    We study localized nonlinear excitations of a dilute Bose–Einstein condensate (BEC) with spin–orbit coupling in a deep optical lattice (OL). For this we introduce a tight-binding model that includes the spin–orbit coupling (SOC) at the discrete level in the form of a generalized discrete nonlinear Schrödinger equation. Existence and stability of discrete solitons of different symmetry types is demonstrated. Quite interestingly, we find three distinctive regions in which discrete solitons undergo spontaneously symmetry breaking, passing from on-site to inter-site and to asymmetric, simply by varying the interatomic interactions. Existence ranges of discrete solitons with inter-site symmetry depend on SOC and shrink to zero as the SOC parameter is increased. Asymmetric discrete solitons appear as novel excitations specific of the SOC. Possible experimental implementation of these results is briefly discussed.

  18. Charged tensor matter fields and Lorentz symmetry violation via spontaneous symmetry breaking

    International Nuclear Information System (INIS)

    Colatto, L.P.; Penna, A.L.A.; Santos, W.C.

    2003-10-01

    We consider a model with a charged vector field along with a Cremmer-Scherk-Kalb-Ramond (CSKR) matter field coupled to a U(1) gauge potential. We obtain a natural Lorentz symmetry violation due to the local U(1) spontaneous symmetry breaking mechanism triggered by the imaginary part of the vector matter. The choice of the unitary gauge leads to the decoupling of the gauge-Kr sector from the Higgs-Kr sector. The excitation spectrum is carefully analyzed and the physical modes are identified. We propose an identification of the neutral massive spin-1 Higgs-like field with the massive Z' boson of the so-called mirror matter models. (author)

  19. Charge symmetry breaking in the reaction np → dπ0

    International Nuclear Information System (INIS)

    Opper, A.K.; Auld, E.G.; Churchman, R.M.; Davis, C.A.; Finlay, R.W.; Green, P.W.; Greeniaus, L.G.; Hutcheon, D.A.; Jordan, D.V.; Korkmaz, E.J.; Niskanen, J.A.; O'Rielly, G.V.; Porcelli, T.; Reitzner, S.D.; Walden, P.L.; Yen, S.

    2000-01-01

    Charge Symmetry Breaking (CSB) in the strong interaction is due ultimately to the mass difference between the u and d quarks, but is described conveniently by meson-exchange models. TRIUMF experiment E704 measures the foreward-backward asymmetry (A fb ) in np→dπ 0 , which must be zero in the centre-of-mass if charge symmetry is conserved. The angle-integrated value of A fb is calculated to be -35x10 -4 near 280 MeV with the dominant contribution coming from (π 0 -η) and (π 0 -η') mixing. The experiment uses a neutron beam of 279.5 MeV, a liquid hydrogen target, and the SASP spectrometer to detect deuterons from the np→dπ 0 reaction. A measurement of the pp→dπ + distribution, for which A fb must be zero, provides a strong test of systematic errors

  20. Dynamical Chiral Symmetry Breaking in the Multi-Instanton Vacuum of QCD

    Science.gov (United States)

    Watabe, T.; Fukushima, M.; Toki, H.

    2000-10-01

    We study the properties of SU(Nf) light quarks in the multi-instanton vacuum of QCD. We formulate the dynamical symmetry breaking for light quarks of various numbers of flavor Nf with the inclusion of the instanton size distribution. We find that the quark mass function increases rapidly toward small Euclidean momenta when the finite size distribution is introduced with a power law fall-off of large instanton size, ρ-n (n > 3). We observe a confining feature of light quarks for small fall-off parameter n and for large packing fraction bar {ρ }/bar {R} in the behavior of the quark mass function extrapolated to the time-like region.

  1. Symmetry breaking and adaptation: evidence from a 'toy model' of a virus.

    Science.gov (United States)

    Vargas, J M; Stephens, C R; Waelbroeck, H; Zertuche, F

    1999-07-01

    We argue that an induced breaking of the genetic synonym symmetry due to the action of genetic operators such as mutation can enhance the adaptability of a species to changes in the environment. In the case of a virus, the claim is that the codon bias in the neutralization epitope improves the virus' ability to generate mutants that evade the induced immune response. We support our claim with a simple 'toy model' of a viral epitope evolving in competition with the immune system. The effective selective advantage of a higher mutability leads to a dominance of codons that favor non-synonymous mutations. As further evidence we present a simple model for a genetic regulatory network that leads to adaptive evolution in a population of giraffes by means of an induced symmetry breaking rather than through any direct selective advantage.

  2. Accretion of a symmetry-breaking scalar field by a Schwarzschild black hole

    Science.gov (United States)

    Traykova, Dina; Braden, Jonathan; Peiris, Hiranya V.

    2018-01-01

    We simulate the behaviour of a Higgs-like field in the vicinity of a Schwarzschild black hole using a highly accurate numerical framework. We consider both the limit of the zero-temperature Higgs potential and a toy model for the time-dependent evolution of the potential when immersed in a slowly cooling radiation bath. Through these numerical investigations, we aim to improve our understanding of the non-equilibrium dynamics of a symmetry-breaking field (such as the Higgs) in the vicinity of a compact object such as a black hole. Understanding this dynamics may suggest new approaches for studying properties of scalar fields using black holes as a laboratory. This article is part of the Theo Murphy meeting issue `Higgs Cosmology'.

  3. Recent Results from CMS and ATLAS: Electroweak Symmetry, Breaking and Beyond

    CERN Document Server

    Azzurri, Paolo

    2016-01-01

    The discovery of the Higgs boson, announced by the CMS and ATLAS collaborations in 2012, unearthed the final cornerstone of the standard electroweak model of particle physics, and repre- sents the main legacy of the LHC Run 1. With Run 1 data the mass of the Higgs boson has been determined with 0.2pct precision, while coupling properties are only established at the 10pct level or worse. As the picture of the minimal standard model is now complete, unsettled difficulties and open questions remain on its stage. The LHC Run 2 has successfully started in 2015, opening a new period of particle physics exploration, at higher energy and intensity it will undoubtedly de- liver more insight on the electroweak model, its symmetry breaking mechanism, and on possible solutions to its difficulties.

  4. Critical dynamics of spontaneous symmetry breaking in a homogeneous Bose gas

    Science.gov (United States)

    Gaunt, Alexander; Navon, Nir; Smith, Robert; Hadzibabic, Zoran

    2015-05-01

    Kibble-Zurek theory models the dynamics of spontaneous symmetry breaking, which plays an important role in a wide variety of physical contexts, ranging from cosmology to superconductors. We explored these dynamics in a homogeneous system by thermally quenching an atomic gas with short-range interactions through the Bose-Einstein phase transition. Using homodyne matter-wave interferometry to measure first-order correlation functions, we verified the central quantitative prediction of the Kibble-Zurek theory, namely the homogeneous-system power-law scaling of the coherence length with the quench rate. Moreover, we directly confirmed its underlying hypothesis, the freezing of the correlation length near the transition. Our measurements agree with a beyond-mean-field theory and support the expectation that the dynamical critical exponent for this universality class is z=3/2.

  5. Electroweak symmetry breaking and mass spectra in six-dimensional gauge-Higgs grand unification

    Science.gov (United States)

    Hosotani, Yutaka; Yamatsu, Naoki

    2018-02-01

    The mass spectra of the standard model particles are reproduced in the SO(11) gauge-Higgs grand unification in six-dimensional warped space without introducing exotic light fermions. Light neutrino masses are explained by the gauge-Higgs seesaw mechanism. We evaluate the effective potential of the four-dimensional Higgs boson appearing as a fluctuation mode of the Aharonov-Bohm phase θ_H in the extra-dimensional space, and show that the dynamical electroweak symmetry breaking takes place with the Higgs boson mass m_H ˜ 125 GeV and θ_H ˜ 0.1. The Kaluza-Klein mass scale in the fifth dimension is approximately given by m_KK ˜ 1.230 TeV/sin θ_H.

  6. Symmetry breaking and restoring wave transmission in diode-antidiode double chains.

    Science.gov (United States)

    Lepri, Stefano; Malomed, Boris A

    2013-04-01

    We introduce a system of two parallel-coupled discrete nonlinear Schrödinger inhomogeneous chains. Each one favors the unidirectional transmission of incident packets, in the opposite directions with respect to each other. Two different configurations of the diode-antidiode pair are considered, i.e., a ladder and a plaquette. They feature, respectively, the uniform transverse linear coupling or the coupling limited to the central nonlinear segment of the system. In the case of weak linear coupling, the symmetry breaking is observed (i.e., the pair still features the diode behavior), while the moderately strong coupling restores the symmetry, making the transmission effectively bidirectional. In the case of the ladder, an oscillatory dependence of the transmission on the strength of the coupling is observed and qualitatively explained.

  7. Unidirectional molecular assembly alignment on graphene enabled by nanomechanical symmetry breaking.

    Science.gov (United States)

    Hong, Liu; Nishihara, Taishi; Hijikata, Yuh; Miyauchi, Yuhei; Itami, Kenichiro

    2018-02-05

    Precise fabrication of molecular assemblies on a solid surface has long been of central interest in surface science. Their perfectly oriented growth only along a desired in-plane direction, however, remains a challenge, because of the thermodynamical equivalence of multiple axis directions on a solid-surface lattice. Here we demonstrate the successful fabrication of an in-plane, unidirectional molecular assembly on graphene. Our methodology relies on nanomechanical symmetry breaking effects under atomic force microscopy tip scanning, which has never been used in molecular alignment. Individual one-dimensional (1D) molecular assemblies were aligned along a selected symmetry axis of the graphene lattice under finely-tuned scanning conditions after removing initially-adsorbed molecules. Experimental statistics and computational simulations suggest that the anisotropic tip scanning locally breaks the directional equivalence of the graphene surface, which enables nucleation of the unidirectional 1D assemblies. Our findings will open new opportunities in the molecular alignment control on various atomically flat surfaces.

  8. Quantum gases. Critical dynamics of spontaneous symmetry breaking in a homogeneous Bose gas.

    Science.gov (United States)

    Navon, Nir; Gaunt, Alexander L; Smith, Robert P; Hadzibabic, Zoran

    2015-01-09

    Kibble-Zurek theory models the dynamics of spontaneous symmetry breaking, which plays an important role in a wide variety of physical contexts, ranging from cosmology to superconductors. We explored these dynamics in a homogeneous system by thermally quenching an atomic gas with short-range interactions through the Bose-Einstein phase transition. Using homodyne matter-wave interferometry to measure first-order correlation functions, we verified the central quantitative prediction of the Kibble-Zurek theory, namely the homogeneous-system power-law scaling of the coherence length with the quench rate. Moreover, we directly confirmed its underlying hypothesis, the freezing of the correlation length near the transition. Our measurements agree with a beyond-mean-field theory and support the expectation that the dynamical critical exponent for this universality class is z = 3/2. Copyright © 2015, American Association for the Advancement of Science.

  9. Symmetry-Breaking Effect on the Electromagnetic Properties of Plasmonic Trimers Composed of Graphene Nanodisks

    Directory of Open Access Journals (Sweden)

    Weibin Qiu

    2018-03-01

    Full Text Available Plasmonic trimers composed of equal-sized graphene nanodisks are proposed in this paper. The symmetry-breaking effect on the electromagnetic properties of the nanostructure is numerically investigated by studying plasmon energy diagrams and optical scattering spectra in mid-infrared range with a gradient vertex angle. The degenerate plasmonic modes are lifted and new modes appear with increased vertex angle. The energy diagrams are consistent with scattering extinction spectra, about which the dipole moment distribution of the proposed structure is discussed to demonstrate the coupling strength of the collective plasmonic modes of the trimer. More specifically, the frequency tunability of the plasmonic trimer is pointed out by modifying the chemical potential of the graphene nanodisks without varying the geometric configuration. The proposed structure might find applications such as light-matter interaction, single molecule detection, and high-sensitivity chemical sensing.

  10. Rencontres de Moriond EW 2012: Addressing symmetry breaking and mass hierarchy

    CERN Multimedia

    Pauline Gagnon

    2012-01-01

    Last Friday at the Moriond conference in La Thuile in Italy, Lisa Randall from Harvard University reminded the audience how all fields are related: electroweak symmetry breaking must take into account flavour physics for example. Every good model should address this intrinsic connection.   Despite many expectations, no signs for supersymmetry (SUSY) of any type has been found to date. So Lisa Randall worked with Csaba Csaki and John Terning to explore alternatives and developed a version of supersymmetry built on the Minimal Composite Supersymmetry Standard Model (MCSSM) that Csaki, Shirman, and Terning had developed, incorporating a strongly interacting theory with compositeness that addresses among other things the fact that the top quark is so much heavier than all other quarks. Randall and collaborators showed that this model, when supersymmetry is incorporated, naturally accommodates both a Higgs boson around 125 GeV and a light stop, the supersymmetric partner to the top quark. &a...

  11. Small-scale properties of the KPZ equation and dynamical symmetry breaking

    Science.gov (United States)

    Hochberg, David; Molina-París, Carmen; Pérez-Mercader, Juan; Visser, Matt

    2001-01-01

    A functional integral technique is used to study the ultraviolet or short distance properties of the Kardar-Parisi-Zhang (KPZ) equation with white Gaussian noise. We apply this technique to calculate the one-loop effective potential for the KPZ equation. The effective potential is (at least) one-loop ultraviolet renormalizable in 1, 2, and 3 space dimensions, but non-renormalizable in 4 or higher space dimensions. This potential is intimately related to the probability distribution function (PDF) for the spacetime averaged field. For the restricted class of field configurations considered here, the KPZ equation exhibits dynamical symmetry breaking (DSB) via an analog of the Coleman-Weinberg mechanism in 1 and 2 space dimensions, but not in 3 space dimensions.

  12. Dynamical Electroweak Symmetry Breaking with a Heavy Fermion in Light of Recent LHC Results

    Directory of Open Access Journals (Sweden)

    Pham Q. Hung

    2013-01-01

    Full Text Available The recent announcement of a discovery of a possible Higgs-like particle—its spin and parity are yet to be determined—at the LHC with a mass of 126 GeV necessitates a fresh look at the nature of the electroweak symmetry breaking, in particular if this newly-discovered particle will turn out to have the quantum numbers of a Standard Model Higgs boson. Even if it were a 0+ scalar with the properties expected for a SM Higgs boson, there is still the quintessential hierarchy problem that one has to deal with and which, by itself, suggests a new physics energy scale around 1 TeV. This paper presents a minireview of one possible scenario: the formation of a fermion-antifermion condensate coming from a very heavy fourth generation, carrying the quantum number of the SM Higgs field, and thus breaking the electroweak symmetry.

  13. Penrose limit, spontaneous symmetry breaking, and holography in a pp-wave background

    International Nuclear Information System (INIS)

    Das, Sumit R.; Gomez, Cesar; Rey, Soo-Jong

    2002-01-01

    We argue that the gauge theory dual to the type IIB string theory in a ten-dimensional pp-wave background resides on a Euclidean subspace spanning four of the eight transverse coordinates. We then show that the evolution of the string along one of the light cone directions in the bulk is identifiable as the RG flow of the gauge theory, a relation facilitating the 'holography' of the pp-wave background. The 'holography' reorganizes the dual gauge theory into theories defined over Hilbert subspaces of fixed R charge. The reorganization breaks the SO(4,2)xSO(6) symmetry to a maximal subgroup SO(4)xSO(4) spontaneously. We argue that the low-energy string modes may be regarded as Goldstone modes resulting from such a symmetry breaking pattern

  14. Precision measurement of charge symmetry breaking in np elastic scattering at 347 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Abegg, R. [TRIUMF, Vancouver, BC (Canada); Berdoz, A.R.; Birchall, J. [Univ. of Manitoba, Winnipeg, Manitoba (Canada). Dept. of Physics] [and others

    1995-07-01

    Charge symmetry breaking in np elastic scattering at 347 MeV has been measured with high precision. From fits of the measured asymmetry curves over the angular range 53.4{degree} {le} {theta}{sub cm} {le} 86.9{degree}, the difference in the center-of-mass zero-crossing angles of the analyzing powers was determined to be 0.438{degree} {+-} 0.054{degree} (stat.) {+-} 0.051{degree} (syst.). Using the experimentally determined slope of the analyzing power, dA/d{theta} = ({minus}1.35 {+-} 0.05) {times} 10{sup {minus}2} deg{sup {minus}1}, this is equivalent to {Delta}A = [59 {+-} 7(stat.) {+-} 7(syst.) {+-} 2(syst.)] {times} 10{sup {minus}4}. Predictions of nucleon-nucleon interaction models based on meson exchange agree well with this result.

  15. Sum rules for the spontaneous-chiral-symmetry-breaking parameters of quantum chromodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Craigie, N.S.; Stern, J.

    1982-11-01

    We discuss in the spirit of the work of Shifman, Vainshtein, and Zakharov (SVZ), sum rules involving current-current vacuum correlation functions, whose Wilson expansion start off with the operators q-barq or (q-barq)/sup 2/, and thus provide information about the chiral-symmetry-breaking parameters of QCD. We point out that under the type of crude approximations made by SVZ, a value of /sub vac/ = (250 MeV)/sup 3/ is obtained from one of these sum rules, in agreement with current expectations. Further, we show that a Borel-transformed version of the Weinberg sum rule for VV-AA current products seems only to make sense for an A/sub 1/ mass close to 1.3 GeV and it makes little sense with the current-algebra mass M/sub A/ = 2M. We also give an estimate for the chiral-symmetry-breaking parameters ..mu../sub 1/ /sup 6/ = 2/sub vac/, entering in the Weinberg sum rules, and ..mu../sub 2/ /sup 6/ = g/sup 2/<(q-bar/sub R/lambda/sup a/sigma/sub munu/q/sub L/) (q-bar/sub R/lambda/sup a/sigma/sup munu/q/sub L/)>/sub vac/, entering in a new sum rule we propose, involving antisymmetric tensor currents J = q-barsigma/sub munu/q.

  16. Population structure induces a symmetry breaking favoring the emergence of cooperation.

    Directory of Open Access Journals (Sweden)

    Jorge M Pacheco

    2009-12-01

    Full Text Available The evolution of cooperation described in terms of simple two-person interactions has received considerable attention in recent years, where several key results were obtained. Among those, it is now well established that the web of social interaction networks promotes the emergence of cooperation when modeled in terms of symmetric two-person games. Up until now, however, the impacts of the heterogeneity of social interactions into the emergence of cooperation have not been fully explored, as other aspects remain to be investigated. Here we carry out a study employing the simplest example of a prisoner's dilemma game in which the benefits collected by the participants may be proportional to the costs expended. We show that the heterogeneous nature of the social network naturally induces a symmetry breaking of the game, as contributions made by cooperators may become contingent on the social context in which the individual is embedded. A new, numerical, mean-field analysis reveals that prisoner's dilemmas on networks no longer constitute a defector dominance dilemma--instead, individuals engage effectively in a general coordination game. We find that the symmetry breaking induced by population structure profoundly affects the evolutionary dynamics of cooperation, dramatically enhancing the feasibility of cooperators: cooperation blooms when each cooperator contributes the same cost, equally shared among the plethora of games in which she participates. This work provides clear evidence that, while individual rational reasoning may hinder cooperative actions, the intricate nature of social interactions may effectively transform a local dilemma of cooperation into a global coordination problem.

  17. Vibrational dynamics of aniline (N2)1 clusters in their first excited singlet state

    Science.gov (United States)

    Hineman, M. F.; Kim, S. K.; Bernstein, E. R.; Kelley, D. F.

    1992-04-01

    The first excited singlet state S1 vibrational dynamics of aniline(N2)1 clusters are studied and compared to previous results on aniline(CH4)1 and aniline(Ar)1. Intramolecular vibrational energy redistribution (IVR) and vibrational predissociation (VP) rates fall between the two extremes of the CH4 (fast IVR, slow VP) and Ar (slow IVR, fast VP) cluster results as is predicted by a serial IVR/VP model using Fermi's golden rule to describe IVR processes and a restricted Rice-Ramsperger-Kassel-Marcus (RRKM) theory to describe unimolecular VP rates. The density of states is the most important factor determining the rates. Two product states, 00 and 10b1, of bare aniline and one intermediate state ˜(00) in the overall IVR/VP process are observed and time resolved measurements are obtained for the 000 and ˜(000) transitions. The results are modeled with the serial mechanism described above.

  18. Photoinduced symmetry-breaking intramolecular charge transfer in a quadrupolar pyridinium derivative.

    Science.gov (United States)

    Carlotti, Benedetta; Benassi, Enrico; Spalletti, Anna; Fortuna, Cosimo G; Elisei, Fausto; Barone, Vincenzo

    2014-07-21

    We report here a joint experimental and theoretical study of a quadrupolar, two-branched pyridinium derivative of interest as a potential non-linear optical material. The spectral and photophysical behaviour of this symmetric system is greatly affected by the polarity of the medium. A very efficient photoinduced intramolecular charge transfer, surprisingly more efficient than in the dipolar asymmetric analogue, is found to occur by femtosecond resolved transient absorption spectroscopy. TD-DFT calculations are in excellent agreement with these experimental findings and predict large charge displacements in the molecular orbitals describing the ground state and the lowest excited singlet state. The theoretical study also revealed that in highly polar media the symmetry of the excited state is broken giving a possible explanation to the fluorescence and transient absorption spectra resembling those of the one-branched analogous compound in the same solvents. The present study may give an important insight into the excited state deactivation mechanism of cationic (donor-π-acceptor-π-donor)(+) quadrupolar compounds characterised by negative solvatochromism, which are expected to show significant two-photon absorption (TPA). Moreover, the water solubility of the investigated quadrupolar system may represent an added value in view of the most promising applications of TPA materials in biology and medicine.

  19. Induced quadrupolar singlet ground state of praseodymium in a modulated pyrochlore

    Science.gov (United States)

    van Duijn, J.; Kim, K. H.; Hur, N.; Ruiz-Bustos, R.; Adroja, D. T.; Bridges, F.; Daoud-Aladine, A.; Fernandez-Alonso, F.; Wen, J. J.; Kearney, V.; Huang, Q. Z.; Cheong, S.-W.; Perring, T. G.; Broholm, C.

    2017-09-01

    The complex structure and magnetism of Pr2 -xBixRu2O7 was investigated by neutron scattering and extended x-ray absorption fine structure. Pr has an approximate doublet ground state and the first excited state is a singlet. While the B -site (Ru) is well ordered throughout, this is not the case for the A -site (Pr/Bi). A broadened distribution for the Pr-O2 bond length at low temperature indicates the Pr environment varies from site to site even for x =0 . The environment about the Bi site is highly disordered ostensibly due to the 6 s lone pairs on Bi3 +. Correspondingly, we find that the non-Kramers doublet ground-state degeneracy, otherwise anticipated for Pr in the pyrochlore structure, is lifted so as to produce a quadrupolar singlet ground state with a spatially varying energy gap. For x =0 , below TN, the Ru sublattice orders antiferromagnetically, with propagation vector k =(0 ,0 ,0 ) as for Y2Ru2O7 . No ordering associated with the Pr sublattice is observed down to 100 mK. The low-energy magnetic response of Pr2 -xBixRu2O7 features a broad spectrum of magnetic excitations associated with inhomogeneous splitting of the Pr quasidoublet ground state. For x =0 (x =0.97 ), the spectrum is temperature dependent (independent). It appears disorder associated with Bi alloying enhances the inhomogeneous Pr crystal-field level splitting so that intersite interactions become irrelevant for x =0.97 . The structural complexity for the A -site may be reflected in the hysteretic uniform magnetization of B -site ruthenium in the Néel phase.

  20. Thermal transport in topological-insulator-based superconducting hybrid structures with mixed singlet and triplet pairing states.

    Science.gov (United States)

    Li, Hai; Zhao, Yuan Yuan

    2017-11-22

    In the framework of the Bogoliubov-de Gennes equation, we investigate the thermal transport properties in topological-insulator-based superconducting hybrid structures with mixed spin-singlet and spin-triplet pairing states, and emphasize the different manifestations of the spin-singlet and spin-triplet pairing states in the thermal transport signatures. It is revealed that the temperature-dependent differential thermal conductance strongly depends on the components of the pairing state, and the negative differential thermal conductance only occurs in the spin-singlet pairing state dominated regime. It is also found that the thermal conductance is profoundly sensitive to the components of the pairing state. In the spin-singlet pairing state controlled regime, the thermal conductance obviously oscillates with the phase difference and junction length. With increasing the proportion of the spin-triplet pairing state, the oscillating characteristic of the thermal conductance fades out distinctly. These results suggest an alternative route for distinguishing the components of pairing states in topological-insulator-based superconducting hybrid structures.

  1. Bimanual training in stroke: How do coupling and symmetry-breaking matter?

    Directory of Open Access Journals (Sweden)

    Berton Eric

    2011-01-01

    Full Text Available Abstract Background The dramatic consequences of stroke on patient autonomy in daily living activities urged the need for new reliable therapeutic strategies. Recently, bimanual training has emerged as a promising tool to improve the functional recovery of upper-limbs in stroke patients. However, who could benefit from bimanual therapy and how it could be used as a part of a more complete rehabilitation protocol remain largely unknown. A possible reason explaining this situation is that coupling and symmetry-breaking mechanisms, two fundamental principles governing bimanual behaviour, have been largely under-explored in both research and rehabilitation in stroke. Discussion Bimanual coordination emerges as an active, task-specific assembling process where the limbs are constrained to act as a single unit by virtue of mutual coupling. Consequently, exploring, assessing, re-establishing and exploiting functional bimanual synergies following stroke, require moving beyond the classical characterization of performance of each limb in separate and isolated fashion, to study coupling signatures at both neural and behavioural levels. Grounded on the conceptual framework of the dynamic system approach to bimanual coordination, we debated on two main assumptions: 1 stroke-induced impairment of bimanual coordination might be anticipated/understood by comparing, in join protocols, changes in coupling strength and asymmetry of bimanual discrete movements observed in healthy people and those observed in stroke; 2 understanding/predicting behavioural manifestations of decrease in bimanual coupling strength and/or increase in interlimb asymmetry might constitute an operational prerequisite to adapt therapy and better target training at the specific needs of each patient. We believe that these statements draw new directions for experimental and clinical studies and contribute in promoting bimanual training as an efficient and adequate tool to facilitate the

  2. One step replica symmetry breaking and extreme order statistics of logarithmic REMs

    Directory of Open Access Journals (Sweden)

    Xiangyu Cao, Yan V. Fyodorov, Pierre Le Doussal

    2016-12-01

    Full Text Available Building upon the one-step replica symmetry breaking formalism, duly understood and ramified, we show that the sequence of ordered extreme values of a general class of Euclidean-space logarithmically correlated random energy models (logREMs behave in the thermodynamic limit as a randomly shifted decorated exponential Poisson point process. The distribution of the random shift is determined solely by the large-distance ("infra-red", IR limit of the model, and is equal to the free energy distribution at the critical temperature up to a translation. the decoration process is determined solely by the small-distance ("ultraviolet", UV limit, in terms of the biased minimal process. Our approach provides connections of the replica framework to results in the probability literature and sheds further light on the freezing/duality conjecture which was the source of many previous results for log-REMs. In this way we derive the general and explicit formulae for the joint probability density of depths of the first and second minima (as well its higher-order generalizations in terms of model-specific contributions from UV as well as IR limits. In particular, we show that the second min statistics is largely independent of details of UV data, whose influence is seen only through the mean value of the gap. For a given log-correlated field this parameter can be evaluated numerically, and we provide several numerical tests of our theory using the circular model of $1/f$-noise.

  3. Planck-scale modifications to electrodynamics characterized by a spacelike symmetry-breaking vector

    International Nuclear Information System (INIS)

    Gubitosi, Giulia; Amelino-Camelia, Giovanni; Melchiorri, Alessandro; Genovese, Giuseppe

    2010-01-01

    In the study of Planck-scale ('quantum-gravity-induced') violations of Lorentz symmetry, an important role was played by the deformed-electrodynamics model introduced by Myers and Pospelov. Its reliance on conventional effective quantum field theory, and its description of symmetry-violation effects simply in terms of a four-vector with a nonzero component only in the time direction, rendered it an ideal target for experimentalists and a natural concept-testing ground for many theorists. At this point however the experimental limits on the single Myers-Pospelov parameter, after improving steadily over these past few years, are 'super-Planckian'; i.e. they take the model out of actual interest from a conventional quantum-gravity perspective. In light of this we here argue that it may be appropriate to move on to the next level of complexity, still with vectorial symmetry violation but adopting a generic four-vector. We also offer a preliminary characterization of the phenomenology of this more general framework, sufficient to expose a rather significant increase in complexity with respect to the original Myers-Pospelov setup. Most of these novel features are linked to the presence of spatial anisotropy, which is particularly pronounced when the symmetry-breaking vector is spacelike, and they are such that they reduce the bound-setting power of certain types of observations in astrophysics.

  4. Role of Symmetry Breaking on the Optical Transitions in Lead-Salt Quantum Dots

    KAUST Repository

    Nootz, Gero

    2010-09-08

    The influence of quantum confinement on the one- and two-photon absorption spectra (1PA and 2PA) of PbS and PbSe semiconductor quantum dots (QDs) is investigated. The results show 2PA peaks at energies where only 1PA transitions are predicted and 1PA peaks where only 2PA transitions are predicted by the often used isotropic k•p four-band envelope function formalism. The first experimentally identified two-photon absorption peak coincides with the energy of the first one photon allowed transition. This first two-photon peak cannot be explained by band anisotropy, verifying that the inversion symmetry of the wave functions is broken and relaxation of the parity selection rules has to be taken into account to explain optical transitions in lead-salt QDs. Thus, while the band anisotropy of the bulk semiconductor plays a role in the absorption spectra, especially for the more anisotropic PbSe QDs, a complete model of the absorption spectra, for both 1PA and 2PA, must also include symmetry breaking of the quantum confined wave functions. These studies clarify the controversy of the origin of spectral features in lead-salt QDs. © 2010 American Chemical Society.

  5. Z → bb-bar probability and asymmetry in a model of dynamical electroweak symmetry breaking

    International Nuclear Information System (INIS)

    Arbuzov, B.A.; Osipov, M.Yu.

    1997-01-01

    The deviations from the standard model in the probability of Z → bb-bar decay and in the forward-backward asymmetry in the reaction e + e - → bb-bar are studied in the framework of the model of dynamical electroweak symmetry breaking, the basic point of which is the existence of a triple anomalous W-boson vertex in a region of momenta restricted by a cutoff. A set of equations for additional terms in the W b t-bar vertex is obtained and its solution to the process Z → bb-bar is applied. It is shown that it is possible to obtain a consistent description of both deviations, which is quite nontrivial because these effects are not simply correlated. The necessary value of the anomalous W interaction coupling, λ = -0.22 ± 0.01, is consistent with existing limitations and leads to definite predictions, e.g., for pair W production in e + e - collisions at LEP 200

  6. Mirror Symmetry Breaking in Helical Polysilanes: Preference between Left and Right of Chemical and Physical Origin

    Directory of Open Access Journals (Sweden)

    Michiya Fujiki

    2010-08-01

    Full Text Available From elemental particles to human beings, matter is dissymmetric with respect to mirror symmetry. In 1860, Pasteur conjectured that biomolecular handedness— homochirality—may originate from certain inherent dissymmetric forces existing in the universe. Kipping, a pioneer of organosilicon chemistry, was interested in the handedness of sodium chlorate during his early research life. Since Kipping first synthesized several Si-Si bonded oligomers bearing phenyl groups, Si-Si bonded high polymers carrying various organic groups—polysilanes—can be prepared by sodium-mediated condensation of the corresponding organodichlorosilanes. Among these polysilanes, optically active helical polysilanes with enantiomeric pairs of organic side groups may be used for testing the mirror symmetry-breaking hypothesis by weak neutral current (WNC origin in the realm of chemistry and material science. Several theoretical studies have predicted that WNC-existing chiral molecules with stereogenic centers and/or stereogenic bonds allow for distinguishing between image and mirror image molecules. Based on several amplification mechanisms, theorists claimed that minute differences, though still very subtle, may be detectable by precise spectroscopic and physicochemical measurements if proper chiral molecular pairs were employed. The present paper reports comprehensively an inequality between six pairs of helical polysilane high polymers, presumably, detectable by (chiroptical and achiral 29Si-/13C- NMR spectra, and viscometric measurements.

  7. Measurement of charge symmetry breaking in {ital np} elastic scattering at 350 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Abegg, R. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 (Canada); Berdoz, A.R.; Birchall, J.; Campbell, J.R. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Davis, C.A. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 (Canada)]|[University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Delheij, P.P.J. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 (Canada); Gan, L. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Green, P.W. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 (Canada)]|[University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Greeniaus, L.G. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Healey, D.C.; Helmer, R. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 (Canada); Kolb, N.; Korkmaz, E.; Lee, L. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Levy, C.D.P. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 (Canada); Li, J. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Miller, C.A. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 (Canada); Opper, A.K. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Page, S.A. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Postma, H. [Technische Hogeschool, Delft, The Netherlands, 2600 GA (Netherlands); Ramsay, W.D. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Soukup, J. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Stinson, G.M. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 (Canada)]|[University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); van Oers, W.T.H. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Zelenski, A.N. [TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 (Canada); Zhao, J. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada)

    1995-07-15

    TRIUMF Experiment 369, a measurement of charge symmetry breaking in {ital np} elastic scattering at 350 MeV, has completed data taking. Scattering asymmetries were measured with a polarized (unpolarized) neutron beam incident on an unpolarized (polarized) frozen spin target. Coincident scattered neutrons and recoil protons were detected by a mirror symmetric detection system in the center-of-mass angle range from 50{degree}--90{degree}. A preliminary result for the difference of the zero-crossing angles, where analyzing powers cross zero, is {Delta}{theta}{sub cm} =0.445{degree}{plus_minus}0.054{degree}(stat.){plus_minus}0.051{degree}(syst.) based on fits over the angle range 53.4{degree}{le}{theta}{sub cm}{le}86.9{degree}. The difference of the analyzing powers {Delta}{ital A}{equivalent_to}{ital A}{sub {ital n}}{minus}{ital A}{sub {ital p}}, where the subscripts denote polarized nucleons, was deduced with {ital dA}/{ital d}{theta}{sub cm}=({minus}1.35{plus_minus}0.05){times}10{sup {minus}2} deg{sup {minus}1} to be [60{plus_minus}7(stat.){plus_minus}7(syst.){plus_minus}2(syst.)] {times}10{sup {minus}4}.

  8. Charge symmetry breaking in the reaction np -> d pi sup 0

    CERN Document Server

    Opper, A K; Churchman, R M; Davis, C A; Finlay, R W; Green, P W; Greeniaus, L G; Hutcheon, D A; Jordan, D V; Korkmaz, E J; Niskanen, J A; O'Rielly, G V; Porcelli, T; Reitzner, S D; Walden, P L; Yen, S

    2000-01-01

    Charge Symmetry Breaking (CSB) in the strong interaction is due ultimately to the mass difference between the u and d quarks, but is described conveniently by meson-exchange models. TRIUMF experiment E704 measures the forward-backward asymmetry (A sub f sub b) in np->d pi sup 0 , which must be zero in the centre-of-mass if charge symmetry is conserved. The angle-integrated value of A sub f sub b is calculated to be -35x10 sup - sup 4 near 280 MeV with the dominant contribution coming from (pi sup 0 -eta) and (pi sup 0 -eta') mixing. The experiment uses a neutron beam of 279.5 MeV, a liquid hydrogen target, and the SASP spectrometer to detect deuterons from the np->d pi sup 0 reaction. A measurement of the pp->d pi sup + distribution, for which A sub f sub b must be zero, provides a strong test of systematic errors.

  9. Charge symmetry breaking in the reaction np {yields} d{pi}{sup 0}

    Energy Technology Data Exchange (ETDEWEB)

    Opper, A.K.; Auld, E.G.; Churchman, R.M.; Davis, C.A.; Finlay, R.W.; Green, P.W.; Greeniaus, L.G.; Hutcheon, D.A.; Jordan, D.V.; Korkmaz, E.J.; Niskanen, J.A.; O' Rielly, G.V.; Porcelli, T.; Reitzner, S.D.; Walden, P.L.; Yen, S

    2000-01-31

    Charge Symmetry Breaking (CSB) in the strong interaction is due ultimately to the mass difference between the u and d quarks, but is described conveniently by meson-exchange models. TRIUMF experiment E704 measures the foreward-backward asymmetry (A{sub fb}) in np{yields}d{pi}{sup 0}, which must be zero in the centre-of-mass if charge symmetry is conserved. The angle-integrated value of A{sub fb} is calculated to be -35x10{sup -4} near 280 MeV with the dominant contribution coming from ({pi}{sup 0}-{eta}) and ({pi}{sup 0}-{eta}') mixing. The experiment uses a neutron beam of 279.5 MeV, a liquid hydrogen target, and the SASP spectrometer to detect deuterons from the np{yields}d{pi}{sup 0} reaction. A measurement of the pp{yields}d{pi}{sup +} distribution, for which A{sub fb} must be zero, provides a strong test of systematic errors.

  10. Measurement of charge symmetry breaking in np elastic scattering at 350 MeV

    International Nuclear Information System (INIS)

    Abegg, R.; Berdoz, A.R.; Birchall, J.

    1994-10-01

    TRIUMF experiment 369, a measurement of charge symmetry breaking in np elastic scattering at 350 MeV, has completed data taking. Scattering asymmetries were measured with a polarized (unpolarized) neutron beam incident on an unpolarized (polarized) frozen spin target. Coincident scattered neutrons and recoil protons were detected by a mirror symmetric detection system in the center-of-mass angle range from 50 deg - 90 deg. A preliminary result for the difference of the zero-crossing angles, where analyzing powers cross zero, is Δθ cm = 0.445 deg ± 0.054 deg (stat.) ± 0.051 deg (syst.) based on fits over the angle range 53.4 deg ≤ θ cm ≤ 86.9 deg. The difference of the analyzing powers ΔA ≡ A n - A p , where the subscripts denote polarized nucleons, was deduced with dA/dθ cm = (-1.35 ± 0.05) x 10 -2 deg -1 to be [60 ± 7(stat.) ± 7(syst.) ± 2(syst.)] x 10 -4 . (author). 11 refs., 6 figs

  11. Symmetry breaking patterns of the 3-3-1 model at finite temperature

    Energy Technology Data Exchange (ETDEWEB)

    Borges, J.S. [Universidade do Estado do Rio de Janeiro, Departamento de Fisica de Altas Energias, Rio de Janeiro, RJ (Brazil); Ramos, Rudnei O. [Universidade do Estado do Rio de Janeiro, Departamento de Fisica Teorica, Rio de Janeiro, RJ (Brazil)

    2016-06-15

    We consider the minimal version of an extension of the standard electroweak model based on the SU(3){sub c} x SU(3){sub L} x U(1){sub X} gauge symmetry (the 3-3-1 model). We analyze the most general potential constructed from three scalars in the triplet representation of SU(3){sub L}, whose neutral components develop nonzero vacuum expectation values, giving mass for all the model's massive particles. For different choices of parameters, we obtain the particle spectrum for the two symmetry breaking scales: one where the SU(3){sub L} x U(1){sub X} group is broken down to SU(2){sub L} x U(1){sub Y} and a lower scale similar to the standard model one. Within the considerations used, we show that the model encodes two first-order phase transitions, respecting the pattern of symmetry restoration. The last transition, corresponding to the standard electroweak one, is found to be very weak first-order, most likely turning second-order or a crossover in practice. However, the first transition in this model can be strongly first-order, which might happen at a temperature not too high above the second one. We determine the respective critical temperatures for symmetry restoration for the model. (orig.)

  12. Vacuum structure and P T -symmetry breaking of the non-Hermetian (i ϕ3) theory

    Science.gov (United States)

    Shalaby, Abouzeid M.

    2017-07-01

    In this work, we study the P T -symmetric (i ϕ3 ) theory using the effective action formalism. To test the accuracy of the used technique, we apply it first to the P T -symmetric (-ϕ4 ) theory, where we reproduce the same results obtained in the literature using the method of Dyson-Schwinger equations. In 0 +1 space-time dimensions, the one-loop effective potential prediction for the (i ϕ3 ) theory ought to be more accurate than WKB results. The effective potential for the massless P T -symmetric (i ϕ3 ) model is shown to be bounded from below, which is the first analytic result that advocates the vacuum stability of this theory. Our calculations show that the massless theory possesses only one stable vacuum as in the literature, but for the massive theory we find that there exist two stable vacua. For a nonzero magnetic field, we show that the P T -symmetry of the theory is broken for negative imaginary magnetic field, which agrees with the Lee-Yang theorem. We argue that P T -symmetry breaking is a manifestation of the Yang-Lee edge singularity.

  13. Renormalization of the effective Lagrangian with spontaneous symmetry breaking: The SU(2) case

    International Nuclear Information System (INIS)

    Yan Qishu; Du Dongsheng

    2004-01-01

    We study the renormalization of the nonlinear effective SU(2) Lagrangian up to O(p 4 ) with spontaneous symmetry breaking. The Stueckelberg transformation, the background field gauge, the Schwinger proper time and heat kernel method, and the covariant short distance expansion technology guarantee gauge covariance and incorporate the Ward (Slavnov-Taylor) identities in the calculations. A modified power counting rule is introduced to consistently estimate and control the contributions of higher loops and higher-dimension operators. The one-loop renormalization group equations of the effective couplings are provided and analyzed. We find that the difference between the results obtained from the direct method and the renormalization group equation method can be quite large when the Higgs scalar boson is far below its decoupling limit. The exact one-loop calculation of d 1 in the renormalizable SU(2) Higgs model is provided to understand such a difference. A better way of calculating at the one-loop level in the framework of the effective theory method is suggested

  14. PT-symmetry breaking in complex nonlinear wave equations and their deformations

    International Nuclear Information System (INIS)

    Cavaglia, Andrea; Fring, Andreas; Bagchi, Bijan

    2011-01-01

    We investigate complex versions of the Korteweg-deVries equations and an Ito-type nonlinear system with two coupled nonlinear fields. We systematically construct rational, trigonometric/hyperbolic and elliptic solutions for these models including those which are physically feasible in an obvious sense, that is those with real energies, but also those with complex energy spectra. The reality of the energy is usually attributed to different realizations of an antilinear symmetry, as for instance PT-symmetry. It is shown that the symmetry can be spontaneously broken in two alternative ways either by specific choices of the domain or by manipulating the parameters in the solutions of the model, thus leading to complex energies. Surprisingly, the reality of the energies can be regained in some cases by a further breaking of the symmetry on the level of the Hamiltonian. In many examples, some of the fixed points in the complex solution for the field undergo a Hopf bifurcation in the PT-symmetry breaking process. By employing several different variants of the symmetries we propose many classes of new invariant extensions of these models and study their properties. The reduction of some of these models yields complex quantum mechanical models previously studied.

  15. Symmetry breaking, germ layer specification and axial organisation in aggregates of mouse embryonic stem cells.

    Science.gov (United States)

    van den Brink, Susanne C; Baillie-Johnson, Peter; Balayo, Tina; Hadjantonakis, Anna-Katerina; Nowotschin, Sonja; Turner, David A; Martinez Arias, Alfonso

    2014-11-01

    Mouse embryonic stem cells (mESCs) are clonal populations derived from preimplantation mouse embryos that can be propagated in vitro and, when placed into blastocysts, contribute to all tissues of the embryo and integrate into the normal morphogenetic processes, i.e. they are pluripotent. However, although they can be steered to differentiate in vitro into all cell types of the organism, they cannot organise themselves into structures that resemble embryos. When aggregated into embryoid bodies they develop disorganised masses of different cell types with little spatial coherence. An exception to this rule is the emergence of retinas and anterior cortex-like structures under minimal culture conditions. These structures emerge from the cultures without any axial organisation. Here, we report that small aggregates of mESCs, of about 300 cells, self-organise into polarised structures that exhibit collective behaviours reminiscent of those that cells exhibit in early mouse embryos, including symmetry breaking, axial organisation, germ layer specification and cell behaviour, as well as axis elongation. The responses are signal specific and uncouple processes that in the embryo are tightly associated, such as specification of the anteroposterior axis and anterior neural development, or endoderm specification and axial elongation. We discuss the meaning and implications of these observations and the potential uses of these structures which, because of their behaviour, we suggest to call 'gastruloids'. © 2014. Published by The Company of Biologists Ltd.

  16. Chiral symmetry breaking by spatial confinement in tactoidal droplets of lyotropic chromonic liquid crystals.

    Science.gov (United States)

    Tortora, Luana; Lavrentovich, Oleg D

    2011-03-29

    In many colloidal systems, an orientationally ordered nematic (N) phase emerges from the isotropic (I) melt in the form of spindle-like birefringent tactoids. In cases studied so far, the tactoids always reveal a mirror-symmetric nonchiral structure, sometimes even when the building units are chiral. We report on chiral symmetry breaking in the nematic tactoids formed in molecularly nonchiral polymer-crowded aqueous solutions of low-molecular weight disodium cromoglycate. The parity is broken by twisted packing of self-assembled molecular aggregates within the tactoids as manifested by the observed optical activity. Fluorescent confocal microscopy reveals that the chiral N tactoids are located at the boundaries of cells. We explain the chirality induction as a replacement of energetically costly splay packing of the aggregates within the curved bipolar tactoidal shape with twisted packing. The effect represents a simple pathway of macroscopic chirality induction in an organic system with no molecular chirality, as the only requirements are orientational order and curved shape of confinement.

  17. Mirror symmetry breaking of silicon polymers--from weak bosons to artificial helix.

    Science.gov (United States)

    Fujiki, Michiya

    2009-01-01

    From elemental particles to human beings, matter and living worlds in our universe are dissymmetric with respect to mirror symmetry. Since the early 19th century, the origin of biomolecular handedness has been puzzling scientists. Nature's elegant bottom-up preference, however, sheds light on new concepts of generating, amplifying, and switching artificial polymers, supramolecules, liquid crystals, and organic crystals that can exhibit ambidextrous circular dichroism in the UV/Visible region with efficiency in production under milder ambient conditions. In the 1920s, Kipping, who first synthesized polysilanes with phenyl groups, had much interest in the handedness of inorganic and organic substances from 1898 to 1909 in his early research life. Polysilanes--which are soluble Si-Si bonded chain-like near-UV chromophores that carry a rich variety of organic groups--may become a bridge between animate and inanimate polymer systems. The present account focuses on several mirror symmetry breaking phenomena exemplified in polysilanes carrying chiral and/or achiral side groups, which are in isotropic dilute solution, as polymer particles dispersed in solution, and in a double layer film immobilized at the solid surface, and subtle differences in the helix, by dictating ultimately ultraweak chiral forces at subatomic, atomic, and molecular levels. Copyright 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

  18. Some aspects of symmetry breaking in unified weak-electromagnetic gauge theories

    International Nuclear Information System (INIS)

    Lieberman, J.

    1974-01-01

    Some problems of symmetry breaking in unified weak-electromagnetic gauge theories are discussed. The scene is set with a brief history of weak interaction theory up until the impasse which led to the development of the unified weak-electromagnetic gauge theory strategy. The basic ideas underlying the new gauge strategy are described, illustrating how these ideas can be concretized in a specific model, and some of the prospects and problems which remain to be solved are discussed. A small contribution is made towards some of the problems which arise in applying the gauge strategy. Focus is particularly on the role of the Higgs scalars in the spontaneous breakdown of the theory. The following question is considered. How can one break the gauge symmetry in such a way that all of the weak vector mesons acquire mass but the photon remains massless. In the context of a specific model one studies the effects on calculable quantities, such as the proton-neutron mass difference, of varying the Higgs content, and investigates the appearance of pions as part of the Higgs system

  19. Discriminative phenomenological features of scale invariant models for electroweak symmetry breaking

    Directory of Open Access Journals (Sweden)

    Katsuya Hashino

    2016-01-01

    Full Text Available Classical scale invariance (CSI may be one of the solutions for the hierarchy problem. Realistic models for electroweak symmetry breaking based on CSI require extended scalar sectors without mass terms, and the electroweak symmetry is broken dynamically at the quantum level by the Coleman–Weinberg mechanism. We discuss discriminative features of these models. First, using the experimental value of the mass of the discovered Higgs boson h(125, we obtain an upper bound on the mass of the lightest additional scalar boson (≃543 GeV, which does not depend on its isospin and hypercharge. Second, a discriminative prediction on the Higgs-photon–photon coupling is given as a function of the number of charged scalar bosons, by which we can narrow down possible models using current and future data for the di-photon decay of h(125. Finally, for the triple Higgs boson coupling a large deviation (∼+70% from the SM prediction is universally predicted, which is independent of masses, quantum numbers and even the number of additional scalars. These models based on CSI can be well tested at LHC Run II and at future lepton colliders.

  20. Chiral symmetry breaking and surface faceting in chromonic liquid crystal droplets with giant elastic anisotropy.

    Science.gov (United States)

    Jeong, Joonwoo; Davidson, Zoey S; Collings, Peter J; Lubensky, Tom C; Yodh, A G

    2014-02-04

    Confined liquid crystals (LC) provide a unique platform for technological applications and for the study of LC properties, such as bulk elasticity, surface anchoring, and topological defects. In this work, lyotropic chromonic liquid crystals (LCLCs) are confined in spherical droplets, and their director configurations are investigated as a function of mesogen concentration using bright-field and polarized optical microscopy. Because of the unusually small twist elastic modulus of the nematic phase of LCLCs, droplets of this phase exhibit a twisted bipolar configuration with remarkably large chiral symmetry breaking. Further, the hexagonal ordering of columns and the resultant strong suppression of twist and splay but not bend deformation in the columnar phase, cause droplets of this phase to adopt a concentric director configuration around a central bend disclination line and, at sufficiently high mesogen concentration, to exhibit surface faceting. Observations of director configurations are consistent with Jones matrix calculations and are understood theoretically to be a result of the giant elastic anisotropy of LCLCs.

  1. Spontaneous symmetry breaking, and strings defects in hypercomplex gauge field theories

    Energy Technology Data Exchange (ETDEWEB)

    Cartas-Fuentevilla, R. [Universidad Autonoma de Puebla, Instituto de Fisica, Puebla, Pue. (Mexico); Meza-Aldama, O. [Universidad Autonoma de Puebla, Facultad de Ciencias Fisico-Matematicas, Puebla, Pue. (Mexico)

    2016-02-15

    Inspired by the appearance of split-complex structures in the dimensional reduction of string theory, and in the theories emerging as byproducts, we study the hypercomplex formulation of Abelian gauge field theories by incorporating a new complex unit to the usual complex one. The hypercomplex version of the traditional Mexican hat potential associated with the U(1) gauge field theory, corresponds to a hybrid potential with two real components, and with U(1) x SO(1,1) as symmetry group. Each component corresponds to a deformation of the hat potential, with the appearance of a new degenerate vacuum. Hypercomplex electrodynamics will show novel properties, such as spontaneous symmetry breaking scenarios with running masses for the vectorial and scalar Higgs fields, and such as Aharonov-Bohm type strings defects as exact solutions; these topological defects may be detected only by quantum interference of charged particles through gauge invariant loop integrals. In a particular limit, the hyperbolic electrodynamics does not admit topological defects associated with continuous symmetries. (orig.)

  2. A preliminary result of the second np charge symmetry breaking experiment at TRIUMF

    International Nuclear Information System (INIS)

    Zhao, J.; Abegg, R.; Berdoz, A.R.; Birchall, J.; Campbell, J.R.; Davis, C.A.; Delheij, P.P.J.; Gan, L.; Green, P.W.; Greeniaus, L.G.; Healey, D.C.; Helmer, R.; Kolb, N.; Korkmaz, E.a.; Lee, L.; Levy, C.D.P.; Li, J.; Miller, C.A.; Opper, A.K.; Page, S.A.; Postma, H.; Ramsay, W.D.; Soukup, J.; Stinson, G.M.; van Oers, W.T.H.; Zelenski, A.N.

    1995-01-01

    TRIUMF experiment 369, a measurement of charge symmetry breaking in np elastic scattering at 350 MeV, has completed data taking. Scattering asymmetries were measured with a polarized (unpolarized) neutron beam incident on an unpolarized (polarized) frozen spin target. Coincident scattered neutrons and recoil protons were detected by a mirror symmetric detection system in the center of mass angle range from 50 degree--90 degree. A preliminary result for the difference of the zero-crossing angles, where analyzing powers cross zero, is Δθ cm =0.48 degree ±0.08 degree(stat.)±0.08 degree(syst.) based on fits over the angle range 55.8 degree ≤θ cm ≤85.4 degree. The difference of the analyzing powers ΔA≡A n -A p , where the subscripts denote polarized nucleons, was deduced with dA/dθ cm =-1.47x10 -2 deg -1 from phase shift analyses to be [71±12(stat.)±12(syst.)]x10 -4 . It is expected that when all data are analyzed a statistical accuracy of about 7x10 -4 in ΔA will be achieved. copyright 1995 American Institute of Physics

  3. Symmetry-Breaking as a Paradigm to Design Highly-Sensitive Sensor Systems

    Directory of Open Access Journals (Sweden)

    Antonio Palacios

    2015-06-01

    Full Text Available A large class of dynamic sensors have nonlinear input-output characteristics, often corresponding to a bistable potential energy function that controls the evolution of the sensor dynamics. These sensors include magnetic field sensors, e.g., the simple fluxgate magnetometer and the superconducting quantum interference device (SQUID, ferroelectric sensors and mechanical sensors, e.g., acoustic transducers, made with piezoelectric materials. Recently, the possibilities offered by new technologies and materials in realizing miniaturized devices with improved performance have led to renewed interest in a new generation of inexpensive, compact and low-power fluxgate magnetometers and electric-field sensors. In this article, we review the analysis of an alternative approach: a symmetry-based design for highly-sensitive sensor systems. The design incorporates a network architecture that produces collective oscillations induced by the coupling topology, i.e., which sensors are coupled to each other. Under certain symmetry groups, the oscillations in the network emerge via an infinite-period bifurcation, so that at birth, they exhibit a very large period of oscillation. This characteristic renders the oscillatory wave highly sensitive to symmetry-breaking effects, thus leading to a new detection mechanism. Model equations and bifurcation analysis are discussed in great detail. Results from experimental works on networks of fluxgate magnetometers are also included.

  4. Holographic fermions at strong translational symmetry breaking: a Bianchi-VII case study

    Energy Technology Data Exchange (ETDEWEB)

    Bagrov, A. [Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, Nijmegen 6525 AJ (Netherlands); Kaplis, N.; Krikun, A.; Schalm, K.; Zaanen, J. [Institute Lorentz ITP, Leiden University, PO Box 9506, Leiden 2300 RA (Netherlands)

    2016-11-09

    It is presently unknown how strong lattice potentials influence the fermion spectral function of the holographic strange metals predicted by the AdS/CFT correspondence. This embodies a crucial test for the application of holography to condensed matter experiments. We show that for one particular momentum direction this spectrum can be computed for arbitrary strength of the effective translational symmetry breaking potential of the so-called Bianchi-VII geometry employing ordinary differential equations. Deep in the strange metal regime we find rather small changes to the single-fermion response computed by the emergent quantum critical IR, even when the potential becomes relevant in the infra-red. However, in the regime where holographic quasi-particles occur, defining a Fermi surface in the continuum, they acquire a finite lifetime at any finite potential strength. At the transition from irrelevancy to relevancy of the Bianchi potential in the deep infra-red the quasi-particle remnants disappear completely and the fermion spectrum exhibits a purely relaxational behaviour.

  5. Stability of effective thin-shell wormholes under Lorentz symmetry breaking supported by dark matter and dark energy

    Science.gov (United States)

    Övgün, Ali; Jusufi, Kimet

    2017-12-01

    In this paper, we construct generic, spherically symmetric thin-shell wormholes and check their stabilities using the unified dark sector, including dark energy and dark matter. We give a master equation, from which one can recover, as a special case, other stability solutions for generic spherically symmetric thin-shell wormholes. In this context, we consider a particular solution; namely we construct an effective thin-shell wormhole under Lorentz symmetry breaking. We explore stability analyses using different models of the modified Chaplygin gas with constraints from cosmological observations, such as seventh-year full Wilkinson microwave anisotropy probe data points, type Ia supernovae, and baryon acoustic oscillation. In all these models we find stable solutions by choosing suitable values for the parameters of the Lorentz symmetry breaking effect.

  6. Light-front quantized field theory (an introduction): spontaneous symmetry breaking. Phase transition in φ4 theory

    International Nuclear Information System (INIS)

    Srivastava, Prem P.

    1994-01-01

    The Dirac procedure is used to construct the Hamiltonian formulation of the scalar field theory on the light-front. The theory is quantized and the mechanism of the spontaneous symmetry breaking in the front form and the instant form dynamics are compared. The phase transition in (φ 4 )2 theory is also discussed and found to be of the second order. (author). 36 refs

  7. A ligand-conformation driving chiral generation and symmetry-breaking crystallization of a zinc(II) organoarsonate.

    Science.gov (United States)

    Zhou, Tian-Hua; Zhang, Jian; Zhang, Hai-Xia; Feng, Rui; Mao, Jiang-Gao

    2011-08-21

    An unusual ligand-conformation driving chiral generation and symmetry-breaking crystallization occurred simultaneously in the formation of a layered zinc(II) arsonate Zn(Hcapa)(4,4'-bipy) (1P) and its enantiomorph (1M) without any chiral sources, indicating that the asymmetrical crystallization of the coordination polymer from achiral precursors may be induced by the conformation control of the ligand. This journal is © The Royal Society of Chemistry 2011

  8. Academic Training Lectures | Theories of Electroweak Symmetry Breaking: A Post LHC Run-I Perspective | 26, 27 and 29 May

    CERN Multimedia

    2015-01-01

    Please note that our next series of Academic Training Lectures will take place on the 26, 27 and 29 May 2015.   Theories of Electroweak Symmetry Breaking: A Post LHC Run-I Perspective, by James Daniel Wells (University of Michigan (US)) from 11.00 a.m. to 12.00 p.m. in the Council Chamber (503-1-001) https://indico.cern.ch/event/383514/

  9. Determination of the Absolute Enantiomeric Excess of the Carbon Nanotube Ensemble by Symmetry Breaking Using the Optical Titration Method.

    Science.gov (United States)

    Sim, Jinsook; Kim, Somin; Jang, Myungsu; Park, Minsuk; Oh, Hyunkyu; Ju, Sang-Yong

    2017-10-17

    Symmetry breaking of single-walled carbon nanotubes (SWNTs) has profound effects on their optoelectronic properties that are essential for fundamental study and applications. Here, we show that isomeric SWNTs that exhibit identical photoluminescence (PL) undergo symmetry breaking by flavin mononucleotide (FMN) and exhibit dual PLs and different binding affinities (K a ). Increasing the FMN concentration leads to systematic PL shifts of SWNTs according to structural modality and handedness due to symmetry breaking. Density gradient ultracentrifugation using a FMN-SWNT dispersion displays PL shifts and different densities according to SWNT handedness. Using the optical titration method to determine the PL-based K a of SWNTs against an achiral surfactant as a titrant, left- and right-handed SWNTs display two-step PL inflection corresponding to respective K a values with FMN, which leads to the determination of the enantiomeric excess (ee) of the SWNT ensemble that was confirmed by circular dichroism measurement. Decreasing the FMN concentration for the SWNT dispersion leads to enantiomeric selection of SWNTs. The titration-based ee determination of the widely used sodium cholate-based SWNT dispersion was also demonstrated by using FMN as a cosurfactant.

  10. Symmetry-breaking analysis for the general Helmholtz-Duffing oscillator

    International Nuclear Information System (INIS)

    Cao Hongjun; Seoane, Jesus M.; Sanjuan, Miguel A.F.

    2007-01-01

    The symmetry breaking phenomenon for a general Helmholtz-Duffing oscillator as a function of a symmetric parameter in the nonlinear force is investigated. Different values of this parameter convert the general oscillator into either the Helmholtz or the Duffing oscillator. Due to the variation of the symmetric parameter, the phase space patterns of the unperturbed Helmholtz-Duffing oscillator will cause a huge difference between the left-hand homoclinic orbit and the right-hand one. In particular, the area of the left-hand homoclinic orbits is a strictly monotonously decreasing function, while the area of the right-hand homoclinic orbit varies only in a very small range. There exist distinct local supercritical and subcritical saddle-node bifurcations at two different centers. The left-hand and the right-hand existing regions of the harmonic solutions of the Helmholtz-Duffing oscillator created by the left-hand and the right-hand saddle-node bifurcation curves will lead to different transition in the amplitude-frequency plane. There exists also a critical frequency which has the effect that the left-hand homoclinic bifurcation value is equal to the right-hand homoclinic bifurcation value. And, if the amplitude coefficient of the Helmholtz-Duffing oscillator is used as the control parameter, and it is larger than the same left-hand and right-hand homoclinic bifurcation, then the global stability of the system will be destroyed at a lowest cost. Besides this critical frequency, the left-hand and the right-hand homoclinic bifurcations are not only unequal, but also their effects for the system's stability are different. Among them, the effect resulting from the small homoclinic bifurcation for the system's stability is local and negligible, while the effect from the large homoclinic bifurcation is global but this is accomplished at a quite larger cost

  11. Modeling finite-volume effects and chiral symmetry breaking in two-flavor QCD thermodynamics

    Science.gov (United States)

    Klein, Bertram

    2017-11-01

    Finite-volume effects in Quantum Chromodynamics (QCD) have been a subject of much theoretical interest for more than two decades. They are in particular important for the analysis and interpretation of QCD simulations on a finite, discrete space-time lattice. Most of these effects are closely related to the phenomenon of spontaneous breaking of the chiral flavor symmetry and the emergence of pions as light Goldstone bosons. These long-range fluctuations are strongly affected by putting the system into a finite box, and an analysis with different methods can be organized according to the interplay between pion mass and box size. The finite volume also affects critical behavior at the chiral phase transition in QCD. In the present review, I will be mainly concerned with modeling such finite volume effects as they affect the thermodynamics of the chiral phase transition for two quark flavors. I review recent work on the analysis of finite-volume effects which makes use of the quark-meson model for dynamical chiral symmetry breaking. To account for the effects of critical long-range fluctuations close to the phase transition, most of the calculations have been performed using non-perturbative Renormalization Group (RG) methods. I give an overview over the application of these methods to a finite volume. The method, the model and the results are put into the context of related work in random matrix theory for very small volumes, chiral perturbation theory for larger volumes, and related methods and approaches. They are applied towards the analysis of finite-volume effects in lattice QCD simulations and their interpretation, mainly in the context of the chiral phase transition for two quark flavors.

  12. A preliminary result of the second np charge symmetry breaking experiment at TRIUMF

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, J. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Abegg, R. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada); Berdoz, A.R.; Birchall, J.; Campbell, J.R. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Davis, C.A.; Delheij, P.P.J. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada); Gan, L. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Green, P.W.; Greeniaus, L.G. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Healey, D.C.; Helmer, R. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada); Kolb, N.; Korkmaz, E.a. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Lee, L. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Levy, C.D.P. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada); Li, J. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Miller, C.A. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada); Opper, A.K. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); Page, S.A. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Postma, H. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada); Ramsay, W.D. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Soukup, J.; Stinson, G.M. [University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada); van Oers, W.T.H. [University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Zelenski, A.N. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada)

    1995-07-10

    TRIUMF experiment 369, a measurement of charge symmetry breaking in np elastic scattering at 350 MeV, has completed data taking. Scattering asymmetries were measured with a polarized (unpolarized) neutron beam incident on an unpolarized (polarized) frozen spin target. Coincident scattered neutrons and recoil protons were detected by a mirror symmetric detection system in the center of mass angle range from 50{degree}--90{degree}. A preliminary result for the difference of the zero-crossing angles, where analyzing powers cross zero, is {Delta}{theta}{sub cm}=0.48{degree}{plus_minus}0.08{degree}({ital stat}.){plus_minus}0.08{degree}({ital syst}.) based on fits over the angle range 55.8{degree}{le}{theta}{sub cm}{le}85.4{degree}. The difference of the analyzing powers {Delta}{ital A}{equivalent_to}{ital A}{sub {ital n}}{minus}{ital A}{sub {ital p}}, where the subscripts denote polarized nucleons, was deduced with {ital dA}/{ital d}{theta}{sub cm}={minus}1.47{times}10{sup {minus}2} deg{sup {minus}1} from phase shift analyses to be [71{plus_minus}12({ital stat}.){plus_minus}12({ital syst}.)]{times}10{sup {minus}4}. It is expected that when all data are analyzed a statistical accuracy of about 7{times}10{sup {minus}4} in {Delta}{ital A} will be achieved. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  13. Entropic chiral symmetry breaking in self-organized two-dimensional colloidal crystals.

    Science.gov (United States)

    Mayoral, Kenny; Mason, Thomas G

    2014-07-07

    Long-range chiral symmetry breaking (CSB) has been recently observed in 2D self-organized rhombic crystals of hard, achiral, 72 degree rhombic microparticles. However, purely entropic selection of a CSB crystal in an idealized system of hard achiral shapes, in which attractions are entirely absent and the shape does not dictate a chiral tiling, has not yet been quantitatively predicted. Overcoming limitations of a purely rotational cage model, we investigate a translational-rotational cage model (TRCM) of dense systems of hard achiral rhombs and quantitatively demonstrate that entropy can spontaneously drive the preferential self-organization of a chiral crystal composed of achiral shapes that also tile into an achiral crystal. At different particle area fractions, ϕA, we calculate the number of accessible translational-rotational microstates, Ω, of a mobile central rhomb in a static cage of neighboring rhombs, which can have different orientation angles, γ, relative to the bisector of the crystalline axes. As we raise ϕA, two maxima emerge in Ω(γ) at non-zero cage orientation angles, ±γmax. These maxima correspond to additional translational microstates that become accessible in the CSB crystalline polymorph through reduced translational tip-tip interference. Thus, entropy, often associated with structural disorder, can drive CSB in condensed phase systems of non-attractive achiral objects that do not tile into chiral structures. The success of the TRCM in explaining the entropic origin of CSB in systems of hard rhombs indicates that the TRCM will have significant utility in predicting the self-organized behavior of dense systems of other hard shapes in 2D.

  14. Coexisting Kondo singlet state with antiferromagnetic long-range order: A possible ground state for Kondo insulators

    International Nuclear Information System (INIS)

    Zhang Guangming; Yu Lu

    2000-04-01

    The ground-state phase diagram of a half-filled anisotropic Kondo lattice model is calculated within a mean-field theory. For small transverse exchange coupling J perpendicular perpendicular c1 , the ground state shows an antiferromagnetic long-range order with finite staggered magnetizations of both localized spins and conduction electrons. When J perpendicular > J perpendicular c2 , the long-range order is destroyed and the system is in a disordered Kondo singlet state with a hybridization gap. Both ground states can describe the low-temperature phases of Kondo insulating compounds. Between these two distinct phases, there may be a coexistent regime as a result of the balance between local Kondo screening and magnetic interactions. (author)

  15. Proceedings of the 1992 workshops on high-energy physics with colliding beams. Volume 3, Electroweak symmetry breaking at colliding-beam facilities

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, J. [ed.

    1992-12-31

    This report contains viewgraphs on the following topics: Introduction to Electroweak Symmetry Breaking: Intermediate-Mass Higgs Bosons; Extended Higgs Sectors and Novel Searches; and Heavy Higgs Bosons and Strong WW Scattering.

  16. Fragile singlet ground-state magnetism in the pyrochlore osmates R2Os2O7 (R =Y and Ho)

    Science.gov (United States)

    Zhao, Z. Y.; Calder, S.; Aczel, A. A.; McGuire, M. A.; Sales, B. C.; Mandrus, D. G.; Chen, G.; Trivedi, N.; Zhou, H. D.; Yan, J.-Q.

    2016-04-01

    The singlet ground-state magnetism in pyrochlore osmates Y2Os2O7 and Ho2Os2O7 is studied by dc and ac susceptibility, specific heat, and neutron powder diffraction measurements. Despite the expected nonmagnetic singlet in the strong spin-orbit coupling (SOC) limit for Os4 + (5 d4 ), Y2Os2O7 exhibits a spin-glass ground state below 4 K with weak magnetism, suggesting possible proximity to a quantum phase transition between the nonmagnetic state in the strong SOC limit and a magnetic state in the strong superexchange limit. Ho2Os2O7 has the same structural distortion as in Y2Os2O7 ; however, the Os sublattice in Ho2Os2O7 shows long-range magnetic ordering below 36 K. The sharp difference of the magnetic ground state between Y2Os2O7 and Ho2Os2O7 signals that the singlet ground-state magnetism in R2Os2O7 is fragile and can be disturbed by the weak 4 f -5 d interactions.

  17. Optical probes of symmetry breaking in magnetic and superconducting BaFe2(As1-xPx)2

    Science.gov (United States)

    Orenstein, Joseph

    The discovery of iron pnictide superconductors has opened promising new directions in the effort to fully understand the phenomenon of high-Tc, with a focus on the connections between superconductivity, magnetism, and electronic nematicity. The BaFe2(As1-xPx)2 (P:Ba122) system in particular has received attention because isovalent substitution of As for P generates less disorder than doping on the Fe site. The phase diagram of P:Ba122 is characterized by a line of simultaneous antiferromagnetic (AF) and tetragonal-to-orthorhombic transitions, Ts (x) , that penetrates the superconducting dome at x =0.28, just below optimal doping (xopt = 0.30). In this work, we use spatially-resolved optical polarimetry and photomodulated reflectance to detect linear birefringence and therefore breaking of 4-fold rotational (C4) symmetry. In underdoped (xTsand grows continuously with decreasing T . The birefringence is unidirectional in a large (300 μm x300 μm) field of view, suggesting that C4 breaking in this range of T is caused by residual strain that couples to a diverging nematic susceptibility. Birefringence maps just below Ts (x) show the appearance of domains, indicating the onset of spontaneous symmetry breaking to an AF ground state. Surprisingly, in samples with x>0.28, in which the low T phase is superconducting/ tetragonal rather than AF/orthorhombic, C4 breaking is observed as well, with an abrupt onset and domain formation at 55 K. We tentatively associate these features with a transition to an AF phase induced by residual strain, as previously proposed [H.-H. Kuo et al. Phys. Rev. B86, 134507 (2012)] to account for structure in resistivity vs. T. Time-resolved photomodulation allow us to follow the amplitude of the AF order with time following pulsed photoexcitation. Below Tc the AF order at first weakens , but then strengthens in response to the photoinduced weakening of superconductivity. This complex time evolution is accounted for quantitatively by a model

  18. The off-shell nucleon-nucleon interaction in the singlet s-state

    International Nuclear Information System (INIS)

    Groot, H. de

    1975-01-01

    This thesis studies the off-shell behaviour of the neutron-proton interaction in the singlet state. To generate phase-shift-equivalent potentials a particular type of inversion problem is solved. It requires the potential to contain a non-local, separable part which is supposed to describe part of the short-range interaction. A special solution of the general inversion problem that produces potentials consisting of two separable terms is studied. Criteria to accept or reject particular inversion solutions are discussed. Neutron-proton potentials in the 1 S 0 partial wave which form part of the input for the general inversion procedure are defined. Different local potential tails are chosen, as well as varying short-range interactions, both local and non-local. The input phase shifts are discussed including three extrapolations of the phase shifts at high energy. The half-shell transition matrix for the potentials defined is studied. Some problems introduced by the additional electromagnetic interaction in the proton-proton system is investigated. (Auth.)

  19. Tb3+ in TbCo3B2, a Singlet Ground State System, Studied by Inelastic Neutron Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Rivin, Oleg [Nuclear Research Centre-Negev, Israel; and Ben-Gurion University, Israel; Osborn, Raymond [Argonne National Laboratory (ANL); Kolesnikov, Alexander I [ORNL; Caspi, El' ad N. [Nuclear Research Centre-Negev, Israel; Shaked, Hagai [Ben Gurion University of the Negev

    2008-01-01

    The results of inelastic neutron scattering on the hexagonal compounds TbCo3B2 and Tb0.75Y0.25Co3B2, at several temperatures are reported. The crystal field level scheme of Tb3+ ions in the paramagnetic phase is determined. This scheme contains a non-magnetic singlet (G1) as ground state. Inelastic neutron scattering at low temperature (10 K), leads to a different energy level scheme, where the singlet ground state is ferromagnetic with # 0. This is a "self induced" ferromagnetism on the Tb sub-lattice, resulting from the admixture of higher crystal field levels into the singlet ground state by the exchange field. The resulting magnitudes of these ground state magnetic moments are 5.6(3) and 3(1) muB for TbCo3B2 and Tb0.75Y0.25Co3B2, respectively. These values are much smaller than the free ion value of 9 muB and are in agreement with previously observed values. Such large reductions are characteristic of the "self induced" ferromagnetism. The temperature dependence of the magnetic moment, magnetic anisotropy, Tb sub-lattice dilution and magnetic susceptibility are discussed.

  20. Extraction of the strong neutron-proton mass difference from the charge symmetry breaking in pn->dpi{sup 0}

    Energy Technology Data Exchange (ETDEWEB)

    Filin, A.; Baru, V. [Institut fuer Kernphysik (Theorie) and Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Institute for Theoretical and Experimental Physics, 117218, B. Cheremushkinskaya 25, Moscow (Russian Federation); Epelbaum, E. [Institut fuer Kernphysik (Theorie) and Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universitaet Bonn, D-53115 Bonn (Germany); Haidenbauer, J., E-mail: j.haidenbauer@fz-juelich.d [Institut fuer Kernphysik (Theorie) and Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich (Germany); Hanhart, C. [Institut fuer Kernphysik (Theorie) and Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich (Germany); Kudryavtsev, A. [Institute for Theoretical and Experimental Physics, 117218, B. Cheremushkinskaya 25, Moscow (Russian Federation); Meissner, U.-G. [Institut fuer Kernphysik (Theorie) and Juelich Center for Hadron Physics, Forschungszentrum Juelich, D-52425 Juelich (Germany); Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universitaet Bonn, D-53115 Bonn (Germany); Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich (Germany)

    2009-11-16

    We perform a complete calculation of charge symmetry breaking effects for the reaction pn->dpi{sup 0} at leading order in chiral perturbation theory. A new leading-order operator is included. From our analysis we extract deltam{sub N}{sup str}, the strong contribution to the neutron-proton mass difference. The value obtained, deltam{sub N}{sup str}=(1.5+-0.8 (exp.)+-0.5 (th.)) MeV, is consistent with the result based on the Cottingham sum rule. This agreement provides a non-trivial test of our current understanding of the chiral structure of QCD.

  1. Relativistic Anandan quantum phase and the Aharonov–Casher effect under Lorentz symmetry breaking effects in the cosmic string spacetime

    Energy Technology Data Exchange (ETDEWEB)

    Bakke, K., E-mail: kbakke@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900, João Pessoa-PB (Brazil); Furtado, C., E-mail: furtado@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900, João Pessoa-PB (Brazil); Belich, H., E-mail: belichjr@gmail.com [Departamento de Física e Química, Universidade Federal do Espírito Santo, Av. Fernando Ferrari, 514, Goiabeiras, 29060-900, Vitória, ES (Brazil)

    2016-09-15

    From the modified Maxwell theory coupled to gravity, we establish a possible scenario of the violation of the Lorentz symmetry and write an effective metric for the cosmic string spacetime. Then, we investigate the arising of an analogue of the Anandan quantum phase for a relativistic Dirac neutral particle with a permanent magnetic dipole moment in the cosmic string spacetime under Lorentz symmetry breaking effects. Besides, we analyse the influence of the effects of the Lorentz symmetry violation and the topology of the defect on the Aharonov–Casher geometric quantum phase in the nonrelativistic limit.

  2. Vibronic singlet and triplet steady-state interplay emissions in phenazine-based 1,2,3-triazole films

    Science.gov (United States)

    Costa, Bárbara B. A.; Souza, Paula D. C.; Gontijo, Rafael N.; Jardim, Guilherme A. M.; Moreira, Roberto L.; da Silva, Eufrânio N.; Cury, Luiz A.

    2018-03-01

    Photoluminescence and phosphorescence emissions of solid-state phenazine films were investigated in steady-state experimental conditions. Important discrepancies were observed for blended films where a host optically inert matrix was introduced to disperse the probe molecules. A vibronic spin-orbit phosphorescent emission clearly appeared, while for the films solely composed by the probe molecules, the phosphorescence broadened and presented a structureless shape, shifted to longer wavelengths. Further Arrhenius behavior analysis on the photoluminescent and phosphorescent emissions on temperature, corroborated the direct and reverse intersystem crossing interplay between singlet and triplet states. Molecular aggregation is responsible for the deterioration of non-blended triazole films phosphorescence.

  3. Toward Designed Singlet Fission: Electronic States and Photophysics of 1,3-Diphenylisobenzofuran

    Czech Academy of Sciences Publication Activity Database

    Schwerin, A. F.; Johnson, J. C.; Smith, M. B.; Sreearunothai, P.; Popovič, D.; Černý, Jiří; Havlas, Zdeněk; Paci, I.; Akdag, A.; MacLeod, M. K.; Chen, X.; David, D. E.; Ratner, M. A.; Miller, J. R.; Nozik, A. J.; Michl, Josef

    2010-01-01

    Roč. 114, č. 3 (2010), s. 1457-1473 ISSN 1089-5639 R&D Projects: GA MŠk ME09114 Grant - others:NSF(US) OISE-0532040 Institutional research plan: CEZ:AV0Z40550506 Keywords : photophysics * singlet fission * DFT Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.732, year: 2010

  4. Epithelial rotation is preceded by planar symmetry breaking of actomyosin and protects epithelial tissue from cell deformations.

    Directory of Open Access Journals (Sweden)

    Ivana Viktorinová

    2017-11-01

    Full Text Available Symmetry breaking is involved in many developmental processes that form bodies and organs. One of them is the epithelial rotation of developing tubular and acinar organs. However, how epithelial cells move, how they break symmetry to define their common direction, and what function rotational epithelial motions have remains elusive. Here, we identify a dynamic actomyosin network that breaks symmetry at the basal surface of the Drosophila follicle epithelium of acinar-like primitive organs, called egg chambers, and may represent a candidate force-generation mechanism that underlies the unidirectional motion of this epithelial tissue. We provide evidence that the atypical cadherin Fat2, a key planar cell polarity regulator in Drosophila oogenesis, directs and orchestrates transmission of the intracellular actomyosin asymmetry cue onto a tissue plane in order to break planar actomyosin symmetry, facilitate epithelial rotation in the opposite direction, and direct the elongation of follicle cells. In contrast, loss of this rotational motion results in anisotropic non-muscle Myosin II pulses that are disorganized in plane and causes cell deformations in the epithelial tissue of Drosophila eggs. Our work demonstrates that atypical cadherins play an important role in the control of symmetry breaking of cellular mechanics in order to facilitate tissue motion and model epithelial tissue. We propose that their functions may be evolutionarily conserved in tubular/acinar vertebrate organs.

  5. Loop models on random maps via nested loops: the case of domain symmetry breaking and application to the Potts model

    Science.gov (United States)

    Borot, G.; Bouttier, J.; Guitter, E.

    2012-12-01

    We use the nested loop approach to investigate loop models on random planar maps where the domains delimited by the loops are given two alternating colors, which can be assigned different local weights, hence allowing for an explicit Z2 domain symmetry breaking. Each loop receives a non-local weight n, as well as a local bending energy which controls loop turns. By a standard cluster construction that we review, the Q = n2 Potts model on general random maps is mapped to a particular instance of this problem with domain-non-symmetric weights. We derive in full generality a set of coupled functional relations for a pair of generating series which encode the enumeration of loop configurations on maps with a boundary of a given color, and solve it by extending well-known complex analytic techniques. In the case where loops are fully packed, we analyze in detail the phase diagram of the model and derive exact equations for the position of its non-generic critical points. In particular, we underline that the critical Potts model on general random maps is not self-dual whenever Q ≠ 1. In a model with domain-symmetric weights, we also show the possibility of a spontaneous domain symmetry breaking driven by the bending energy. This article is part of ‘Lattice models and integrability’, a special issue of Journal of Physics A: Mathematical and Theoretical in honour of F Y Wu's 80th birthday.

  6. Epithelial rotation is preceded by planar symmetry breaking of actomyosin and protects epithelial tissue from cell deformations.

    Science.gov (United States)

    Viktorinová, Ivana; Henry, Ian; Tomancak, Pavel

    2017-11-01

    Symmetry breaking is involved in many developmental processes that form bodies and organs. One of them is the epithelial rotation of developing tubular and acinar organs. However, how epithelial cells move, how they break symmetry to define their common direction, and what function rotational epithelial motions have remains elusive. Here, we identify a dynamic actomyosin network that breaks symmetry at the basal surface of the Drosophila follicle epithelium of acinar-like primitive organs, called egg chambers, and may represent a candidate force-generation mechanism that underlies the unidirectional motion of this epithelial tissue. We provide evidence that the atypical cadherin Fat2, a key planar cell polarity regulator in Drosophila oogenesis, directs and orchestrates transmission of the intracellular actomyosin asymmetry cue onto a tissue plane in order to break planar actomyosin symmetry, facilitate epithelial rotation in the opposite direction, and direct the elongation of follicle cells. In contrast, loss of this rotational motion results in anisotropic non-muscle Myosin II pulses that are disorganized in plane and causes cell deformations in the epithelial tissue of Drosophila eggs. Our work demonstrates that atypical cadherins play an important role in the control of symmetry breaking of cellular mechanics in order to facilitate tissue motion and model epithelial tissue. We propose that their functions may be evolutionarily conserved in tubular/acinar vertebrate organs.

  7. Flavour symmetry breaking and tuning the strange quark mass for 2+1 quark flavours

    Energy Technology Data Exchange (ETDEWEB)

    Bietenholz, W. [Universidad Autonoma de Mexico (Mexico). Inst. de Ciencias Nucleares; Bornyakov, V. [Institute for High Energy Physics, Protovino (Russian Federation); Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Goeckeler, M. [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)

    2010-12-15

    QCD lattice simulations with 2+1 flavours typically start at rather large up-down and strange quark masses and extrapolate first the strange quark mass to its physical value and then the updown quark mass. An alternative method of tuning the quark masses is discussed here in which the singlet quark mass is kept fixed, which ensures that the kaon always has mass less than the physical kaon mass. Using group theory the possible quark mass polynomials for a Taylor expansion about the flavour symmetric line are found, which enables highly constrained fits to be used in the extrapolation of hadrons to the physical pion mass. Numerical results confirm the usefulness of this expansion and an extrapolation to the physical pion mass gives hadron mass values to within a few percent of their experimental values. (orig.)

  8. Nuclear magnetic resonance in high magnetic fields: Study of singlet-ground-state due to 1-D quantum spin effect

    Science.gov (United States)

    Chiba, Meiro; Ajiro, Yoshitami; Satoh, Eiji; Kubo, Takeji

    1996-02-01

    In one-dimensional (1-D) magnets the singlet-ground-state (SGS) due to the quantum spin effect is one of the most interesting phenomena. The temperature and the field dependences of the proton spin-lattice relaxation under magnetic fields up to 15 T have been observed for SGS materials, namely, NENP (Haldane system) and CuCI 2(γ-picoline) 2 (alternating antiferromagnetic chain). The results clearly show the excitation of SGS with a characteristic energy gap in the magnetic excited state. The observed relaxation rate is discussed in terms of the number of magnetic excitons in focussing on the dissimilarity between two systems.

  9. Singlet Fission

    Czech Academy of Sciences Publication Activity Database

    Smith, M. B.; Michl, Josef

    2010-01-01

    Roč. 110, č. 11 (2010), s. 6891-6936 ISSN 0009-2665 Grant - others:Department of Energy(US) DE- FG36 -08GO18017 Institutional research plan: CEZ:AV0Z40550506 Keywords : solar energy conversion * photovoltaics * singlet fission Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 33.033, year: 2010

  10. Hartee Fock Symmetry Breaking Effects in La2CuO4: Hints for connecting the Mott and Slater Pictures and Pseudogap Prediction

    Directory of Open Access Journals (Sweden)

    Alejandro Cabo Montes de Oca

    2010-03-01

    Full Text Available This work expands the results and derivations presented in a recent letter. It is argued that symmetry breaking Hartree-Fock (HF solutions of a simple model of the Cu-O planes in La2CuO4, are able to describe the insulator and antiferromagnetic characters of this material. Then, this classical primer of a Mott insulator is alternatively obtained here as an exact Slater insulator within the simplest of the first principles schemes. Moreover, pseudogap HF states are also predicted. The maximal energy gap of 100 meV over the Fermi surface of this wavefunction, reasonably well matches the ARPES upper pseudogap measurements for La2CuO4 in the zero doping limit. These surprising results followed after eliminating spin and crystal symmetry constraints usually imposed on the HF orbitals. The discussion helps to clarify the role of the antiferromagnetism and pseudogaps in the physics of the HTSC materials and indicates a promising way to start conciliating the Mott and Slater pictures for the description of the transition metal oxides.

  11. On the harmonic-type and linear-type confinement of a relativistic scalar particle yielded by Lorentz symmetry breaking effects

    Energy Technology Data Exchange (ETDEWEB)

    Bakke, K., E-mail: kbakke@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900, João Pessoa-PB (Brazil); Belich, H., E-mail: belichjr@gmail.com [Departamento de Física e Química, Universidade Federal do Espírito Santo, Av. Fernando Ferrari, 514, Goiabeiras, 29060-900, Vitória, ES (Brazil)

    2016-10-15

    Based on the Standard Model Extension, we investigate relativistic quantum effects on a scalar particle in backgrounds of the Lorentz symmetry violation defined by a tensor field. We show that harmonic-type and linear-type confining potentials can stem from Lorentz symmetry breaking effects, and thus, relativistic bound state solutions can be achieved. We first analyse a possible scenario of the violation of the Lorentz symmetry that gives rise to a harmonic-type potential. In the following, we analyse another possible scenario of the breaking of the Lorentz symmetry that induces both harmonic-type and linear-type confining potentials. In this second case, we also show that not all values of the parameter associated with the intensity of the electric field are permitted in the search for polynomial solutions to the radial equation, where the possible values of this parameter are determined by the quantum numbers of the system and the parameters associated with the violation of the Lorentz symmetry.

  12. β decay of (38)Ca: sensitive test of isospin symmetry-breaking corrections from mirror superallowed 0+ → 0+ transitions.

    Science.gov (United States)

    Park, H I; Hardy, J C; Iacob, V E; Bencomo, M; Chen, L; Horvat, V; Nica, N; Roeder, B T; Simmons, E; Tribble, R E; Towner, I S

    2014-03-14

    We report the first branching-ratio measurement of the superallowed 0+→0+β transition from Ca38. The result, 0.7728(16), leads to an ft value of 3062.3(68) s with a relative precision of ±0.2%. This makes possible a high-precision comparison of the ft values for the mirror superallowed transitions, Ca38→38mK and K38m→Ar38, which sensitively tests the isospin symmetry-breaking corrections required to extract Vud, the up-down quark-mixing element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, from superallowed β decay. The result supports the corrections currently used and points the way to even tighter constraints on CKM unitarity.

  13. Methods to introduce sub-micrometer, symmetry-breaking surface corrugation to silicon substrates to increase light trapping

    Energy Technology Data Exchange (ETDEWEB)

    Han, Sang Eon; Hoard, Brittany R.; Han, Sang M.; Ghosh, Swapnadip

    2018-04-10

    Provided is a method for fabricating a nanopatterned surface. The method includes forming a mask on a substrate, patterning the substrate to include a plurality of symmetry-breaking surface corrugations, and removing the mask. The mask includes a pattern defined by mask material portions that cover first surface portions of the substrate and a plurality of mask space portions that expose second surface portions of the substrate, wherein the plurality of mask space portions are arranged in a lattice arrangement having a row and column, and the row is not oriented parallel to a [110] direction of the substrate. The patterning the substrate includes anisotropically removing portions of the substrate exposed by the plurality of spaces.

  14. Electronic in-plane symmetry breaking at field-tuned quantum criticality in CeRhIn5

    Energy Technology Data Exchange (ETDEWEB)

    Helm, T. [MPI-CPFS (Germany); Bachmann, M. [MPI-CPFS (Germany); Moll, P.J.W. [MPI-CPFS (Germany); Balicas, L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab. (MagLab); Chan, Mun Keat [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ramshaw, Brad [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mcdonald, Ross David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Balakirev, Fedor Fedorovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bauer, Eric Dietzgen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ronning, Filip [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-23

    Electronic nematicity appears in proximity to unconventional high-temperature superconductivity in the cuprates and iron-arsenides, yet whether they cooperate or compete is widely discussed. While many parallels are drawn between high-Tc and heavy fermion superconductors, electronic nematicity was not believed to be an important aspect in their superconductivity. We have found evidence for a field-induced strong electronic in-plane symmetry breaking in the tetragonal heavy fermion superconductor CeRhIn5. At ambient pressure and zero field, it hosts an anti-ferromagnetic order (AFM) of nominally localized 4f electrons at TN=3.8K(1). Moderate pressure of 17kBar suppresses the AFM order and a dome of superconductivity appears around the quantum critical point. Similarly, a density-wave-like correlated phase appears centered around the field-induced AFM quantum critical point. In this phase, we have now observed electronic nematic behavior.

  15. Follow your gut: relaying information from the site of left-right symmetry breaking in the mouse.

    Science.gov (United States)

    Saijoh, Yukio; Viotti, Manuel; Hadjantonakis, Anna-Katerina

    2014-06-01

    A central unresolved question in the molecular cascade that drives establishment of left-right (LR) asymmetry in vertebrates are the mechanisms deployed to relay information between the midline site of symmetry-breaking and the tissues which will execute a program of asymmetric morphogenesis. The cells located between these two distant locations must provide the medium for signal relay. Of these, the gut endoderm is an attractive candidate tissue for signal transmission since it comprises the epithelium that lies between the node, where asymmetry originates, and the lateral plate, where asymmetry can first be detected. Here, focusing on the mouse as a model, we review our current understanding and entertain open questions concerning the relay of LR information from its origin. © 2014 Wiley Periodicals, Inc.

  16. Nonequilibrium dielectric noise in solids in the presence of modulation of electrical permittivity and spectral symmetry breaking under feedback

    Science.gov (United States)

    Sinha, Dhiraj; Bouffanais, Roland; Huang, Shao Ying

    2017-11-01

    We present an analytical study on the generation of broadband electromagnetic noise in solids as a consequence of variations in the dielectric constant under the impact of polarization induced by nonequilibrium thermodynamic fluctuations. The analysis leads to a specific formulation of the fluctuation dissipation theorem in the context of dielectric materials having finite electrodynamic boundary conditions, which drive energy into the system, under feedback, during its under interaction with a heat bath. The ensuing spectral symmetry breaking of the broadband noise yields bursts of narrowband signals, which can potentially result in phase transitions and dielectric breakdown. This study sheds a new light on high temperature precision calorimetry, while also improving our understanding of unexpected breakdowns in devices like CMOS components, capacitors and batteries.

  17. Symmetry-Breaking for Formation of Rectangular CdSe Two-Dimensional Nanocrystals in Zinc-Blende Structure.

    Science.gov (United States)

    Chen, Yiya; Chen, Dongdong; Li, Zheng; Peng, Xiaogang

    2017-07-26

    Formation of CdSe nanocrystals with two-dimensional quantum confinement (CdSe 2D nanocrystals) was studied with preformed CdSe nanocrystals in the size range between 1.7 and 2.2 nm as seeds. Specifically, the 2D CdSe nanocrystals were encased with six {100} facets of the zinc-blende (face-center-cubic) structure, that is, 1.5 nm in thickness with quite large atomically flat {100} basal planes (∼8 nm width and X ≈ 45 nm length). Symmetry breaking between the thickness and lateral directions occurred in the early stage by rapid formation of single-dot intermediates with flat yet polar {100} basal planes and the desired thickness from the seeds through intraparticle ripening. Two single-dot intermediates fused together through their reactive side facets-mostly the nonpolar {110} ones-to form 2D embryos with the same thickness. Such oriented attachment continued selectively onto the reactive side facets of the 2D embryos. Simultaneously, intraparticle ripening occurred slowly on the side facets of the 2D nanocrystals, which converted unstable side facets gradually to four stable {100} ones. When ∼3 stable {100} side facets were developed, oriented attachment would continue on the remaining active one, which would result in the second symmetry breaking between two lateral directions. Cadmium acetate assisted both formation of single-dot intermediates and oriented attachment. Cadmium alkanoates with a long hydrocarbon chain selectively stabilized polar {100} facets on the nanocrystals including single-dot intermediates and shuttled insoluble acetate to the reactive surface of the nanocrystals.

  18. Equal-Spin Andreev Reflection on Junctions of Spin-Resolved Quantum Hall Bulk State and Spin-Singlet Superconductor.

    Science.gov (United States)

    Matsuo, Sadashige; Ueda, Kento; Baba, Shoji; Kamata, Hiroshi; Tateno, Mizuki; Shabani, Javad; Palmstrøm, Christopher J; Tarucha, Seigo

    2018-02-22

    The recent development of superconducting spintronics has revealed the spin-triplet superconducting proximity effect from a spin-singlet superconductor into a spin-polarized normal metal. In addition recently superconducting junctions using semiconductors are in demand for highly controlled experiments to engineer topological superconductivity. Here we report experimental observation of Andreev reflection in junctions of spin-resolved quantum Hall (QH) states in an InAs quantum well and the spin-singlet superconductor NbTi. The measured conductance indicates a sub-gap feature and two peaks on the outer side of the sub-gap feature in the QH plateau-transition regime increases. The observed structures can be explained by considering transport with Andreev reflection from two channels, one originating from equal-spin Andreev reflection intermediated by spin-flip processes and second arising from normal Andreev reflection. This result indicates the possibility to induce the superconducting proximity gap in the the QH bulk state, and the possibility for the development of superconducting spintronics in semiconductor devices.

  19. Efficiencies of singlet oxygen production and rate constants for oxygen quenching in the S1 state of dicyanonaphthalenes and related compounds.

    Science.gov (United States)

    Tanaka, Fujio; Tsumura, Kazuyuki; Furuta, Tomoaki; Iwamoto, Kenichi; Okamoto, Masami

    2008-01-01

    The quantum yield of singlet oxygen ((1)O(2) ((1)Delta(g))) production (Phi(Delta)) in the oxygen quenching of photoexcited states for 1,2-dicyanonaphthalene (1,2-DCNN), 1,4-dicyanonaphthalene (1,4-DCNN) and 2,3-dicyanonaphthalene (2,3-DCNN) in cyclohexane, benzene, and acetonitrile was measured using a time-resolved thermal lens (TRTL) technique, in order to determine the efficiency of singlet oxygen ((1)Delta(g)) production in the first excited singlet state (S(1)), (f(Delta)(S)). The efficiencies of singlet oxygen ((1)Delta(g)) production from the lowest triplet state (T(1)), (f(Delta)(T)), were nearly unity for all DCNNs in all the solvents. The values of f(Delta)(S) were fairly large for 1,2-DCNN (0.33-0.57) and 1,4-DCNN (0.33-0.66), but were close to zero for 2,3-DCNN. Rate constants for oxygen quenching in the S(1) state (k(q)(S)) obtained for these compounds were significantly smaller than diffusion-controlled rate constants. The kinetics for processes leading to production and no production of singlet oxygen is discussed on the basis of the values of f(Delta)(S) and k(q)(S). The results obtained regarding phenanthrene (PH), 9-cyanophenanthrene (9-CNPH), pyrene (PY) and 1-cyanopyrene (1-CNPY) are also discussed.

  20. Theory of singlet-ground-state magnetism. Application to field-induced transitions in CsFeCl3 and CsFeBr3

    DEFF Research Database (Denmark)

    Lindgård, P.-A.; Schmid, B.

    1993-01-01

    In the singlet ground-state systems CsFeCl3 and CsFeBr3 a large single-ion anisotropy causes a singlet ground state and a doubly degenerate doublet as the first excited states of the Fe2+ ion. In addition the magneteic interaction is anisotropic being much larger along the z axis than perpendicular...... to it. Therefore, these quasi-one-dimensional magnetic model systems are ideal to demonstrate unique correlation effects. Within the framework of the correlation theory we derive the expressions for the excitation spectrum. When a magnetic field is applied parallel to the z axis both substances have...

  1. Abrupt two-step and symmetry breaking spin crossover in an iron(III) complex: an exceptionally wide [LS-HS] plateau.

    Science.gov (United States)

    Harding, David J; Phonsri, Wasinee; Harding, Phimphaka; Murray, Keith S; Moubaraki, Boujemaa; Jameson, Guy N L

    2015-09-14

    [Fe(qsal-Br)2]NO3·2MeOH is reported which undergoes abrupt two step symmetry breaking spin crossover, T½(1st step) = 136 K and T½(2nd step) = 232 K with a hysteresis of 16 K and 5 K, respectively, and an unprecedented [HS-LS] plateau of 96 K.

  2. Search for Singlet Fission Chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Havlas, Z.; Akdag, A.; Smith, M. B.; Dron, P.; Johnson, J. C.; Nozik, A. J.; Michl, J.

    2012-01-01

    Singlet fission, in which a singlet excited chromophore shares its energy with a ground-state neighbor and both end up in their triplet states, is of potential interest for solar cells. Only a handful of compounds, mostly alternant hydrocarbons, are known to perform efficiently. In view of the large number of conditions that a successful candidate for a practical cell has to meet, it appears desirable to extend the present list of high performers to additional classes of compounds. We have (i) identified design rules for new singlet fission chromophores and for their coupling to covalent dimers, (ii) synthesized them, and (iii) evaluated their performance as neat solids or covalent dimers.

  3. Zethrene biradicals: How pro-aromaticity is expressed in the ground electronic state and in the lowest energy singlet, triplet, and ionic states

    Science.gov (United States)

    Zafra, José Luis; González Cano, Rafael C.; Ruiz Delgado, M. Carmen; Sun, Zhe; Li, Yuan; López Navarrete, Juan T.; Wu, Jishan; Casado, Juan

    2014-02-01

    A analysis of the electronic and molecular structures of new molecular materials based on zethrene is presented with particular attention to those systems having a central benzo-quinoidal core able to generate Kekulé biradicals whose stability is provided by the aromaticity recovery in this central unit. These Kekulé biradicals display singlet ground electronic states thanks to double spin polarization and have low-energy lying triplet excited states also featured by the aromaticity gain. Pro-aromatization is also the driving force for the stabilization of the ionized species. Moreover, the low energy lying singlet excited states also display a profound biradical fingerprint allowing to singlet exciton fission. These properties are discussed in the context of the size of the zethrene core and of its substitution. The work encompasses all known long zethrenes and makes use of a variety of experimental techniques, such as Raman, UV-Vis-NIR absorption, transient absorption, in situ spectroelectrochemistry and quantum chemical calculations. This study reveals how the insertion of suitable molecular modules (i.e., quinoidal) opens the door to new intriguing molecular properties exploitable in organic electronics.

  4. First principles electronic structure investigation of order of singlet and triplet states of oxyhemoglobin and analysis of possible influence of muon trapping

    International Nuclear Information System (INIS)

    Badu, S. R.; Pink, R. H.; Scheicher, R. H.; Dubey, Archana; Sahoo, N.; Nagamine, K.; Das, T. P.

    2010-01-01

    Interest in the possibility of magnetic character for oxyhemoglobin (OxyHb) has been recently stimulated by the observations of muon spin-lattice relaxation effects studied (Nagamine et al., Proc Jpn Acad Ser B Phys Biol Sci 83:120–126, 2007) with the muon-spin rotation (μSR) technique. In view of this, we have carried out first-principles electronic structure investigations involving Hartree–Fock theory combined with many body perturbation effects for the singlet and triplet states of OxyHb. Our results indicate that using two recent x-ray structural data (Paoli et al., J Mol Biol 256:775, 1996; Park et al., J Mol Biol 360:690, 2006) for OxyHb, for only Hartree–Fock theory without many-body effects included, the singlet state lies above the triplet state by energies of about 0.08 and 0.13 a.u. for the two structures in Paoli et al. (J Mol Biol 256:775, 1996) and Park et al. (J Mol Biol 360:690, 2006). Incorporation of many-body effects by the perturbation method reverses the order, with the triplet state located 0.18 and 0.14 a.u. above the singlet state for the structures in Paoli et al. (J Mol Biol 256:775, 1996) and Park et al. (J Mol Biol 360:690, 2006). Physical reasons for these relative orderings of the singlet and triplet states will be discussed. It is clear that OxyHb by itself would be in a singlet state at room temperature or below, since from our calculation, the triplet state lies about KT above the singlet state with T having the value of 44,098 K and 56,449 K for the two structural data in Paoli et al. (J Mol Biol 256:775, 1996) and Park et al. (J Mol Biol 360:690, 2006). As regards the muon spin-lattice relaxation effects obtained by recent μSR measurements (by Nagamine et al., Proc Jpn Acad Ser B Phys Biol Sci 83:120–126, 2007) at room temperature, the sensitive dependence of the singlet-triplet separation on many-body effects in our investigation suggests that it is possible that the singlet-triplet separation could be reversed or

  5. Indolo[2,3-b]carbazoles with tunable ground states: How Clar's aromatic sextet determines the singlet biradical character

    KAUST Repository

    Luo, Ding

    2014-01-01

    Polycyclic hydrocarbons (PHs) with a singlet biradical ground state have recently attracted extensive interest in physical organic chemistry and materials science. Replacing the carbon radical center in the open-shell PHs with a more electronegative nitrogen atom is expected to result in the more stable aminyl radical. In this work, two kinetically blocked stable/persistent derivatives (1 and 2) of indolo[2,3-b]carbazole, an isoelectronic structure of the known indeno[2,1-b]fluorene, were synthesized and showed different ground states. Based on variable-temperature NMR/ESR measurements and density functional theory calculations, it was found that the indolo[2,3-b]carbazole derivative 1 is a persistent singlet biradical in the ground state with a moderate biradical character (y0 = 0.269) and a small singlet-triplet energy gap (ΔES-T ≅ -1.78 kcal mol-1), while the more extended dibenzo-indolo[2,3-b]carbazole 2 exhibits a quinoidal closed-shell ground state. The difference can be explained by considering the number of aromatic sextet rings gained from the closed-shell to the open-shell biradical resonance form, that is to say, two for compound 1 and one for compound 2, which determines their different biradical characters. The optical and electronic properties of 2 and the corresponding aromatic precursors were investigated by one-photon absorption, transient absorption and two-photon absorption (TPA) spectroscopies and electrochemistry. Amphoteric redox behaviour, a short excited lifetime and a moderate TPA cross section were observed for 2, which can be correlated to its antiaromaticity and small biradical character. Compound 2 showed high reactivity to protic solvents due to its extremely low-lying LUMO energy level. Unusual oxidative dimerization was also observed for the unblocked dihydro-indolo[2,3-b]carbazole precursors 6 and 11. Our studies shed light on the rational design of persistent aminyl biradicals with tunable properties in the future. This journal

  6. Saddle-splay screening and chiral symmetry breaking in toroidal nematics

    OpenAIRE

    Koning, Vinzenz; van Zuiden, Benjamin C.; Kamien, Randall D.; Vitelli, Vincenzo

    2013-01-01

    We present a theoretical study of director fields in toroidal geometries with degenerate planar boundary conditions. We find spontaneous chirality: despite the achiral nature of nematics the director configuration show a handedness if the toroid is thick enough. In the chiral state the director field displays a double twist, whereas in the achiral state there is only bend deformation. The critical thickness increases as the difference between the twist and saddle-splay moduli grows. A positiv...

  7. Numerical analysis on transitions and symmetry-breaking in the wake of a flapping foil

    Science.gov (United States)

    He, Guo-Yi; Wang, Qi; Zhang, Xing; Zhang, Shu-Guang

    2012-12-01

    Flying and marine animals often use flapping wings or tails to generate thrust. In this paper, we will use the simplest flapping model with a sinusoidal pitching motion over a range of frequency and amplitude to investigate the mechanism of thrust generation. Previous work focuses on the Karman vortex street and the reversed Karman vortex street but the transition between two states remains unknown. The present numerical simulation provides a complete scenario of flow patterns from the Karman vortex street to reversed Karman vortex street via aligned vortices and the ultimate state is the deflected Karman vortex street, as the parameters of flapping motions change. The results are in agreement with the previous experiment. We make further discussion on the relationship of the observed states with drag and thrust coefficients and explore the mechanism of enhanced thrust generation using flapping motions.

  8. Symmetry breaking in two interacting populations of quadratic integrate-and-fire neurons

    Science.gov (United States)

    Ratas, Irmantas; Pyragas, Kestutis

    2017-10-01

    We analyze the dynamics of two coupled identical populations of quadratic integrate-and-fire neurons, which represent the canonical model for class I neurons near the spiking threshold. The populations are heterogeneous; they include both inherently spiking and excitable neurons. The coupling within and between the populations is global via synapses that take into account the finite width of synaptic pulses. Using a recently developed reduction method based on the Lorentzian ansatz, we derive a closed system of equations for the neuron's firing rates and the mean membrane potentials in both populations. The reduced equations are exact in the infinite-size limit. The bifurcation analysis of the equations reveals a rich variety of nonsymmetric patterns, including a splay state, antiphase periodic oscillations, chimera-like states, and chaotic oscillations as well as bistabilities between various states. The validity of the reduced equations is confirmed by direct numerical simulations of the finite-size networks.

  9. Symmetry breaking in two interacting populations of quadratic integrate-and-fire neurons.

    Science.gov (United States)

    Ratas, Irmantas; Pyragas, Kestutis

    2017-10-01

    We analyze the dynamics of two coupled identical populations of quadratic integrate-and-fire neurons, which represent the canonical model for class I neurons near the spiking threshold. The populations are heterogeneous; they include both inherently spiking and excitable neurons. The coupling within and between the populations is global via synapses that take into account the finite width of synaptic pulses. Using a recently developed reduction method based on the Lorentzian ansatz, we derive a closed system of equations for the neuron's firing rates and the mean membrane potentials in both populations. The reduced equations are exact in the infinite-size limit. The bifurcation analysis of the equations reveals a rich variety of nonsymmetric patterns, including a splay state, antiphase periodic oscillations, chimera-like states, and chaotic oscillations as well as bistabilities between various states. The validity of the reduced equations is confirmed by direct numerical simulations of the finite-size networks.

  10. Symmetry-Breaking Assisted Landau-Zener Transitions in Rydberg Atoms

    Science.gov (United States)

    Zhang, S. S.; Gao, W.; Cheng, H.; You, L.; Liu, H. P.

    2018-02-01

    We report the observation of a controlled Landau-Zener transition (LZT) in Rydberg atoms by breaking the symmetry of the underlying Hamiltonian. For a nonhydrogenic Rydberg atom inside a changing electric (F ) field, a LZT occurs between the avoided crossing energy levels of neighboring Rydberg states only for a sufficiently high changing rate. If a transverse magnetic (B ) field is applied as we implement, the atomic level symmetry is broken, which causes the Stark manifolds denoted by a different |m | (m is the magnetic quantum number) to interact with each other. The mixed state levels end up pushing the adiabatically repelled target states closer and additionally they serve as stepping stones for the sequential LZTs between the neighboring sublevels. Such a feature significantly decreases the changing rate required for an efficient LZT inside a pure electric field. We report experimental observations that support the above scenario. It opens a versatile approach for engineering a controlled LZT in more general systems.

  11. Rotational symmetry breaking in the topological superconductor SrxBi2Se3 probed by upper-critical field experiments.

    Science.gov (United States)

    Pan, Y; Nikitin, A M; Araizi, G K; Huang, Y K; Matsushita, Y; Naka, T; de Visser, A

    2016-06-28

    Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.

  12. Precision Measurement of Charge Symmetry Breaking in {it}np{it} Elastic Scattering at 347 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Abegg, R.; Berdoz, A.R.; Birchall, J.; Campbell, J.R.; Davis, C.A.; Delheij, P.P.J.; Gan, L.; Green, P.W.; Greeniaus, L.G.; Healey, D.C.; Helmer, R.; Kolb, N.; Korkmaz, E.; Lee, L.; Levy, C.D.P.; Li, J.; Miller, C.A.; Opper, A.K.; Page, S.A.; Postma, H.; Ramsay, W.D.; Soukup, J.; Stinson, G.M.; van Oers, W.T.H.; Zelenski, A.N.; Zhao, J. [TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada)]|[Department of Physics, University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada)]|[Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2N5 (Canada)]|[Laboratory for Technical Physics, Technical University Delft, 2600 GA, Delft (Netherlands)

    1995-08-28

    Charge symmetry breaking in {ital np} elastic scattering at 347 MeV has been measured with high precision. From fits of the measured asymmetry curves over the angular range 53.4{degree}{le}{theta}{sub c.m.}{le}86.9{degree}, the difference in the center-of-mass zero-crossing angles of the analyzing powers was determined to be 0.438{degree}{plus_minus}0.054{degree}(stat){plus_minus}0.051{degree}(syst). Using the experimentally determined slope of the analyzing power, {ital dA}/{ital d}{theta}=({minus}1.35{plus_minus}0.05){times}10{sup {minus}2} deg{sup {minus}1}, this is equivalent to {Delta}{ital A}=[59{plus_minus}7(stat){plus_minus}7(sys){plus_minus}2(syst)]{times}10{sup {minus}4}. Predictions of nucleon-nucleon interaction models based on meson exchange agree well with this result.

  13. Chiral and parity symmetry breaking for planar fermions: Effects of a heat bath and uniform external magnetic field

    International Nuclear Information System (INIS)

    Ayala, Alejandro; Bashir, Adnan; Gutierrez, Enif; Raya, Alfredo; Sanchez, Angel

    2010-01-01

    We study chiral symmetry breaking for relativistic fermions, described by a parity-violating Lagrangian in 2+1-dimensions, in the presence of a heat bath and a uniform external magnetic field. Working within their four-component formalism allows for the inclusion of both parity-even and -odd mass terms. Therefore, we can define two types of fermion antifermion condensates. For a given value of the magnetic field, there exist two different critical temperatures which would render one of these condensates identically zero, while the other would survive. Our analysis is completely general: it requires no particular simplifying hierarchy among the energy scales involved, namely, bare masses, field strength, and temperature. However, we do reproduce some earlier results, obtained or anticipated in literature, corresponding to special kinematical regimes for the parity conserving case. Relating the chiral condensate to the one-loop effective Lagrangian, we also obtain the magnetization and the pair production rate for different fermion species in a uniform electric field through the replacement B→-iE.

  14. Models for mirror symmetry breaking via β-sheet-controlled copolymerization: (i) mass balance and (ii) probabilistic treatment.

    Science.gov (United States)

    Blanco, Celia; Hochberg, David

    2012-12-06

    Experimental mechanisms that yield the growth of homochiral copolymers over their heterochiral counterparts have been advocated by Lahav and co-workers. These chiral amplification mechanisms proceed through racemic β-sheet-controlled polymerization operative in both surface crystallites as well as in solution. We develop two complementary theoretical models for these template-induced desymmetrization processes leading to multicomponent homochiral copolymers. First, assuming reversible β-sheet formation, the equilibrium between the free monomer pool and the polymer strand within the template is assumed. This yields coupled nonlinear mass balance equations whose solutions are used to calculate enantiomeric excesses and average lengths of the homochiral chains formed. The second approach is a probabilistic treatment based on random polymerization. The occlusion probabilities depend on the polymerization activation energies for each monomer species and are proportional to the concentrations of the monomers in solution in the constant pool approximation. The monomer occlusion probabilities are represented geometrically in terms of unit simplexes from which conditions for maximizing or minimizing the likelihood for mirror symmetry breaking can be determined.

  15. Small-angle light scattering symmetry breaking in polymer-dispersed liquid crystal films with inhomogeneous electrically controlled interface anchoring

    Science.gov (United States)

    Loiko, V. A.; Konkolovich, A. V.; Zyryanov, V. Ya.; Miskevich, A. A.

    2017-03-01

    We have described the method of analyzing and reporting on the results of calculation of the small-angle structure of radiation scattered by a polymer-dispersed liquid crystal film with electrically controlled interfacial anchoring. The method is based on the interference approximation of the wave scattering theory and the hard disk model. Scattering from an individual liquid crystal droplet has been described using the anomalous diffraction approximation extended to the case of droplets with uniform and nonuniform interface anchoring at the droplet-polymer boundary. The director field structure in an individual droplet is determined from the solution of the problem of minimizing the volume density of the free energy. The electrooptical effect of symmetry breaking in the angular distribution of scattered radiation has been analyzed. This effect means that the intensities of radiation scattered within angles +θ s and-θ s relative to the direction of illumination in the scattering plane can be different. The effect is of the interference origin and is associated with asymmetry of the phase shift of the wavefront of an incident wave from individual parts of the droplet, which appears due to asymmetry of the director field structure in the droplet, caused by nonuniform anchoring of liquid crystal molecules with the polymer on its surface. This effect is analyzed in the case of normal illumination of the film depending on the interfacial anchoring at the liquid crystal-polymer interface, the orientation of the optical axes of droplets, their concentration, sizes, anisometry, and polydispersity.

  16. Brownian dynamics of self-regulated particles with additional degrees of freedom: Symmetry breaking and homochirality

    Science.gov (United States)

    Bhattacharyya, Debankur; Paul, Shibashis; Ghosh, Shyamolina; Ray, Deb Shankar

    2018-04-01

    We consider the Brownian motion of a collection of particles each with an additional degree of freedom. The degree of freedom of a particle (or, in general, a molecule) can assume distinct values corresponding to certain states or conformations. The time evolution of the additional degree of freedom of a particle is guided by those of its neighbors as well as the temperature of the system. We show that the local averaging over these degrees of freedom results in emergence of a collective order in the dynamics in the form of selection or dominance of one of the isomers leading to a symmetry-broken state. Our statistical model captures the basic features of homochirality, e.g., autocatalysis and chiral inhibition.

  17. Rotational Symmetry Breaking in a Trigonal Superconductor Nb-doped Bi_{2}Se_{3}

    Directory of Open Access Journals (Sweden)

    Tomoya Asaba

    2017-01-01

    Full Text Available The search for unconventional superconductivity has been focused on materials with strong spin-orbit coupling and unique crystal lattices. Doped bismuth selenide (Bi_{2}Se_{3} is a strong candidate, given the topological insulator nature of the parent compound and its triangular lattice. The coupling between the physical properties in the superconducting state and its underlying crystal symmetry is a crucial test for unconventional superconductivity. In this paper, we report direct evidence that the superconducting magnetic response couples strongly to the underlying trigonal crystal symmetry in the recently discovered superconductor with trigonal crystal structure, niobium (Nb-doped Bi_{2}Se_{3}. As a result, the in-plane magnetic torque signal vanishes every 60°. More importantly, the superconducting hysteresis loop amplitude is enhanced along one preferred direction, spontaneously breaking the rotational symmetry. This observation indicates the presence of nematic order in the superconducting ground state of Nb-doped Bi_{2}Se_{3}.

  18. Chains of benzenes with lithium-atom adsorption: Vibrations and spontaneous symmetry breaking

    OpenAIRE

    Ortiz, Yenni P.; Stegmann, Thomas; Klein, Douglas J.; Seligman, Thomas H.

    2016-01-01

    We study effects of different configurations of adsorbates on the vibrational modes as well as symmetries of polyacenes and poly-p-phenylenes focusing on lithium atom adsorption. We found that the spectra of the vibrational modes distinguish the different configurations. For more regular adsorption schemes the lowest states are bending and torsion modes of the skeleton, which are essentially followed by the adsorbate. On poly-p-phenylenes we found that lithium adsorption reduces and often eli...

  19. Symmetry breaking in a localized interacting binary Bose-Einstein condensate in a bichromatic optical lattice

    International Nuclear Information System (INIS)

    Cheng Yongshan; Adhikari, S. K.

    2010-01-01

    By direct numerical simulation of the time-dependent Gross-Pitaevskii equation using the split-step Fourier spectral method, we study different aspects of the localization of a cigar-shaped interacting binary (two-component) Bose-Einstein condensate (BEC) in a one-dimensional bichromatic quasiperiodic optical-lattice potential, as used in a recent experiment on the localization of a BEC [Roati et al., Nature 453, 895 (2008)]. We consider two types of localized states: (i) when both localized components have a maximum of density at the origin x=0, and (ii) when the first component has a maximum of density and the second a minimum of density at x=0. In the noninteracting case, the density profiles are symmetric around x=0. We numerically study the breakdown of this symmetry due to interspecies and intraspecies interactions acting on the two components. Where possible, we have compared the numerical results with a time-dependent variational analysis. We also demonstrate the stability of the localized symmetry-broken BEC states under small perturbation.

  20. Nonlinear buckling behaviour of spherical shells: barriers and symmetry-breaking dimples.

    Science.gov (United States)

    Hutchinson, John W; Thompson, J Michael T

    2017-05-13

    The nonlinear axisymmetric post-buckling behaviour of perfect, thin, elastic spherical shells subject to external pressure and their asymmetric bifurcations are characterized, providing results for a structure/loading combination with an exceptionally nonlinear buckling response. Immediately after the onset of buckling, the buckling mode localizes into a dimple at the poles. The relations among the pressure, the dimple amplitude and the change in volume of the shell are determined over a large range of pole deflections. These results allow accurate evaluation of criteria such as the Maxwell condition for which the energies in the unbuckled and buckled states are the same and evaluation of the influences of pressure versus volume-controlled loadings. Non-axisymmetric bifurcation from the axisymmetric state, which occurs deep into the post-buckling regime in the form of multi-lobed dimples, is also established and discussed.This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.' © 2017 The Author(s).

  1. Finding symmetry breaking Hartree-Fock solutions: The case of triplet instability.

    Science.gov (United States)

    Tóth, Zsuzsanna; Pulay, Peter

    2016-10-28

    Determining the lowest unrestricted Hartree-Fock (UHF) solution is often difficult in even-electron systems. We have developed a deterministic method for locating approximately the UHF minimum using the restricted Hartree-Fock triplet instability matrix. The current method is truncated to fourth order. The minimum energy solution for this model can be determined by solving a small linear system of equations. This solution gives a suitable starting point to determine the exact UHF solution. This should be useful for the black-box determination of active spaces spanned by the fractionally occupied charge natural orbitals of the ground-state UHF wavefunction. The results can be generalized to higher (6th and 8th) degree expansions (odd expansion orders vanish by symmetry), and to other types of instability, including complex instability. The results are illustrated by calculations on ozone, benzene, nitrobenzene, butadiene, hexatriene, octatetraene, dichromium, and nickel porphine. Further examples are given in the supplementary material.

  2. Constraints on the minimal N=1 supergravity theory from electroweak symmetry breaking

    International Nuclear Information System (INIS)

    Giudice, G.F.; Ridolfi, G.

    1988-01-01

    We reanalyze the constraints on the minimal N=1 supergravity extension of the standard model arising from the requirement of a correct spontaneous breakdown of the electroweak symmetry. Driven by recent experimental results, we devote special attention to the case of a top quark much heavier than the conventional choice of 40 GeV, used in previous analyses. Our results are stated in a space of phenomenologically meaningful parameters, providing a direct comparison between the constraints from SU(2) x U(1) breaking and the predictions for supersymmetric particle production. Moreover, an upper bound for the ratio of the two Higgs vacuum expectation values is given, for any value of the top quark mass. (orig.)

  3. Symmetry breaking in fluid dynamics: Lie group reducible motions for real fluids

    International Nuclear Information System (INIS)

    Holm, D.D.

    1976-07-01

    The physics of fluids is based on certain kinematical invariance principles, which refer to coordinate systems, dimensions, and Galilean reference frames. Other, thermodynamic, symmetry principles are introduced by the material description. In the present work, the interplay between these two kinds of invariance principles is used to solve for classes of one-dimensional non-steady isentropic motions of a fluid whose equation of state is of Mie-Gruneisen type. Also, the change in profile and attenuation of weak shock waves in a dissipative medium is studied at the level of Burgers' approximation from the viewpoint of its underlying symmetry structure. The mathematical method of approach is based on the theory of infinitesimal Lie groups. Fluid motions are characterized according to inequivalent subgroups of the full invariance group of the flow description and exact group reducible solutions are presented

  4. Dynamical effects of exchange symmetry breaking in mixtures of interacting bosons

    DEFF Research Database (Denmark)

    Tichy, Malte C.; Sherson, Jacob; Mølmer, Klaus

    2012-01-01

    of two distinguishable species with identical physical properties, that is, which are governed by an isospecific interaction and external potential. In the mean-field limit, the spatial population imbalance of the mixture can be described by the dynamics of a single species in an effective potential...... approximates the full counting statistics well also outside the realm of spin-coherent states. The method is extended to general Bose-Hubbard systems and to their classical mean-field limits, which suggests an effective single-species description of multicomponent Bose gases with weakly an...... with modified properties or, equivalently, with an effective total particle number. The oscillation behavior can be tuned by populating the second species while maintaining the spatial population imbalance and all other parameters constant. In the corresponding many-body approach, the single-species description...

  5. Symmetry breaking in fluid dynamics: Lie group reducible motions for real fluids

    Energy Technology Data Exchange (ETDEWEB)

    Holm, D.D.

    1976-07-01

    The physics of fluids is based on certain kinematical invariance principles, which refer to coordinate systems, dimensions, and Galilean reference frames. Other, thermodynamic, symmetry principles are introduced by the material description. In the present work, the interplay between these two kinds of invariance principles is used to solve for classes of one-dimensional non-steady isentropic motions of a fluid whose equation of state is of Mie-Gruneisen type. Also, the change in profile and attenuation of weak shock waves in a dissipative medium is studied at the level of Burgers' approximation from the viewpoint of its underlying symmetry structure. The mathematical method of approach is based on the theory of infinitesimal Lie groups. Fluid motions are characterized according to inequivalent subgroups of the full invariance group of the flow description and exact group reducible solutions are presented.

  6. Symmetry-Breaking in a Rate Model for a Biped Locomotion Central Pattern Generator

    Directory of Open Access Journals (Sweden)

    Ian Stewart

    2014-01-01

    Full Text Available The timing patterns of animal gaits are produced by a network of spinal neurons called a Central Pattern Generator (CPG. Pinto and Golubitsky studied a four-node CPG for biped dynamics in which each leg is associated with one flexor node and one extensor node, with Ζ2 x Ζ2 symmetry. They used symmetric bifurcation theory to predict the existence of four primary gaits and seven secondary gaits. We use methods from symmetric bifurcation theory to investigate local bifurcation, both steady-state and Hopf, for their network architecture in a rate model. Rate models incorporate parameters corresponding to the strengths of connections in the CPG: positive for excitatory connections and negative for inhibitory ones. The three-dimensional space of connection strengths is partitioned into regions that correspond to the first local bifurcation from a fully symmetric equilibrium. The partition is polyhedral, and its symmetry group is that of a tetrahedron. It comprises two concentric tetrahedra, subdivided by various symmetry planes. The tetrahedral symmetry arises from the structure of the eigenvalues of the connection matrix, which is involved in, but not equal to, the Jacobian of the rate model at bifurcation points. Some of the results apply to rate equations on more general networks.

  7. Probing symmetry and symmetry breaking in resonant soft-x-ray fluorescence spectra of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Glans, P.; Gunnelin, K.; Guo, J. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    Conventional non-resonant soft X-ray emission brings about information about electronic structure through its symmetry and polarization selectivity, the character of which is governed by simple dipole rules. For centro-symmetric molecules with the emitting atom at the inversion center these rules lead to selective emission through the required parity change. For the more common classes of molecules which have lower symmetry or for systems with degenerate core orbitals (delocalized over identical sites), it is merely the local symmetry selectivity that provides a probe of the local atomic orbital contribution to the molecular orbital. For instance, in X-ray spectra of first row species the intensities essentially map the p-density at each particular atomic site, and, in a molecular orbital picture, the contribution of the local p-type atomic orbitals in the LCAO description of the molecular orbitals. The situation is different for resonant X-ray fluorescence spectra. Here strict parity and symmetry selectivity gives rise to a strong frequency dependence for all molecules with an element of symmetry. In addition to symmetry selectivity the strong frequency dependence of resonant X-ray emission is caused by the interplay between the shape of a narrow X-ray excitation energy function and the lifetime and vibrational broadenings of the resonantly excited core states. This interplay leads to various observable effects, such as linear dispersion, resonance narrowing and emission line (Stokes) doubling. Also from the point of view of polarization selectivity, the resonantly excited X-ray spectra are much more informative than the corresponding non-resonant spectra. Examples are presented for nitrogen, oxygen, and carbon dioxide molecules.

  8. Symmetry breaking in frustrated XY models: Results from new self-consistent fluctuation approach and simulations

    Science.gov (United States)

    Behzadi, Azad Esmailov

    1999-10-01

    The critical behavior of the fully frustrated XY model has remained controversial in spite of almost two decades of related research. In this study, we have developed a new method inspired by Netz and Berker's hard-spin mean- field theory. Our approach for XY models yields results consistent with Monte Carlo simulations as the ratio of antiferromagnetic to ferromagnetic interactions is varied. The method captures two phase transitions clearly separated in temperature for ratios of 0.5, 0.6, and 1.5, with these transitions moving closer together in temperature as the interaction ratio approaches 1.0, the fully frustrated case. From the system's chirality as a function of temperature in the critical region, we calculate the critical exponent β in agreement with an Ising transition for all of the interaction ratios studied, including 1.0. This result provides support for the view that there are two transitions, rather than one transition in a new universality class, occurring in the fully frustrated XY model. Finite size effects in this model can be essentially eliminated by rescaling the local magnetization, the quantity retained self- consistently in our computations. This rescaling scheme also shows excellent results when tested on the two- dimensional Ising model, and the method, as generalized, provides a framework for an analytical approach to complex systems. Monte Carlo simulations of the fully frustrated XY model in a magnetic field provide further evidence of two transitions. The magnetic field breaks the rotational symmetry of the model, but the two-fold chiral degeneracy of the ground state persists in the field. This lower degeneracy with the field present makes Monte Carlo simulations converge more rapidly. The critical exponent δ determined from the sublattice magnetizations as a function of field agrees with the value expected for a Kosterlitz-Thouless transition. Further, the zero-field specific heat obtained by extrapolation from simulations in a

  9. Hecate/Grip2a acts to reorganize the cytoskeleton in the symmetry-breaking event of embryonic axis induction.

    Science.gov (United States)

    Ge, Xiaoyan; Grotjahn, Danielle; Welch, Elaine; Lyman-Gingerich, Jamie; Holguin, Christiana; Dimitrova, Eva; Abrams, Elliot W; Gupta, Tripti; Marlow, Florence L; Yabe, Taijiro; Adler, Anna; Mullins, Mary C; Pelegri, Francisco

    2014-06-01

    Maternal homozygosity for three independent mutant hecate alleles results in embryos with reduced expression of dorsal organizer genes and defects in the formation of dorsoanterior structures. A positional cloning approach identified all hecate mutations as stop codons affecting the same gene, revealing that hecate encodes the Glutamate receptor interacting protein 2a (Grip2a), a protein containing multiple PDZ domains known to interact with membrane-associated factors including components of the Wnt signaling pathway. We find that grip2a mRNA is localized to the vegetal pole of the oocyte and early embryo, and that during egg activation this mRNA shifts to an off-center vegetal position corresponding to the previously proposed teleost cortical rotation. hecate mutants show defects in the alignment and bundling of microtubules at the vegetal cortex, which result in defects in the asymmetric movement of wnt8a mRNA as well as anchoring of the kinesin-associated cargo adaptor Syntabulin. We also find that, although short-range shifts in vegetal signals are affected in hecate mutant embryos, these mutants exhibit normal long-range, animally directed translocation of cortically injected dorsal beads that occurs in lateral regions of the yolk cortex. Furthermore, we show that such animally-directed movement along the lateral cortex is not restricted to a single arc corresponding to the prospective dorsal region, but occur in multiple meridional arcs even in opposite regions of the embryo. Together, our results reveal a role for Grip2a function in the reorganization and bundling of microtubules at the vegetal cortex to mediate a symmetry-breaking short-range shift corresponding to the teleost cortical rotation. The slight asymmetry achieved by this directed process is subsequently amplified by a general cortical animally-directed transport mechanism that is neither dependent on hecate function nor restricted to the prospective dorsal axis.

  10. Symmetry breaking and chaos

    International Nuclear Information System (INIS)

    Bunakov, V.E.; Ivanov, I.B.

    1999-01-01

    Connections between the symmetries of Hamiltonian systems in classical and quantum mechanics, on one hand, and their regularity or chaoticity, on the other hand, are considered. The quantum-chaoticity criterion that was proposed previously and which was borrowed from the theory of compound-nucleus resonances is used to analyze the quantum diamagnetic Kepler problem - that is, the motion of a spinless charged particle in a Coulomb and a uniform magnetic field

  11. Magnetically Bistable Nitrenes: Matrix Isolation of Furoylnitrenes in Both Singlet and Triplet States and Triplet 3-Furylnitrene.

    Science.gov (United States)

    Feng, Ruijuan; Lu, Yan; Deng, Guohai; Xu, Jian; Wu, Zhuang; Li, Hongmin; Liu, Qian; Kadowaki, Norito; Abe, Manabu; Zeng, Xiaoqing

    2018-01-10

    Two simple acylnitrenes, 2-furoylnitrene (2) and 3-furoylnitrene (6), were generated through 266 nm laser photolysis of the corresponding azides. Both are magnetically bistable in cryogenic matrices, as evidenced by the direct observation of the closed-shell singlet state with IR spectroscopy in solid Ne, Ar, Kr, Xe, and N 2 matrices (3-40 K) and the triplet state in toluene (10 K) with EPR spectroscopy ( 3 2: |D/hc| = 1.48 cm -1 and |E/hc| = 0.029 cm -1 ; 3 6: |D/hc| = 1.39 cm -1 and |E/hc|c = 0.039 cm -1 ). Subsequent visible-light and UV laser irradiations led to the formation of furyl isocyanates (3 and 7) and ring-opening product 3-cyanoacrolein (9-E and 9-Z), respectively, in which the elusive 3-furylnitrene ( 3 8) was also identified by IR and EPR spectroscopy (|D/hc| = 1.12 cm -1 and |E/hc| = 0.005 cm -1 ).

  12. Rearrangement of van der Waals stacking and formation of a singlet state at T = 90 K in a cluster magnet

    Energy Technology Data Exchange (ETDEWEB)

    Sheckelton, John P.; Plumb, Kemp W.; Trump, Benjamin A.; Broholm, Collin L.; McQueen, Tyrel M.

    2017-01-01

    Insulating Nb3Cl8 is a layered chloride consisting of two-dimensional triangular layers of Seff = 1/2 Nb3Cl13 clusters at room temperature. Magnetic susceptibility measurement show a sharp, hysteretic drop to a temperature independent value below T = 90 K. Specific heat measurements show that the transition is first order, with ΔS ≈ 5 J K-1 mol-1 f.u.-1, and a low temperature T-linear contribution originating from defect spins. Neutron and X-ray diffraction show a lowering of symmetry from trigonal P[3 with combining macron]m1 to monoclinic C2/m symmetry, with a change in layer stacking from –AB–AB– to –AB'–BC'–CA'– and no observed magnetic order. This lowering of symmetry and rearrangement of successive layers evades geometric magnetic frustration to form a singlet ground state. It is the lowest temperature at which a change in stacking sequence is known to occur in a van der Waals solid, occurs in the absence of orbital degeneracies, and suggests that designer 2-D heterostructures may be able to undergo similar phase transitions.

  13. Singlet-paired coupled cluster theory for open shells

    International Nuclear Information System (INIS)

    Gomez, John A.; Henderson, Thomas M.; Scuseria, Gustavo E.

    2016-01-01

    Restricted single-reference coupled cluster theory truncated to single and double excitations accurately describes weakly correlated systems, but often breaks down in the presence of static or strong correlation. Good coupled cluster energies in the presence of degeneracies can be obtained by using a symmetry-broken reference, such as unrestricted Hartree-Fock, but at the cost of good quantum numbers. A large body of work has shown that modifying the coupled cluster ansatz allows for the treatment of strong correlation within a single-reference, symmetry-adapted framework. The recently introduced singlet-paired coupled cluster doubles (CCD0) method is one such model, which recovers correct behavior for strong correlation without requiring symmetry breaking in the reference. Here, we extend singlet-paired coupled cluster for application to open shells via restricted open-shell singlet-paired coupled cluster singles and doubles (ROCCSD0). The ROCCSD0 approach retains the benefits of standard coupled cluster theory and recovers correct behavior for strongly correlated, open-shell systems using a spin-preserving ROHF reference.

  14. Fate of the open-shell singlet ground state in the experimentally accessible acenes: A quantum Monte Carlo study

    Science.gov (United States)

    Dupuy, Nicolas; Casula, Michele

    2018-04-01

    By means of the Jastrow correlated antisymmetrized geminal power (JAGP) wave function and quantum Monte Carlo (QMC) methods, we study the ground state properties of the oligoacene series, up to the nonacene. The JAGP is the accurate variational realization of the resonating-valence-bond (RVB) ansatz proposed by Pauling and Wheland to describe aromatic compounds. We show that the long-ranged RVB correlations built in the acenes' ground state are detrimental for the occurrence of open-shell diradical or polyradical instabilities, previously found by lower-level theories. We substantiate our outcome by a direct comparison with another wave function, tailored to be an open-shell singlet (OSS) for long-enough acenes. By comparing on the same footing the RVB and OSS wave functions, both optimized at a variational QMC level and further projected by the lattice regularized diffusion Monte Carlo method, we prove that the RVB wave function has always a lower variational energy and better nodes than the OSS, for all molecular species considered in this work. The entangled multi-reference RVB state acts against the electron edge localization implied by the OSS wave function and weakens the diradical tendency for higher oligoacenes. These properties are reflected by several descriptors, including wave function parameters, bond length alternation, aromatic indices, and spin-spin correlation functions. In this context, we propose a new aromatic index estimator suitable for geminal wave functions. For the largest acenes taken into account, the long-range decay of the charge-charge correlation functions is compatible with a quasi-metallic behavior.

  15. Variational state based on the Bethe-ansatz solution and a correlated singlet liquid state in the one-dimensional t-J model

    International Nuclear Information System (INIS)

    Kobayashi, K.; Ohe, C.; Iguchi, K.

    1996-01-01

    The one-dimensional t-J model is investigated by the variational Monte Carlo method. A variational wave function based on the Bethe-ansatz solution is proposed, where the spin-charge separation is realized and a long-range correlation factor of Jastrow-type is included. In most regions of the phase diagram, this wave function provides an excellent description of the ground-state properties characterized as a Tomonaga-Luttinger liquid; both the amplitude and exponent of correlation functions are correctly reproduced. For the spin-gap phase, another trial state of correlated singlet pairs with a Jastrow factor is introduced. This wave function shows generalized Luther-Emery-liquid behavior, exhibiting enhanced superconducting correlations and exponential decay of the spin correlation function. Using these two variational wave functions, the whole phase diagram is determined. In addition, relations between the correlation exponent and variational parameters in the trial functions are derived. copyright 1996 The American Physical Society

  16. α decay of the T=1, 2+ state in B10 and isospin symmetry breaking in the A=10 triplet

    Energy Technology Data Exchange (ETDEWEB)

    Kuvin, S. A.; Wuosmaa, A. H.; Lister, C. J.; Avila, M. L.; Hoffman, C. R.; Kay, B. P.; McNeel, D. G.; Morse, C.; McCutchan, E. A.; Santiago-Gonzalez, D.; Winkelbauer, J. R.

    2017-10-01

    The rate of the T = 1, 2(+) to T = 1, 0(+) transition in B-10 (T = 1, T-z = 0) is compared to the analog transitions in Be-10 (T = 1, T-z = -1) and C-10 (T = 1, T-z = +1) to provide constraints on ab initio calculations using realistic nuclear forces. The relevant state in B-10, at E-x = 5.164 MeV, is particle unbound. Therefore, a determination of the B(E2) electromagnetic transition rate requires a precise and accurate determination of the width of the state, as well as the alpha-particle and gamma-ray branching ratios. Previous measurements of the a-particle branching ratio are just barely in agreement. We report on a new study of the alpha-particle branch by studying the B-10(p, p') B-10* reaction in inverse kinematics with the HELIOS spectrometer. The alpha-particle branching ratio that we observe, 0.144 +/- 0.027, is in good agreement with the evaluated value and improves the associated uncertainty. The resulting experimental B(E2) value is 7.0 +/- 2.2 e(2)fm(4) and is more consistent with a flat trend across the A = 10 triplet than previously reported. This is inconsistent with Green's functionMonte Carlo predictions using realistic three-nucleon Hamiltonians, which overpredict the B(E2) value in C-10 and B-10.

  17. Search for time-reversal symmetry breaking order at the (1 1 0) interface of YBa2Cu3O using βNMR

    Science.gov (United States)

    Saadaoui, H.; Morris, G. D.; Chow, K. H.; Hossain, M. D.; Levy, C. D. P.; Parolin, T. J.; Pearson, M. R.; Salman, Z.; Smadella, M.; Song, Q.; Wang, D.; Hentges, P. J.; Greene, L. H.; Kiefl, R. F.; MacFarlane, W. A.

    2009-04-01

    In this paper, we report initial βNMR measurements seeking the spontaneous magnetic fields associated with a time-reversal symmetry breaking (TRSB) order at the (1 1 0) interface of the high temperature superconductor YBa2Cu3O (YBCO). A 2 keV beam of highly spin-polarized Li+8 was implanted into a thin overlayer of silver sputtered onto an oriented YBCO film. The NMR of Li8 in the Ag layer showed additional broadening with an onset below the superconducting transition temperature Tc. This is evidence of spontaneous disordered magnetism which could be associated with TRSB order.

  18. Singlet and triplet state transitions of carotenoids in the antenna complexes of higher-plant photosystem I

    NARCIS (Netherlands)

    Croce, Roberta; Mozzo, Milena; Morosinotto, Tomas; Romeo, Alessandro; Hienerwadel, Rainer; Bassi, Roberta

    2007-01-01

    In this work, the spectroscopic characteristics of carotenoids associated with the antenna complexes of Photosystem I have been studied. Pigment composition, absorption spectra, and laser-induced triplet-minus-singlet (T-S) spectra were determined for native LHCI from the wild type (WT) and lut2

  19. Flavour blindness and patterns of flavour symmetry breaking in lattice simulations of up, down and strange quarks

    Energy Technology Data Exchange (ETDEWEB)

    Bietenholz, W. [Univ. Autonoma de Mexico, Mexico City (Mexico). Inst. de Ciencias Nucleares; Bornyakov, V. [Inst. for High Energy Physics, Protovino (Russian Federation); Inst. for Theoretical and Experimental Physics, Moscow (Russian Federation); Goeckeler, M. [Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)

    2011-02-15

    QCD lattice simulations with 2+1 flavours typically start at rather large up-down and strange quark masses and extrapolate first the strange quark mass to its physical value and then the up-down quark mass. An alternative method of tuning the quark masses is discussed here in which the singlet quark mass is kept fixed, which ensures that the kaon always has mass less than the physical kaon mass. Using group theory the possible quark mass polynomials for a Taylor expansion about the flavour symmetric line are found, first for the general 1+1+1 flavour case and then for the 2+1 flavour case (when two quark flavours are mass degenerate). These enable highly constrained fits to be used in the extrapolation of hadrons to the physical pion mass. Numerical results for the 2+1 flavour case confirm the usefulness of this expansion and an extrapolation to the physical pion mass gives hadron mass values to within a few percent of their experimental values. Singlet quantities remain constant which allows the lattice spacing to be determined from hadron masses (without necessarily being at the physical point). Furthermore an extension of this programme to include partially quenched results is also given. (orig.)

  20. Gravitational waves from the first order electroweak phase transition in the Z3 symmetric singlet scalar model

    Science.gov (United States)

    Matsui, Toshinori

    2018-01-01

    Among various scenarios of baryon asymmetry of the Universe, electroweak baryogenesis is directly connected with physics of the Higgs sector. We discuss spectra of gravitational waves which are originated by the strongly first order phase transition at the electroweak symmetry breaking, which is required for a successful scenario of electroweak baryogenesis. In the Z3 symmetric singlet scalar model, the significant gravitational waves are caused by the multi-step phase transition. We show that the model can be tested by measuring the characteristic spectra of the gravitational waves at future interferometers such as LISA and DECIGO.

  1. Investigation of the charge symmetry breaking reaction dd → {sup 4}Heπ{sup 0} with the WASA-at-COSY facility

    Energy Technology Data Exchange (ETDEWEB)

    Zurek, Maria Katarzyna

    2017-07-01

    Probing elementary symmetries and symmetry breaking tests our understanding of the theory of strong forces, Quantum Chromodynamics. The presented study concentrates on the charge symmetry forbidden reaction dd → {sup 4}Heπ{sup 0}. The aim is to provide experimental results for comparison with predictions from Chiral Perturbation Theory (χ{sub PT}) to study effects induced by quark masses on the hadronic level, e.g., the proton-neutron mass difference. First calculations showed that in addition to the existing high-precision data from TRIUMF and IUCF, more data are required for a precise determination of the parameters of χ{sub PT}. These new data should comprise the measurement of the charge symmetry forbidden dd → {sup 4}Heπ{sup 0} reaction at sufficiently high energy, where the p-wave contribution becomes important. A first measurement with the WASA-at-COSY experiment at an excess energy of ε = 60 MeV was performed, but the results did not allow for a decisive interpretation because of limited statistics. This thesis reports on a second measurement of the dd → {sup 4}Heπ{sup 0} reaction at ε = 60 MeV using an improved WASA detector setup aiming at higher statistics. A sample of 336 ± 43 event candidates have been extracted using a data set from an eight-week long beamtime, and total and differential cross sections have been determined. The angular distribution has been described with a function of the form dσ/dΩ = a + b cos{sup 2}θ*, where θ* is the scattering angle of the pion in the c.m. coordinate system. The obtained parameters a and b and the total cross section are: a = (1.75 ± 0.46(stat.){sup +0.31}{sub -0.8}(syst.)) pb/sr, b = (13.6 ± 2.2(stat.){sup +0.9}{sub -2.7}(syst.)) pb/sr, σ{sub tot} = (79.1 ± 7.3(stat.){sup +1.2}{sub -10.5}(syst.) ± 8.1(norm.) ± 2.0(lumi. syst.)) pb. For this experiment a modified detector setup optimized for a time-of-flight measurement of the forward going particles has been used. After detector

  2. Blinking fluorescence of single donor-acceptor pairs: important role of "dark'' states in resonance energy transfer via singlet levels.

    Science.gov (United States)

    Osad'ko, I S; Shchukina, A L

    2012-06-01

    The influence of triplet levels on Förster resonance energy transfer via singlet levels in donor-acceptor (D-A) pairs is studied. Four types of D-A pair are considered: (i) two-level donor and two-level acceptor, (ii) three-level donor and two-level acceptor, (iii) two-level donor and three-level acceptor, and (iv) three-level donor and three-level acceptor. If singlet-triplet transitions in a three-level acceptor molecule are ineffective, the energy transfer efficiency E=I_{A}/(I_{A}+I_{D}), where I_{D} and I_{A} are the average intensities of donor and acceptor fluorescence, can be described by the simple theoretical equation E(F)=FT_{D}/(1+FT_{D}). Here F is the rate of energy transfer, and T_{D} is the donor fluorescence lifetime. In accordance with the last equation, 100% of the donor electronic energy can be transferred to an acceptor molecule at FT_{D}≫1. However, if singlet-triplet transitions in a three-level acceptor molecule are effective, the energy transfer efficiency is described by another theoretical equation, E(F)=F[over ¯](F)T_{D}/[1+F[over ¯](F)T_{D}]. Here F[over ¯](F) is a function of F depending on singlet-triplet transitions in both donor and acceptor molecules. Expressions for the functions F[over ¯](F) are derived. In this case the energy transfer efficiency will be far from 100% even at FT_{D}≫1. The character of the intensity fluctuations of donor and acceptor fluorescence indicates which of the two equations for E(F) should be used to find the value of the rate F. Therefore, random time instants of photon emission in both donor and acceptor fluorescence are calculated by the Monte Carlo method for all four types of D-A pair. Theoretical expressions for start-stop correlators (waiting time distributions) in donor and acceptor fluorescence are derived. The probabilities w_{N}^{D}(t) and w_{N}^{A}(t) of finding N photons of donor and acceptor fluorescence in the time interval t are calculated for various values of the energy

  3. Magnetic field effects on the soft mode in a singlet ground-state dimer system: a neutron scattering study of Cs3Cr2Br9

    DEFF Research Database (Denmark)

    Leuenberger, Bruno; Gudel, Hans U.; Feile, Rudolf

    1985-01-01

    Neutron scattering experiments in a magnetic field have been performed on the singlet ground-state dimer system Cs3Cr2Br9. At low fields the Zeeman splitting of the soft mode evolves in agreement with the isotropic random-phase approximation (RPA) model, with the notable absence of a quasielastic...... peak. At a temperature of 1.7K the expected long-range magnetic order is not found at the predicted field of 2.8 T, indicating the shortcomings of the isotropic RPA model in the critical region. Magnetic intensity on the weak nuclear Bragg peak (1¯1¯4) indicates a probable ordering with a ferromagnetic...

  4. Tensor network methods for the simulation of open quantum dynamics in multichromophore systems: Application to singlet fission in novel pentacene dimers

    Science.gov (United States)

    Chin, Alex

    Singlet fission (SF) is an ultrafast process in which a singlet exciton spontaneously converts into a pair of entangled triplet excitons on neighbouring organic molecules. As a mechanism of multiple exciton generation, it has been suggested as a way to increase the efficiency of organic photovoltaic devices, and its underlying photophysics across a wide range of molecules and materials has attracted significant theoretical attention. Recently, a number of studies using ultrafast nonlinear optics have underscored the importance of intramolecular vibrational dynamics in efficient SF systems, prompting a need for methods capable of simulating open quantum dynamics in the presence of highly structured and strongly coupled environments. Here, a combination of ab initio electronic structure techniques and a new tensor-network methodology for simulating open vibronic dynamics is presented and applied to a recently synthesised dimer of pentacene (DP-Mes). We show that ultrafast (300 fs) SF in this system is driven entirely by symmetry breaking vibrations, and our many-body approach enables the real-time identification and tracking of the ''functional' vibrational dynamics and the role of the ''bath''-like parts of the environment. Deeper analysis of the emerging wave functions points to interesting links between the time at which parts of the environment become relevant to the SF process and the optimal topology of the tensor networks, highlighting the additional insight provided by moving the problem into the natural language of correlated quantum states and how this could lead to simulations of much larger multichromophore systems Supported by The Winton Programme for the Physics of Sustainability.

  5. Minimal flavour violation in the quark and lepton sector and the impact of extra dimensions on flavour changing neutral currents and electroweak symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Weiler, A.

    2007-01-16

    We study flavor-changing decays of hadrons and leptons and an extra-dimensional approach to electroweak symmetry breaking. Specifically we study the framework of Minimal Flavour Violation (MFV) as an explanation of the flavour problem. We discuss the impact of a specific extra-dimensional model of the MFV class on flavour changing neutral currents. We derive model-independent upper bounds on rare decays. -We discuss the extension of the MFV framework from the quark to the lepton sector and show how baryogenesis through leptogenesis can be achieved and examine if possible correlations with charged lepton flavour violation exist. We discuss the dynamical breaking of the electroweak symmetry in extra dimensions by unifying gauge and Higgs fields and we show that realistic models are possible once the extra dimension is strongly curved. (orig.)

  6. Minimal flavour violation in the quark and lepton sector and the impact of extra dimensions on flavour changing neutral currents and electroweak symmetry breaking

    International Nuclear Information System (INIS)

    Weiler, A.

    2007-01-01

    We study flavor-changing decays of hadrons and leptons and an extra-dimensional approach to electroweak symmetry breaking. Specifically we study the framework of Minimal Flavour Violation (MFV) as an explanation of the flavour problem. We discuss the impact of a specific extra-dimensional model of the MFV class on flavour changing neutral currents. We derive model-independent upper bounds on rare decays. -We discuss the extension of the MFV framework from the quark to the lepton sector and show how baryogenesis through leptogenesis can be achieved and examine if possible correlations with charged lepton flavour violation exist. We discuss the dynamical breaking of the electroweak symmetry in extra dimensions by unifying gauge and Higgs fields and we show that realistic models are possible once the extra dimension is strongly curved. (orig.)

  7. The ferromagnetic-spin glass transition in PdMn alloys: symmetry breaking of ferromagnetism and spin glass studied by a multicanonical method.

    Science.gov (United States)

    Kato, Tomohiko; Saita, Takahiro

    2011-03-16

    The magnetism of Pd(1-x)Mn(x) is investigated theoretically. A localized spin model for Mn spins that interact with short-range antiferromagnetic interactions and long-range ferromagnetic interactions via itinerant d electrons is set up, with no adjustable parameters. A multicanonical Monte Carlo simulation, combined with a procedure of symmetry breaking, is employed to discriminate between the ferromagnetic and spin glass orders. The transition temperature and the low-temperature phase are determined from the temperature variation of the specific heat and the probability distributions of the ferromagnetic order parameter and the spin glass order parameter at different concentrations. The calculation results reveal that only the ferromagnetic phase exists at x glass phase exists at x > 0.04, and that the two phases coexist at intermediate concentrations. This result agrees semi-quantitatively with experimental results.

  8. Switching through symmetry breaking for transmission in a T-shaped photonic waveguide coupled with two identical nonlinear micro-cavities.

    Science.gov (United States)

    Bulgakov, Evgeny; Sadreev, Almas

    2011-08-10

    Using coupled mode theory we consider transmission in a T-shaped waveguide coupled with two identical symmetrically positioned nonlinear micro-cavities with mirror symmetry. For input power injected into the central waveguide we show the existence of a symmetry breaking solution which is a result of mixing of the symmetrical input wave with an antisymmetric standing wave in the Fabry-Pérot interferometer. With growth of the input power, a feature in the form of loops arises in the solution which originates from bistability in the transmission in the output left/right waveguide coupled with the first/second nonlinear cavity. The domains of stability of the solution are found. The breaking of mirror symmetry gives rise to nonsymmetrical left and right outputs. We demonstrate that this phenomenon can be explored for all-optical switching of light transmission from the left output waveguide to the right one by application of input pulses.

  9. Stem Cell Differentiation Stage Factors and Their Role in Triggering Symmetry Breaking Processes during Cancer Development: A Quantum Field Theory Model for Reprogramming Cancer Cells to Healthy Phenotypes.

    Science.gov (United States)

    Biava, Pier Mario; Burigana, Fabio; Germano, Roberto; Kurian, Philip; Verzegnassi, Claudio; Vitiello, Giuseppe

    2017-09-20

    A long history of research has pursued the use of embryonic factors isolated during cell differentiation processes for the express purpose of transforming cancer cells back to healthy phenotypes. Recent results have clarified that the substances present at different stages of cell differentiation-which we call stem cell differentiation stage factors (SCDSFs)-are proteins with low molecular weight and nucleic acids that regulate genomic expression. The present review summarizes how these substances, taken at different stages of cellular maturation, are able to retard proliferation of many human tumor cell lines and thereby reprogram cancer cells to healthy phenotypes. The model presented here is a quantum field theory (QFT) model in which SCDSFs are able to trigger symmetry breaking processes during cancer development. These symmetry breaking processes, which lie at the root of many phenomena in elementary particle physics and condensed matter physics, govern the phase transitions of totipotent cells to higher degrees of diversity and order, resulting in cell differentiation. In cancers, which share many genomic and metabolic similarities with embryonic stem cells, stimulated re-differentiation often signifies the phenotypic reversion back to health and non-proliferation. In addition to acting on key components of the cellular cycle, SCDSFs are able to reprogram cancer cells by delicately influencing the cancer microenvironment, modulating the electrochemistry and thus the collective electrodynamic behaviors between dipole networks in biomacromolecules and the interstitial water field. Coherent effects in biological water, which are derived from a dissipative QFT framework, may offer new diagnostic and therapeutic targets at a systemic level, before tumor instantiation occurs in specific tissues or organs. Thus, by including the environment as an essential component of our model, we may push the prevailing paradigm of mutation-driven oncogenesis toward a closer

  10. Generation of Triplet Excited States via Photoinduced Electron Transfer in meso-anthra-BODIPY: Fluorogenic Response toward Singlet Oxygen in Solution and in Vitro

    KAUST Repository

    Filatov, Mikhail A.

    2017-04-14

    Heavy atom-free BODIPY-anthracene dyads (BADs) generate locally excited triplet states by way of photoinduced electron transfer (PeT), followed by recombination of the resulting charge-separated states (CSS). Subsequent quenching of the triplet states by molecular oxygen produces singlet oxygen (1O2), which reacts with the anthracene moiety yielding highly fluorescent species. The steric demand of the alkyl substituents in the BODIPY subunit defines the site of 1O2 addition. Novel bis- and tetraepoxides and bicyclic acetal products, arising from rearrangements of anthracene endoperoxides were isolated and characterized. 1O2 generation by BADs in living cells enables visualization of the dyads distribution, promising new imaging applications.

  11. Singlet oxygen quenching by oxygen in tetraphenyl-porphyrin solutions

    International Nuclear Information System (INIS)

    Dedic, Roman; Korinek, Miloslav; Molnar, Alexander; Svoboda, Antonin; Hala, Jan

    2006-01-01

    Time-resolved measurement of singlet oxygen infrared phosphorescence is a powerful tool for determination of quantum yields and kinetics of its photosensitization. This technique was employed to investigate in detail the previously observed effect of singlet oxygen quenching by oxygen. The question whether the singlet oxygen is quenched by oxygen in ground or in excited state was addressed by study of two complementary dependencies of singlet oxygen lifetimes: on dissolved oxygen concentration and on excitation intensity. Oxygen concentration dependence study of meso-tetra(4-sulphonato)phenylporphyrin (TPPS 4 ) phosphorescence kinetics showed linearity of the dependence of TPPS 4 triplet state rate-constant. Corresponding bimolecular quenching constant of (1.5±0.1)x10 9 l/mol s was obtained. On the other hand, rate constants of singlet oxygen depopulation exhibit nonlinear dependence on oxygen concentration. Comparison of zero oxygen concentration-extrapolated value of singlet oxygen lifetime of (6.5±0.4) μs to (3.7±0.1) μs observed under air-saturated conditions indicates importance of the effect of quenching of singlet oxygen by oxygen. Upward-sloping dependencies of singlet oxygen depopulation rate-constant on excitation intensity evidence that singlet oxygen is predominantly quenched by oxygen in excited singlet state

  12. Stability of singlet and triplet trions in carbon nanotubes

    International Nuclear Information System (INIS)

    Ronnow, Troels F.; Pedersen, Thomas G.; Cornean, Horia D.

    2009-01-01

    We investigate singlet and triplet trion states in semiconducting carbon nanotubes using a one-dimensional model. It is concluded that singlet trion states in bind up to 13.6% stronger than exciton states, and that they lower the optical transition energy with up to 50% of the tight binding band gap energy.

  13. Stability of singlet and triplet trions in carbon nanotubes

    DEFF Research Database (Denmark)

    Rønnow, Troels Frimodt; Pedersen, Thomas Garm; Cornean, Horia

    2009-01-01

    We investigate singlet and triplet trion states in semiconducting carbon nanotubes using a one-dimensional model. It is concluded that singlet trion states in bind up to 13.5% stronger than exciton states, and that they lower the optical transition energy with up to 50% of the tight binding band...

  14. Glow discharge in singlet oxygen

    International Nuclear Information System (INIS)

    Vagin, N.P.; Ionin, A.A.; Klimachev, Yu.M.; Sinitsyn, D.V.; Yuryshev, N.N.; Kochetov, I.V.; Napartovich, A.P.

    2003-01-01

    Currently, there is no experimental data on the plasma balance in gas mixtures with a high content of singlet delta oxygen O 2 ( 1 Δ g ). These data can be obtained by studying the parameters of an electric discharge in singlet oxygen produced by a chemical generator. The O 2 ( 1 Δ g ) molecules significantly change the kinetics of electrons and negative ions in plasma. Hence, the discharge conditions at low and high O 2 ( 1 Δ g ) concentrations are very different. Here, the parameters of the positive column of a glow discharge in a gas flow from a chemical singlet-oxygen generator are studied. It is experimentally shown that, at an O 2 ( 1 Δ g ) concentration of 50% and at pressures of 1.5 and 2 torr, the electric field required to sustain the discharge is considerably lower than in the case when all of the oxygen molecules are in the ground state. A theoretical model of the glow discharge is proposed whose predictions are in good agreement with the experimental data

  15. Time-resolved studies on the photoisomerization of a phenylene-silylene-vinylene type compound in its first singlet excited state

    International Nuclear Information System (INIS)

    Burdzinski, G.; Bayda, M.; Hug, G.L.; Majchrzak, M.; Marciniec, B.; Marciniak, B.

    2011-01-01

    In femtosecond laser-flash photolysis experiments, the first singlet excited state of trans-ST, ((E,E)-{1,4-bis(2-dimethylphenylsilyl)ethenyl}benzene) showed a strong S1(π,π * )-Sn absorption band at 540 nm in acetonitrile and at 550 nm in hexane. The lifetime of this state was determined to be 13.2±2.0 and 11.1±1.5 ps, respectively. Intersystem crossing was shown not to be a principal route for the deactivation of this S1 state of trans-ST. Evidence for this conclusion involved two complementary nanosecond laser-flash photolysis experiments. In one experiment involving direct excitation, no transient absorption spectrum was detected in the 350-650 nm spectral range. Yet, in the second experiment, on triplet sensitization, using xanthone, a transient absorption at 400 nm was tentatively assigned to the triplet state absorption of trans-ST. Photoisomerization was monitored in nanosecond time-resolved bleaching experiments. From these experiments the trans-cis photoisomerization quantum yield was determined to be 0.23 on direct trans-ST excitation. In a xanthone-sensitized stationary-state excitation experiment, the trans-cis isomerization quantum yield was determined to be 0.32. The main deactivation route of trans-ST in its S1 state is repopulation of the ground state directly through internal conversion or with the intermediacy of conformers with twisted geometry.

  16. Intramolecular Singlet Fission in Quinoidal Bi- and Tetrathiophenes: A Comparative Study of Low-Lying Excited Electronic States and Potential Energy Surfaces.

    Science.gov (United States)

    Momeni, Mohammad R

    2016-10-11

    Quinoidal bithiophene has recently been introduced ( Varnavski, O. et al. J. Phys. Chem. Lett. 2015 , 6 , 1375 - 1384 ) as a very promising isolated organic compound for intramolecular singlet fission (iSF) with an outstanding SF quantum yield of ≈180%. In contrast, another recent study ( Ren, L. et al. J. Am. Chem. Soc. 2015 , 137 , 11294 - 11302 ) revealed that quinoidal tetrathiophenes have no activity in the iSF process and are strong fluorophores instead, with measured fluorescent quantum yields up to 53.1%. Using DFT and TD-DFT methods, the authors of the second contribution attributed the marked differences between these compounds to faster reverse T 2 → S 1 intersystem crossing processes in the tetrathiophenes. To address this unprecedented discrepancy, quinoidal bithiophene and tetrathiophene compounds and their derivatives are carefully examined using the CASPT2 technique. Theoretical evidence is provided through detailed investigation of CASPT2 potential energy surfaces of different singlet and triplet states involved in the iSF process. Through comparison of the CASPT2 results with the CASSCF and RAS-2SF data, it is found that the dynamic electron correlation present in the CASPT2 method plays a crucial role for correct description of the multiexciton nature of the triplet pair 1 [TT] state in quinoidal bi- and tetrathiophenes. Effects of substitution and structural modification on iSF activity of these compounds are also examined using the CASPT2 method where the obtained results are in accordance with previous experimental predictions. These results contribute to a better understanding of the iSF mechanism in quinoidal systems which could be relevant for designing new iSF active compounds.

  17. Sensitivity of ATLAS to alternative mechanisms of electroweak symmetry breaking in vector boson scattering qq{yields}qql{nu}l{nu}

    Energy Technology Data Exchange (ETDEWEB)

    Schumacher, Jan W.

    2010-10-15

    An analysis of the expected sensitivity of the ATLAS experiment at the Large Hadron Collider at CERN to alternative mechanisms of electroweak symmetry breaking in the dileptonic vector boson scattering channel is presented. With the generalized K-Matrix model of vector boson scattering recently implemented in the event generator Whizard, several additional resonances are investigated. Whizard is validated for ATLAS use and an interface for the Les Houches event format is adapted for the ATLAS software Athena. Systematic model and statistical Monte Carlo uncertainties are reduced with a signal definition using events reweighted in the couplings g of the new resonances. Angular correlations conserved by Whizard are used in the event selection. A multivariate analyzer is trained to take into account correlations between the selection variables and thereby to improve the sensitivity compared to cut analyses. The statistical analysis is implemented with a profile likelihood method taking into account systematic uncertainties and statistical uncertainties from Monte Carlo. Ensemble tests are performed to assure the applicability of the method. Expected discovery significances and coupling limits for new additional resonances in vector boson scattering are determined. (orig.)

  18. Lorentz-like force emerging from kinematic interactions between electrons and nuclei in molecules: A quantum mechanical origin of symmetry breaking that can trigger molecular chirality

    Science.gov (United States)

    Takatsuka, Kazuo

    2017-02-01

    The Longuet-Higgins (Berry) phase arising from nonadiabatic dynamics and the Aharonov-Bohm phase associated with the dynamics of a charged particle in the electromagnetic vector potential are well known to be individually a manifestation of a class of the so-called geometrical phase. We herein discuss another similarity between the force working on a charged particle moving in a magnetic field, the Lorentz force, and a force working on nuclei while passing across a region where they have a strong quantum mechanical kinematic (nonadiabatic) coupling with electrons in a molecule. This kinematic force is indeed akin to the Lorentz force in that its magnitude is proportional to the velocity of the relevant nuclei and works in the direction perpendicular to its translational motion. Therefore this Lorentz-like nonadiabatic force is realized only in space of more or equal to three dimensions, thereby highlighting a truly multi-dimensional effect of nonadiabatic interaction. We investigate its physical significance qualitatively in the context of breaking of molecular spatial symmetry, which is not seen otherwise without this force. This particular symmetry breaking is demonstrated in application to a coplanar collision between a planar molecule and an atom sharing the same plane. We show that the atom is guided by this force to the direction out from the plane, resulting in a configuration that distinguishes one side of the mirror plane from the other. This can serve as a trigger for the dynamics towards molecular chirality.

  19. Combining symmetry breaking and restoration with configuration interaction: A highly accurate many-body scheme applied to the pairing Hamiltonian

    Science.gov (United States)

    Ripoche, J.; Lacroix, D.; Gambacurta, D.; Ebran, J.-P.; Duguet, T.

    2017-01-01

    Background: Ab initio many-body methods have been developed over the past ten years to address mid-mass nuclei. In their best current level of implementation, their accuracy is of the order of a few percent error on the ground-state correlation energy. Recently implemented variants of these methods are operating a breakthrough in the description of medium-mass open-shell nuclei at a polynomial computational cost while putting state-of-the-art models of internucleon interactions to the test. Purpose: As progress in the design of internucleon interactions is made, and as questions one wishes to answer are refined in connection with increasingly available experimental data, further efforts must be made to tailor many-body methods that can reach an even higher precision for an even larger number of observable quantum states or nuclei. The objective of the present work is to contribute to such a quest by designing and testing a new many-body scheme. Methods: We formulate a truncated configuration-interaction method that consists of diagonalizing the Hamiltonian in a highly truncated subspace of the total N -body Hilbert space. The reduced Hilbert space is generated via the particle-number projected BCS state along with projected seniority-zero two- and four-quasiparticle excitations. Furthermore, the extent by which the underlying BCS state breaks U(1 ) symmetry is optimized in the presence of the projected two- and four-quasiparticle excitations. This constitutes an extension of the so-called restricted variation after projection method in use within the frame of multireference energy density functional calculations. The quality of the newly designed method is tested against exact solutions of the so-called attractive pairing Hamiltonian problem. Results: By construction, the method reproduces exact results for N =2 and N =4 . For N =(8 ,16 ,20 ) , the error in the ground-state correlation energy is less than (0.006%, 0.1%, 0.15%) across the entire range of

  20. The development of efficient two-photon singlet oxygen sensitizers

    DEFF Research Database (Denmark)

    Nielsen, Christian Benedikt

    the singlet oxygen yield and the two-photon absorption cross section, where it was revealed that a careful balancing of the amount of charge transfer present in theexcited state of the sensitizer is necessary to obtain both a high singlet oxygen quantum yield and a high two-photon cross section. An increasing...... amount of charge-transfer is beneficial for high two-photon absorption cross sections but iscounter-productive for singlet oxygen generation. The design principles obtained from the studies in lipophilic solvents were applied to synthesize water-soluble twophoton singlet oxygen sensitizers......The development of efficient two-photon singlet oxygen sensitizers is addressed focusing on organic synthesis. Photophysical measurements were carried out on new lipophilic molecules, where two-photon absorption cross sections and singlet oxygen quantumyields were measured. Design principles...

  1. Symmetries and symmetry breaking beyond the electroweak theory; Symetries et brisures de symetries au-dela de la theorie electrofaible

    Energy Technology Data Exchange (ETDEWEB)

    Grojean, Ch

    1999-05-04

    The Glashow-Salam-Weinberg theory describing electroweak interactions is one of the best successes of quantum field theory; it has passed all the experimental tests of particles physics with a high accuracy. However, this theory suffers from some deficiencies in the sense that some parameters, especially those involved in the generation of the mass of the elementary particles, are fixed to unnatural values. Moreover gravitation whose quantization cannot be achieved in ordinary quantum filed theory is hot taken into account. The aim of this PhD dissertation is to study some theories beyond the Standard Model and inspired by superstring theories. My endeavour has been to develop theoretical aspects of an effective dynamical description of one of the soltonic states of the strongly coupled strings. An important part of my results is also devoted to a more phenomenological analysis of the low energy effects of the symmetries that assure the coherence of the theories at high energy: these symmetries could explain the fermion mass hierarchy and could be directly observable in collider experiments. It is also shown how the geometrical properties of compactified spaces characterize the vacuum of string theory in a non-perturbative regime; such a vacuum can be used to construct a unified theory of gauge and gravitational interactions with a supersymmetry softy broken at a TcV scale. (author)

  2. Numerical investigation of symmetry breaking and critical behavior of the acoustic streaming field in high-intensity discharge lamps

    International Nuclear Information System (INIS)

    Baumann, Bernd; Schwieger, Joerg; Wolff, Marcus; Manders, Freddy; Suijker, Jos

    2015-01-01

    For energy efficiency and material cost reduction it is preferred to drive high-intensity discharge lamps at frequencies of approximately 300 kHz. However, operating lamps at these high frequencies bears the risk of stimulating acoustic resonances inside the arc tube, which can result in low frequency light flicker and even lamp destruction. The acoustic streaming effect has been identified as the link between high frequency resonances and low frequency flicker. A highly coupled three-dimensional multiphysics model has been set up to calculate the acoustic streaming velocity field inside the arc tube of high-intensity discharge lamps. It has been found that the velocity field suffers a phase transition to an asymmetrical state at a critical acoustic streaming force. In certain respects the system behaves similar to a ferromagnet near the Curie point. It is discussed how the model allows to investigate the light flicker phenomenon. Concerning computer resources the procedure is considerably less demanding than a direct approach with a transient model. (paper)

  3. Optical detection of singlet oxygen from single cells

    DEFF Research Database (Denmark)

    Snyder, John; Skovsen, Esben; Lambert, John D. C.

    2006-01-01

    The lowest excited electronic state of molecular oxygen, singlet molecular oxygen, O2(a 1g), is a reactive species involved in many chemical and biological processes. To better understand the roles played by singlet oxygen in biological systems, particularly at the sub-cellular level, optical tools...

  4. Symmetry-Breaking Transitions in RECuAs2-xPx (RE=Sm, Gd, Ho, and Er)

    Energy Technology Data Exchange (ETDEWEB)

    Mozharivskyj, Yurij [Iowa State Univ., Ames, IA (United States)

    2002-01-01

    Structural changes resulting in lower symmetries can be understood in terms of electronic instabilities and Coulomb interactions. The interplay of these two interrelated factors is complicated and difficult to analyze. The RECuAs2-xP x phases, because of the variation in the chemical content (As/P substitution), allow, with the aid of band structures, Madelung energies and Landau theory, a partial unraveling of the forces important in the symmetry-breaking transitions in RECuAs2-xP x (RE = Sm, Gd, Ho and Er). Distortions of the P layers in SmCu1.15P2, GdCuP2.20 and ErCuP2 are usefully thought of as generalized Peierls distortions, i.e., they lower the electronic (and total) energy and lead to more stable structures. On the other hand, the P4/nmm → Pmmn transitions, which are observed in all studied arsenophosphide series and occur upon substitution of P for As, originate from the B1g vibrational mode and are structural adaptations to smaller P atoms. These transitions provide tighter atomic packing and better Coulomb interactions. Configurational contribution to the entropy becomes important in stabilizing the mixed occupancy in the RECuAs 2-xP x arsenophosphides. While geometric and electronic factors favor separation of the As and P atoms over two different crystallographic sites, configurational entropy stabilizes the As/P mixing on these two sites.;Progress in the research on RECuAs2-xP x was dependent upon the ability of Landau theory to predict, explain and dismiss structural models and transitions. The space group Pmmn (arising from the B 1g vibrational mode) in all mixed arsenophosphides and the existence of these mixed arsenophosphides followed from the analysis of GdCuAs 2 and GdCuP2, using Landau theory. The impossibility of obtaining the high-symmetry structure (P4/nmm) and the low symmetry structure

  5. Roles of singlet oxygen and triplet excited state of dissolved organic matter formed by different organic matters in bacteriophage MS2 inactivation

    KAUST Repository

    Rosado-Lausell, Sahid L.

    2013-09-01

    Inactivation of bacteriophage MS2 by reactive oxygen species (ROS) and triplet excited state of dissolved organic matter (3DOM*) produced by irradiation of natural and synthetic sensitizers with simulated sunlight of wavelengths greater than 320nm was investigated. Natural sensitizers included purified DOM isolates obtained from wastewater and river waters, and water samples collected from Singapore River, Stamford Canal, and Marina Bay Reservoir in Singapore. Linear correlations were found between MS2 inactivation rate constants (kobs) and the photo-induced reaction rate constants of 2,4,6-trimethylphenol (TMP), a probe compound shown to react mainly with 3DOM*. Linear correlations between MS2 kobs and singlet oxygen (1O2) concentrations were also found for both purified DOM isolates and natural water samples. These correlations, along with data from quenching experiments and experiments with synthetic sensitizers, Rose Bengal (RB), 3\\'-methoxyacetophenone (3\\'-MAP), and nitrite (NO2-), suggest that 1O2, 3DOM*, and hydroxyl radicals (•OH) could inactivate bacteriophage MS2. Linear correlations between MS2 kobs and Specific Ultraviolet Absorption determined at 254nm (SUVA254) were also found for both purified DOM isolates and natural samples. These results suggest the potential use of TMP as a chemical probe and SUVA254 as an indicator for virus inactivation in natural and purified DOM water samples. © 2013 Elsevier Ltd.

  6. Luminescence property and lowest excited singlet state level of various carotenes; Shuju no karochinrui no hako tokusei to saitei reiki -juko jotai jun'i

    Energy Technology Data Exchange (ETDEWEB)

    Ito, T. [Miyagi Midical Univ., Miyagi (Japan)

    2000-01-01

    Specification of the lowest excited singlet state (S{sub l}) of the butadiene which is the simplest {pi} electron conjugated system molecule has not sufficiently clarified at present. Recently, Andersson et al. found the weak light emission which was considered to be the S{sub 1} fluorescence in a near infrared region in a room temperature solution of {beta}- carotene (n=11), and specified the S{sub 1} level in 14,200{+-}500cm {sup -1}. And, Fujii et al. reported the S{sub 1} fluorescence of spheroidine (n=10). In very recent, Christensen et al. measured the comparatively clear fluorescence spectrum of carotenes n=5 to 11 separated by HPLC in EPA glass at 77K, and systematically examined the unique luminescence property observed in polyene. Christensen et al. issued the warning for the rough conventional method that the S{sub 1} level was estimated from the S{sub 1} fluorescence lifetime of the polyene molecule using the comprehensive energy gap law, because the ratio of quantum yield of the S{sub 1} and S{sub 2} fluorescence is different by the substituent type of the polyene end even if n is same. (NEDO)

  7. S1←S0 vibronic spectra and structure of cyclopropanecarboxaldehyde molecule in the S1 lowest excited singlet electronic state

    International Nuclear Information System (INIS)

    Godunov, I.A.; Yakovlev, N.N.; Terentiev, R.V.; Maslov, D.V.; Bataev, V.A.; Abramenkov, A.V.

    2016-01-01

    The S 1 ←S 0 vibronic spectra of gas-phase absorption at room temperature and fluorescence excitation of jet-cooled cyclopropanecarboxaldehyde (CPCA, c-C 3 H 5 CHO)were obtained and analyzed. In addition, the quantum chemical calculation (CASPT2/cc-pVTZ)was carried out for CPCA in the ground (S 0 ) and lowest excited singlet (S 1 ) electronic states. As a result, it was proved that the S 1 ←S 0 electronic excitation of the CPCA conformers (syn and anti) causes (after geometrical relaxation) significant structural changes, namely, the carbonyl fragments become non-planar and the cyclopropyl groups rotate around the central C–C bond. As a consequence, the potential energy surface of CPCA in the S 1 state has six minima, 1ab, 2ab, and 3ab, corresponding to three pairs of mirror symmetry conformers: a and b. It was shown that vibronic bands of experimental spectra can be assigned to the 2(S 1 )←syn(S 0 ) electronic transition with the origin at 30,481 cm −1 . A number of fundamental vibrational frequencies for the 2 conformer of CPCA were assigned. In addition, several inversional energy levels for the 2 conformer were found and the 2a↔2b potential function of inversion was determined. The experimental barrier to inversion and the equilibrium angle between the CH bond and the CCO plane were calculated as 570 cm −1 and 28°, respectively. - Highlights: • S 1 ←S 0 vibronic gas-phase absorption spectrum of cyclopropanecarboxaldehyde (CPCA). • S 1 ←S 0 fluorescence excitation spectrum of CPCA. • Ab initio calculation for CPCA in S 0 and S 1 electronic states. • Structural changes of the CPCA at S 1 ←S 0 electronic excitation.

  8. Colour singlets in perturbative QCD

    International Nuclear Information System (INIS)

    Bassetto, A.

    1979-01-01

    In the axial gauge and at the leading log level, a definite and consistent picture seems to emerge of a parton decay into states in which many partons are found just before confinement should take place. They are grouped into colourless clusters in a number sufficient to exhaust the ''final'' state, still possessing a finite average mass. This result is peculiar of QCD, in particular of its non-abelian nature. Large transverse momenta or more generally average invariant quantities of partons are mainly due to the multiplicities involved in the branching processes. If eventually confinement would convert these clusters into hadrons (and this is of course the main issue which has still to be proven) without a large rearrangement of the colour lines, the picture we have found for colour singlets could apply to the real hadronic world. (author)

  9. A study of the low-lying singlet and triplet electronic states of chlorophyll A and B

    Directory of Open Access Journals (Sweden)

    Etinski Mihajlo

    2013-01-01

    Full Text Available Chlorophylls have been extensively investigated both experimentally and theoretically owing to the fact that they are essential for photosynthesis. We have studied two forms of chlorophyll, chlorophyll a and chlorophyll b, by means of density functional theory. Optimization of S0, S1 and T1 states was performed with the B3-LYP functional. The computed fluorescence lifetimes show good agreement with the available experimental data. The electronic adiabatic energies of S1 and T1 states are 2.09/2.12 and 1.19/1.29 eV for chlorophyll a and chlorophyll b respectively. We discussed the implications of this results on the triplet formation. Also, the calculated vertical ionization potentials shows good agreement with the experimental results. [Projekat Ministarstva nauke Reoublike Srbije, br. 172040

  10. Quenching Enhancement of the Singlet Excited State of Pheophorbide-a by DNA in the Presence of the Quinone Carboquone

    OpenAIRE

    Díaz-Espinosa, Yisaira; Crespo-Hernández, Carlos E.; Alegría, Antonio E.; García, Carmelo; Arce, Rafael

    2011-01-01

    Changes in the emission fluorescence intensity of pheophorbide-a (PHEO) in the presence of carboquone (CARBOQ) were used to obtain the association constant, the number of CARBOQ molecules interacting with PHEO, and the fluorescence quantum yield of the complex. Excitation spectra of mixtures of PHEO and CARBOQ in ethanol (EtOH) show an unresolved doublet in the red-most excitation band of PHEO, indicating the formation of a loose ground-state complex. The 1:1 CARBOQ–PHEO complex shows a highe...

  11. On the deduction and analysis of singlet and two-state gating-models from the static structures of mammalian CYP450.

    Science.gov (United States)

    Zawaira, Alexander; Coulson, Lauren; Gallotta, Marco; Karimanzira, Owen; Blackburn, Jonathan

    2011-02-01

    Differential tunnel-opening patterns were established in static structures of mammalian CYP450 isoforms and subsequently applied to identify tunnel-intersecting residues. The identified tunnel-intersecting residues permitted the subsequent construction of gating models via the identification of intra-protein interactions. We define 28 two-state gating models and 37 singlet gating-residue models. Our results reveal the preponderance of aromatic gating residues in CYP3A4 and CYP2A6, whereas we find a preponderance of polar/charged residues in CYP2C5. In CYP2C8 there is balanced presence of polar/charged and hydrophobic aliphatic residues in gating models, whilst in CYP2C9 there is balanced presence of all residue-types. These patterns suggest fast evolutionary dynamics for gating residues and we find that the average rate of evolution of gating residues in CYP2C5, CYP2C8, CYP2C9 and CYP2A6 is significantly faster than the average rate of evolution of the entire sequence. Our study identifies 67% of calculable gating models identified in the literature by molecular dynamics approaches and 92% of residues appearing in literature models appear in our models. However, only 6% of the models identified in this work had been previously-described in the literature. This suggests that our study has defined the most comprehensive list yet of tunnel-gating models in mammalian CYP450 and in doing so have created a benchmark for molecular dynamics approaches to the ligand-tunnelling problem in CYP450. Copyright © 2010 Elsevier Inc. All rights reserved.

  12. A spectroscopic and computational study of the singlet and triplet excited states of synthetic β-functionalized chlorins

    International Nuclear Information System (INIS)

    Brueckner, Christian; McCarthy, Jason R.; Daniell, Heather W.; Pendon, Zeus D.; Ilagan, Robielyn P.; Francis, Tasha M.; Ren Lei; Birge, Robert R.; Frank, Harry A.

    2003-01-01

    This paper presents a comparative investigation of the absorption, fluorescence, electron paramagnetic resonance (EPR), and transient triplet-triplet absorption spectroscopic properties and triplet state dynamics of two functionalized, synthetic, meso-phenylchlorins. The chromophores investigated are the novel 2-hydroxy-3-oxa-5,10,15,20-tetrakisphenylchlorin (3) and the known 2,3-dioxo-5,10,15,20-tetrakisphenylchlorin (4). In these chromophores, one peripheral -CH-CH- bond of the parent porphyrin meso-tetrakisphenylporphyrin (TPP, 1) was formally replaced by a -CH(OH)O- (lactol) or a β-diketone moiety. The spectroscopic data are compared with results from investigations on the parent porphyrin TPP studied here and the parent chlorin 5,10,15,20-tetrakisphenylchlorin (TPC, 2) from the literature. The spectroscopic observables are examined both qualitatively within the framework of the four orbital model and quantitatively using MNDO-PSDCI methods. The results delineate the role of β-lactol and β-dicarbonyl moieties in controlling the electronic and spectroscopic properties of these chromophores. This investigation serves as the foundation from which to derive a general understanding of the effects of β-functionalization on the electronic properties of chlorin-type chromophores. This knowledge is required for the design and understanding of long-wavelength absorbing and fluorescing chromophores to be used in light harvesting systems and photomedicine

  13. Singlets of fermionic gauge symmetries

    NARCIS (Netherlands)

    Bergshoeff, E.A.; Kallosh, R.E.; Rahmanov, M.A.

    1989-01-01

    We investigate under which conditions singlets of fermionic gauge symmetries which are "square roots of gravity" can exist. Their existence is non-trivial because there are no fields neutral in gravity. We tabulate several examples of singlets of global and local supersymmetry and κ-symmetry and

  14. Conformal complex singlet extension of the Standard Model: scenario for dark matter and a second Higgs boson

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhi-Wei; Steele, T.G. [Department of Physics and Engineering Physics, University of Saskatchewan,116 Science Place, Saskatoon, SK, S7N 5E2 (Canada); Hanif, T. [Department of Theoretical Physics, University of Dhaka,Dhaka-1000 (Bangladesh); Mann, R.B. [Department of Physics, University of Waterloo,Waterloo, ON, N2L 3G1 (Canada)

    2016-08-09

    We consider a conformal complex singlet extension of the Standard Model with a Higgs portal interaction. The global U(1) symmetry of the complex singlet can be either broken or unbroken and we study each scenario. In the unbroken case, the global U(1) symmetry protects the complex singlet from decaying, leading to an ideal cold dark matter candidate with approximately 100 GeV mass along with a significant proportion of thermal relic dark matter abundance. In the broken case, we have developed a renormalization-scale optimization technique to significantly narrow the parameter space and in some situations, provide unique predictions for all the model’s couplings and masses. We have found there exists a second Higgs boson with a mass of approximately 550 GeV that mixes with the known 125 GeV Higgs with a large mixing angle sin θ≈0.47 consistent with current experimental limits. The imaginary part of the complex singlet in the broken case could provide axion dark matter for a wide range of models. Upon including interactions of the complex scalar with an additional vector-like fermion, we explore the possibility of a diphoton excess in both the unbroken and the broken cases. In the unbroken case, the model can provide a natural explanation for diphoton excess if extra terms are introduced providing extra contributions to the singlet mass. In the broken case, we find a set of coupling solutions that yield a second Higgs boson of mass 720 GeV and an 830 GeV extra vector-like fermion F, which is able to address the 750 GeV LHC diphoton excess. We also provide criteria to determine the symmetry breaking pattern in both the Higgs and hidden sectors.

  15. Gaugino Mass without Singlets

    CERN Document Server

    Giudice, Gian Francesco; Murayama, H; Rattazzi, Riccardo; Giudice, Gian F.; Luty, Markus A.; Murayama, Hitoshi; Rattazzi, Riccardo

    1998-01-01

    In models with dynamical supersymmetry breaking in the hidden sector, the gaugino masses in the observable sector have been believed to be extremely suppressed (below 1 keV), unless there is a gauge singlet in the hidden sector with specific couplings to the observable sector gauge multiplets. We point out that there is a pure supergravity contribution to gaugino masses at the quantum level arising from the superconformal anomaly. Our results are valid to all orders in perturbation theory and are related to the `exact' beta functions for soft terms. There is also an anomaly contribution to the A terms proportional to the beta function of the corresponding Yukawa coupling. The gaugino masses are proportional to the corresponding gauge beta functions, and so do not satisfy the usual GUT relations.

  16. Influence of an intermolecular charge-transfer state on excited-state relaxation dynamics: solvent effect on the methylnaphthalene-oxygen system and its significance for singlet oxygen production.

    Science.gov (United States)

    Jensen, Poul-Gudmund; Arnbjerg, Jacob; Tolbod, Lars Poulsen; Toftegaard, Rasmus; Ogilby, Peter R

    2009-09-17

    The extent to which an intermolecular charge-transfer (CT) state can influence excited-state relaxation dynamics is examined for the system wherein 1-methylnaphthalene (MN) interacts with molecular oxygen. The MN-O2 system is ideally suited for such a study because excited states can be independently accessed by (i) irradiation into the discrete MN-O2 CT absorption band, (ii) direct irradiation of MN, and (iii) the photosensitized production of triplet state MN. Changing the solvent in which the MN-O2 system is dissolved influences the MN-dependent photoinduced production of singlet oxygen, O2(a1Delta(g)), which, in turn, yields information about fundamental concepts of state mixing. Results of experiments conducted in the polar solvent acetonitrile differ substantially from those obtained from the nonpolar solvent cyclohexane. The data reflect differences in the energy and behavior of the solvent-equilibrated MN-O2 CT state, CT(SE), and the extent to which this state couples to other states of the MN-O2 system. In particular, the data are consistent with a model where both the MN triplet state and the MN-O2 CT(SE) state are immediate precursors of O2(a1Delta(g)). Although the work reported herein is of direct and practical significance for the wide variety of systems in which O2(a1Delta(g)) can be produced upon irradiation, it also serves as an accessible model for a study of general issues pertinent to state mixing and the solvent-dependent dynamics of CT-mediated excited-state relaxation.

  17. Singlet Fission in Rubrene Derivatives: Impact of Molecular Packing

    KAUST Repository

    Sutton, Christopher

    2017-03-13

    We examine the properties of six recently synthesized rubrene derivatives (with substitutions on the side phenyl rings) that show vastly different crystal structures. In order to understand how packing in the solid state affects the excited states and couplings relevant for singlet fission, the lowest excited singlet (S), triplet (T), multiexciton (TT), and charge-transfer (CT) states of the rubrene derivatives are compared to known singlet fission materials [tetracene, pentacene, 5,12-diphenyltetracene (DPT), and rubrene itself]. While a small difference of less than 0.2 eV is calculated for the S and TT energies, a range of 0.50 to 1.2 eV in the CT energies and nearly 3 orders of magnitude in the electronic couplings are computed for the rubrene derivatives in their crystalline packings, which strongly affects the role of the CT state in facilitating SF. To rationalize experimental observations of singlet fission occurring in amorphous phases of rubrene, DPT, and tetracene, we use molecular dynamics (MD) simulations to assess the impact of molecular packing and orientations and to gain a better understanding of the parameters that control singlet fission in amorphous films compared to crystalline packings. The MD simulations point to a crystalline-like packing for thin films of tetracene; on the other hand, DPT, rubrene, and the rubrene derivatives all show various degrees of disorder with a number of sites that have larger electronic couplings than in the crystal, which can facilitate singlet fission in such thin films. Our analysis underlines the potential of these materials as promising candidates for singlet fission and helps understand how various structural motifs affect the critical parameters that control the ability of a system to undergo singlet fission.

  18. Magnetism of singlet - singlet ions interacting with an electron gas: application to PrAl2

    International Nuclear Information System (INIS)

    Palermo, L.

    1986-01-01

    Various magnetic quantities are investigated for a system consisting of singlet-singlet ions interacting with an electron gas. In obtaining the magnetic state equations, the molecular field approximation is used. At T=0, an onset magnetic order condition in function of crystal field and exchange parameters and eletronic density of states at Fermi level is derived. A parametric study of the model is performed numerically. Main results are shown on diagrams. From the experimental data existent in the literature for magnetisation, susceptibility and magnetic specific heat of the PrAl 2 , a fitting with the model predictions is obtained using the following parameters: exchange interaction: 611meV; crystal field parameters: 2,5 meV; band with: 10 eV (of a rectangular density of states with 0,8 el/atom). (author) [pt

  19. Singlet oxygen: photosensitized generation, detection and reaction with organic molecules

    International Nuclear Information System (INIS)

    Barik, Atanu; Indira Priyadarsini, K.; Hari Mohan; Bajaj, P.N.; Sapre, A.V.; Mittal, J.P.; Mukherjee, T.

    2006-10-01

    Singlet molecular oxygen ( 1 O 2 ) is an excited state of molecular oxygen, having antiparallel spin in the same π antibonding orbital. The study of singlet oxygen production and reactivity has emerged as a rich and diverse area, with implication in diverse fields, such as synthetic chemistry, polymer chemistry, photodynamic therapy, etc. There are several known methods to produce singlet oxygen, and also various techniques employed to detect it. Out of these, photosensitization method is the most popular one. In this article, photosensitized production of singlet oxygen from triplet oxygen and photosensitizers in presence of light, and its detection by the infrared luminescence at 1270 nm have been presented. Further, some results using different types of photosensitizers, effect of solvent on singlet oxygen quantum yields and lifetime have been discussed. The quenching rate constants of singlet oxygen have been determined with different types of organic molecules such as derivatives of thiourea and its analogues, hydroxy indoles and antioxidants and the results have been presented. (author)

  20. Search for time-reversal symmetry breaking order at the (1 1 0) interface of YBa{sub 2}Cu{sub 3}O{sub 7-d}elta using betaNMR

    Energy Technology Data Exchange (ETDEWEB)

    Saadaoui, H. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Morris, G.D. [TRIUMF, Wesbrook Mall 4004, Vancouver, British Columbia, V6T 2A3 (Canada); Chow, K.H. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada); Hossain, M.D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Levy, C.D.P. [TRIUMF, Wesbrook Mall 4004, Vancouver, British Columbia, V6T 2A3 (Canada); Parolin, T.J. [Chemistry Department, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Pearson, M.R. [TRIUMF, Wesbrook Mall 4004, Vancouver, British Columbia, V6T 2A3 (Canada); Salman, Z. [Clarendon Laboratory, Department of Physics, Oxford University, Parks Road, Oxford OX1 3PU (United Kingdom); ISIS Facility, Rutherford-Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom); Smadella, M.; Song, Q.; Wang, D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Hentges, P.J.; Greene, L.H. [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Kiefl, R.F. [Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); TRIUMF, Wesbrook Mall 4004, Vancouver, British Columbia, V6T 2A3 (Canada); Canadian Institute for Advanced Research, 180 Dundas Street West, Toronto, Ontario, M5G 1Z8 (Canada); MacFarlane, W.A., E-mail: wam@chem.ubc.c [Chemistry Department, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada)

    2009-04-15

    In this paper, we report initial betaNMR measurements seeking the spontaneous magnetic fields associated with a time-reversal symmetry breaking (TRSB) order at the (1 1 0) interface of the high temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7-d}elta (YBCO). A 2 keV beam of highly spin-polarized {sup 8}Li{sup +} was implanted into a thin overlayer of silver sputtered onto an oriented YBCO film. The NMR of {sup 8}Li in the Ag layer showed additional broadening with an onset below the superconducting transition temperature T{sub c}. This is evidence of spontaneous disordered magnetism which could be associated with TRSB order.

  1. Proton and hydride affinities in excited states: magnitude reversals in proton and hydride affinities between the lowest singlet and triplet states of annulenyl and benzannulenyl anions and cations

    DEFF Research Database (Denmark)

    Rosenberg, Martin; Ottosson, Henrik; Kilså, Kristine

    2010-01-01

    electron counting rules for aromaticity in the two states. Using quantum chemical calculations at the G3(MP2)//(U)B3LYP/6-311+G(d,p) level we have examined the validity of this hypothesis for eight proton and eight hydride addition reactions of anions and cations, respectively, of annulenyl...

  2. One-loop effective Lagrangian for a standard model with a heavy charged scalar singlet

    CERN Document Server

    Bilenky, S M; Bilenky, Mikhail; Santamaria, Arcadi

    1994-01-01

    We study several problems related to the construction and the use of effective Lagrangians by considering an extension of the standard model that includes a heavy scalar singlet coupled to the leptonic doublet. Starting from the full renormalizable model, we build an effective field theory by integrating out the heavy scalar. A local effective Lagrangian (up to operators of dimension six) is obtained by expanding the one-loop effective action in inverse powers of the heavy mass. This is done by matching some Green functions calculated with both the full and the effective theories. Using this simple example we study the renormalization of effective Lagrangians in general and discuss how they can be used to bound new physics. We also discuss the effective Lagrangian after spontaneous symmetry breaking, and the use of the standard model classical equations of motion to rewrite it in different forms. The final effective Lagrangian in the physical basis is well suited to the study of the phenomenology of the model...

  3. Two component WIMP-FImP dark matter model with singlet fermion, scalar and pseudo scalar

    Energy Technology Data Exchange (ETDEWEB)

    Dutta Banik, Amit; Pandey, Madhurima; Majumdar, Debasish [Saha Institute of Nuclear Physics, HBNI, Astroparticle Physics and Cosmology Division, Kolkata (India); Biswas, Anirban [Harish Chandra Research Institute, Allahabad (India)

    2017-10-15

    We explore a two component dark matter model with a fermion and a scalar. In this scenario the Standard Model (SM) is extended by a fermion, a scalar and an additional pseudo scalar. The fermionic component is assumed to have a global U(1){sub DM} and interacts with the pseudo scalar via Yukawa interaction while a Z{sub 2} symmetry is imposed on the other component - the scalar. These ensure the stability of both dark matter components. Although the Lagrangian of the present model is CP conserving, the CP symmetry breaks spontaneously when the pseudo scalar acquires a vacuum expectation value (VEV). The scalar component of the dark matter in the present model also develops a VEV on spontaneous breaking of the Z{sub 2} symmetry. Thus the various interactions of the dark sector and the SM sector occur through the mixing of the SM like Higgs boson, the pseudo scalar Higgs like boson and the singlet scalar boson. We show that the observed gamma ray excess from the Galactic Centre as well as the 3.55 keV X-ray line from Perseus, Andromeda etc. can be simultaneously explained in the present two component dark matter model and the dark matter self interaction is found to be an order of magnitude smaller than the upper limit estimated from the observational results. (orig.)

  4. New strategies to produce and detect singlet oxygen in a cell

    DEFF Research Database (Denmark)

    Gollmer, Anita

    2012-01-01

    product of the reaction between SOSG and singlet oxygen is itself an efficient singlet oxygen sensitizer and, second, that despite published claims to the contrary, SOSG can, in fact, be incorporated into living mammalian cells. Further, a new fluorescent probe for singlet oxygen called “Aarhus Green...... to achieve a reproducible assessment of cell response to a controlled dose of singlet oxygen produced in a spatially-localized two-photon sensitized experiment. Different assays were used to visualize cell response. In this dissertation, various aspects of fluorescence imaging and two-photon excitation......Singlet oxygen, the first excited electronic state of molecular oxygen, plays a major role in oxygen-dependent photo-induced cell death. In such systems, singlet oxygen is generally produced in a photosensitized process wherein light is absorbed by a molecule (the so-called sensitizer) which...

  5. Toward Singlet-Triplet Bistable Nonalternant Kekulé Hydrocarbons: Azulene-to-Naphthalene Rearrangement.

    Science.gov (United States)

    Das, Soumyajit; Wu, Jishan

    2015-12-04

    Recent developments of open-shell singlet diradicaloids motivated the search for stable singlet-triplet bistable nonalternant polycyclic hydrocarbons. During the synthesis of this type of molecule, such as the dibenzo-cyclohepta[def]fluorene 3, an unexpected azulene-to-naphthalene rearrangement was observed at room temperature, which resulted in new nonalternant hydrocarbons 8a/8b with a closed-shell singlet ground state. These studies provided insight into the unique chemistry of azulene and challenges for the synthesis of singlet-triplet bistable polycyclic hydrocarbons.

  6. A Comparison of Singlet Oxygen Explicit Dosimetry (SOED and Singlet Oxygen Luminescence Dosimetry (SOLD for Photofrin-Mediated Photodynamic Therapy

    Directory of Open Access Journals (Sweden)

    Michele M. Kim

    2016-12-01

    Full Text Available Accurate photodynamic therapy (PDT dosimetry is critical for the use of PDT in the treatment of malignant and nonmalignant localized diseases. A singlet oxygen explicit dosimetry (SOED model has been developed for in vivo purposes. It involves the measurement of the key components in PDT—light fluence (rate, photosensitizer concentration, and ground-state oxygen concentration ([3O2]—to calculate the amount of reacted singlet oxygen ([1O2]rx, the main cytotoxic component in type II PDT. Experiments were performed in phantoms with the photosensitizer Photofrin and in solution using phosphorescence-based singlet oxygen luminescence dosimetry (SOLD to validate the SOED model. Oxygen concentration and photosensitizer photobleaching versus time were measured during PDT, along with direct SOLD measurements of singlet oxygen and triplet state lifetime (τΔ and τt, for various photosensitizer concentrations to determine necessary photophysical parameters. SOLD-determined cumulative [1O2]rx was compared to SOED-calculated [1O2]rx for various photosensitizer concentrations to show a clear correlation between the two methods. This illustrates that explicit dosimetry can be used when phosphorescence-based dosimetry is not feasible. Using SOED modeling, we have also shown evidence that SOLD-measured [1O2]rx using a 523 nm pulsed laser can be used to correlate to singlet oxygen generated by a 630 nm laser during a clinical malignant pleural mesothelioma (MPM PDT protocol by using a conversion formula.

  7. Bifurcation in Ground-state Fidelity and Quantum Criticality in Two-leg Potts Ladder

    Directory of Open Access Journals (Sweden)

    Sheng-Hao LI

    2014-02-01

    Full Text Available We have investigated an intriguing connection between bifurcations, reduced fidelity per lattice site, local order parameter, universal order parameter, entropy and quantum phase transitions in the ground state for quantum three-state Potts model with two coupled infinite-size ladder system, in the context of the tensor network algorithm. The tensor network algorithm produces degenerate symmetry-breaking ground-state wave functions arising from the Z3 symmetry breaking, each of results from a randomly chosen initial state. We expect that our approach might provide further insights into critical phenomena in quantum many-body infinite lattice systems in condensed matter physics.

  8. Symmetry breaking and electrical conductivity of La0.7Sr0.3Cr0.4Mn0.6O3-δ perovskite as SOFC anode material

    International Nuclear Information System (INIS)

    Reyes-Rojas, A.; Alvarado-Flores, J.; Esparza-Ponce, H.; Esneider-Alcala, M.; Espitia-Cabrera, I.; Torres-Moye, E.

    2011-01-01

    Research highlights: → Perovskite-type La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ -NiO nucleation kinetics. Symmetry-breaking by introducing Ni 2+ cations at 1050 deg. C. Phase transition from high temperature aristotype R3-bar c to hettotype I4/mmm. At low Ni concentration ρ resistivity decreases when increasing the temperature. For Ni concentration higher than 25% ρ resistivity increases. - Abstract: This work is focused on nanocrystalline solid oxide fuel cell synthesis and characterization (SOFC) anodes of La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ (perovskite-type) with Nickel. Perovskite-type oxide chemical reactivity, nucleation kinetics and phase composition related with La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ -NiO to La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ -Ni transformation have been analyzed. SOFC anode powders were obtained by sol-gel synthesis, using polyvinyl alcohol as an organic precursor to get a porous cermet electrode after sintering at 1365 deg. C and oxide reduction by hydrogen at 800 deg. C/1050 deg. C for 8 h in a horizontal tubular reactor furnace under 10% H 2 /N 2 atmosphere. Composite powders were compressed into 10-mm diameter discs with 25-75 wt% Ni. Electrical and structural characterization by four-point probe method for conductivity, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Rietveld method were carried out. Symmetry-breaking by phase transition from high temperature aristotype R3-bar c to hettotype I4/mmm has been identified and confirmed by XRD and Rietveld method which can be produced by introducing Ni 2+ cations in the perovskite solid solution. Rietveld analysis suggests that Ni contents are directly proportional to La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 NiO 3.95 tetragonal structure cell volume and inversely proportional to Ni cubic structure cell volume after reduction at 1050 deg. C. Kinetic analysis indicated that the Johnson-Mehl-Avrami equation is able to provide a good fit to phase

  9. Is π-Stacking Prone To Accelerate Singlet-Singlet Energy Transfers?

    Science.gov (United States)

    Gao, Di; Aly, Shawkat M; Karsenti, Paul-Ludovic; Harvey, Pierre D

    2018-03-23

    π-Stacking is the most common structural feature that dictates the optical and electronic properties of chromophores in the solid state. Herein, a unidirectional singlet-singlet energy-transfer dyad has been designed to test the effect of π-stacking of zinc(II) porphyrin, [Zn 2 ], as a slipped dimer acceptor using a BODIPY unit, [bod], as the donor, bridged by the linker C 6 H 4 C≡CC 6 H 4 . The rate of singlet energy transfer, k ET (S 1 ), at 298 K ( k ET (S 1 ) = 4.5 × 10 10 s -1 ) extracted through the change in fluorescence lifetime, τ F , of [bod] in the presence (27.1 ps) and the absence of [Zn 2 ] (4.61 ns) from Streak camera measurements, and the rise time of the acceptor signal in femtosecond transient absorption spectra (22.0 ps), is faster than most literature cases where no π-stacking effect exists (i.e., monoporphyrin units). At 77 K, the τ F of [bod] increases to 45.3 ps, indicating that k ET (S 1 ) decreases by 2-fold (2.2 × 10 10 s -1 ), a value similar to most values reported in the literature, thus suggesting that the higher value at 298 K is thermally promoted at a higher temperature.

  10. Impurities near an antiferromagnetic-singlet quantum critical point

    International Nuclear Information System (INIS)

    Mendes-Santos, T.; Costa, N. C.; Batrouni, G.

    2017-01-01

    Heavy-fermion systems and other strongly correlated electron materials often exhibit a competition between antiferromagnetic (AF) and singlet ground states. We examine the effect of impurities in the vicinity of such an AF-singlet quantum critical point (QCP), through an appropriately defined “impurity susceptibility” χimp, using exact quantum Monte Carlo simulations. Our key finding is a connection within a single calculational framework between AF domains induced on the singlet side of the transition and the behavior of the nuclear magnetic resonance (NMR) relaxation rate 1/T1. Furthermore, we show that local NMR measurements provide a diagnostic for the location of the QCP, which agrees remarkably well with the vanishing of the AF order parameter and large values of χimp.

  11. Explorative computational study of the singlet fission process

    NARCIS (Netherlands)

    Havenith, Remco W. A.; de Gier, Hilde D.; Broer, Ria

    2012-01-01

    Different ab initio methods, namely multi-reference and nonorthogonal configuration interaction techniques, are explored for their applicability in studying the singlet fission problem. It has been shown for 2-methyl-1,5-hexadiene that the (TT)-T-1 state can be identified using multi-reference

  12. Chimera states in a population of identical oscillators under planar ...

    Indian Academy of Sciences (India)

    Abstract. We report the existence of chimera states in an assembly of identical nonlinear oscil- lators that are globally linked to each other in a simple planar cross-coupled form. The rotational symmetry breaking of the coupling term appears to be responsible for the emergence of these col- lective states that display a ...

  13. Top-antitop production from W{sup +}{sub L}W{sup -}{sub L} and Z{sub L}Z{sub L} scattering under a strongly interacting symmetry-breaking sector

    Energy Technology Data Exchange (ETDEWEB)

    Castillo, Andres [Universidad Nacional de Colombia, Sede Bogota, Departamento de Fisica, Facultad de Ciencias, Bogota (Colombia); Delgado, Rafael L.; Dobado, Antonio; Llanes-Estrada, Felipe J. [Universidad Complutense de Madrid, Departamento de Fisica Teorica I, Madrid (Spain)

    2017-07-15

    By considering a non-linear electroweak chiral Lagrangian, including the Higgs, coupled to heavy quarks, and the equivalence theorem, we compute the one-loop scattering amplitudes W{sup +}W{sup -} → t anti t, ZZ → t anti t and hh → t anti t (in the regime M{sub t}{sup 2}/v{sup 2} << √(s)M{sub t}/v{sup 2} << s/v{sup 2} and to NLO in the effective theory). We calculate the scalar partial-wave helicity amplitudes which allow us to check unitarity at the perturbative level in both M{sub t}/v and s/v. As with growing energy perturbative unitarity deteriorates, we also introduce a new unitarization method with the right analytical behavior on the complex s-plane and that can support poles on the second Riemann sheet to describe resonances in terms of the Lagrangian couplings. Thus we have achieved a consistent phenomenological description of any resonant t anti t production that may be enhanced by a possible strongly interacting electroweak symmetry breaking sector. (orig.)

  14. Singlet-triplet annihilation in single LHCII complexes.

    Science.gov (United States)

    Gruber, J Michael; Chmeliov, Jevgenij; Krüger, Tjaart P J; Valkunas, Leonas; van Grondelle, Rienk

    2015-08-14

    In light harvesting complex II (LHCII) of higher plants and green algae, carotenoids (Cars) have an important function to quench chlorophyll (Chl) triplet states and therefore avoid the production of harmful singlet oxygen. The resulting Car triplet states lead to a non-linear self-quenching mechanism called singlet-triplet (S-T) annihilation that strongly depends on the excitation density. In this work we investigated the fluorescence decay kinetics of single immobilized LHCIIs at room temperature and found a two-exponential decay with a slow (3.5 ns) and a fast (35 ps) component. The relative amplitude fraction of the fast component increases with increasing excitation intensity, and the resulting decrease in the fluorescence quantum yield suggests annihilation effects. Modulation of the excitation pattern by means of an acousto-optic modulator (AOM) furthermore allowed us to resolve the time-dependent accumulation and decay rate (∼7 μs) of the quenching species. Inspired by singlet-singlet (S-S) annihilation studies, we developed a stochastic model and then successfully applied it to describe and explain all the experimentally observed steady-state and time-dependent kinetics. That allowed us to distinctively identify the quenching mechanism as S-T annihilation. Quantitative fitting resulted in a conclusive set of parameters validating our interpretation of the experimental results. The obtained stochastic model can be generalized to describe S-T annihilation in small molecular aggregates where the equilibration time of excitations is much faster than the annihilation-free singlet excited state lifetime.

  15. Photo-excitation of carotenoids causes cytotoxicity via singlet oxygen production

    International Nuclear Information System (INIS)

    Yoshii, Hiroshi; Yoshii, Yukie; Asai, Tatsuya; Furukawa, Takako; Takaichi, Shinichi; Fujibayashi, Yasuhisa

    2012-01-01

    Highlights: ► Some photo-excited carotenoids have photosensitizing ability. ► They are able to produce ROS. ► Photo-excited fucoxanthin can produce singlet oxygen through energy transfer. -- Abstract: Carotenoids, natural pigments widely distributed in algae and plants, have a conjugated double bond system. Their excitation energies are correlated with conjugation length. We hypothesized that carotenoids whose energy states are above the singlet excited state of oxygen (singlet oxygen) would possess photosensitizing properties. Here, we demonstrated that human skin melanoma (A375) cells are damaged through the photo-excitation of several carotenoids (neoxanthin, fucoxanthin and siphonaxanthin). In contrast, photo-excitation of carotenoids that possess energy states below that of singlet oxygen, such as β-carotene, lutein, loroxanthin and violaxanthin, did not enhance cell death. Production of reactive oxygen species (ROS) by photo-excited fucoxanthin or neoxanthin was confirmed using a reporter assay for ROS production with HeLa Hyper cells, which express a fluorescent indicator protein for intracellular ROS. Fucoxanthin and neoxanthin also showed high cellular penetration and retention. Electron spin resonance spectra using 2,2,6,6-tetramethil-4-piperidone as a singlet oxygen trapping agent demonstrated that singlet oxygen was produced via energy transfer from photo-excited fucoxanthin to oxygen molecules. These results suggest that carotenoids such as fucoxanthin, which are capable of singlet oxygen production through photo-excitation and show good penetration and retention in target cells, are useful as photosensitizers in photodynamic therapy for skin disease.

  16. Chimera states in a population of identical oscillators under planar ...

    Indian Academy of Sciences (India)

    2015-01-30

    Jan 30, 2015 ... The rotational symmetry breaking of the coupling term appears to be responsible for the emergence of these collective states that display a characteristic coexistence of coherent and incoherent behaviour. The finding, observed in both a collection of van der Pol oscillators and chaotic Rössler oscillators, ...

  17. Experimental search of the electroweak symmetry breaking in the H→γγ channel and of a solution to the hierarchy problem in ATLAS. Participation to the preparation of the electronics of the electromagnetic calorimeter

    International Nuclear Information System (INIS)

    Escalier, Marc

    2005-01-01

    This thesis deals with the understanding of the spontaneous electroweak symmetry breaking mechanism in the ATLAS experiment at LHC collider, by studying two complementary topics: the search for the Higgs boson in the H→γγ channel, and a search for extra dimensions in the gluon sector. Tests of the electronic of the electromagnetic calorimeter allowed to validate various cards that were under the responsibility of the LPNHE. Using full simulation data of the detector allowed us to precisely compute mass resolution of the di-photon system. Due to recent theoretical improvements, signal and background have been studied at the next order of the perturbative development, which increases cross-sections. With regards to the jet background, a study has been done using discriminating variables in order to obtain, for a 80 % photons efficiency, a rejection factor of 7000. The discovery potential benefits from this change of cross-sections and increases by 50 % in comparison with the same analysis done at the leading order. In addition to this, a new analysis using a maximum likelihood method allowed us to increase by 40 % the discovery potential in comparison with our classical analysis. In conclusion, the Higgs boson of 120 GeV/c 2 can be now discovered in this channel with an integrated luminosity of 10 fb -1 . Furthermore, naturality problem of the Higgs boson mass can be solved by introducing extra dimensions in which gluons can propagate. We have shown that it was possible to discover extra-dimensions up to a compactification scale of 15 TeV. (author)

  18. Experiment search of the electroweak symmetry breaking in the H → γγ channel and of a solution of the hierarchy problem in the Atlas experiment: participation to the tests of the electronics of the electromagnetic calorimeter

    International Nuclear Information System (INIS)

    Escalier, M.

    2005-04-01

    This thesis deals with the understanding of the spontaneous electroweak symmetry breaking mechanism in the ATLAS experiment at LHC collider, by studying two complementary topics: the search for the Higgs boson in the H → γγ channel, and a search for extra dimensions in the gluon sector. Tests of the electronic of the electromagnetic calorimeter allowed us to validate various cards that were under the responsibility of the LPNHE. Using full simulation data of the detector allowed us to precisely compute mass resolution of the di-photon system. Due to recent theoretical improvements, signal and background have been studied at the next order of the perturbative development, which increases cross-sections. With regards to the jet background, a study has been done using discriminating variables in order to obtain, for a 80 % photons efficiency, a rejection factor of 7000. The discovery potential benefits from this change of cross-sections and increases by 50 % in comparison with the same analysis done at the leading order. In addition to this, a new analysis using a maximum likelihood method allowed us to increase by 40 % the discovery potential in comparison with our classical analysis. In conclusion, the Higgs boson of 120 GeV/c 2 can be now discovered in this channel with an integrated luminosity of 10 fb -1 . Furthermore, the consistency of the problem of the Higgs boson mass can be solved by introducing extra dimensions in which gluons can propagate. We have shown that it was possible to discover extra-dimensions up to a compactification scale of 15 TeV. (author)

  19. Formulation of the low-energy effective theory of electroweak symmetry-breaking without a Higgs particle; Formulation de la theorie effective a basse energie du secteur electrofaible sans particule de Higgs

    Energy Technology Data Exchange (ETDEWEB)

    Hirn, J

    2004-07-01

    The low-energy effective theory of electroweak symmetry-breaking without a Higgs particle is constructed using the methods of Chiral Perturbation Theory. Weinberg's power-counting formula demonstrates the consistency of the loop expansion, with the corresponding renormalization. We find that the suppression of effective operators by a mass scale, which was automatic in the case of the Standard Model, no longer holds in the Higgs-less case. Moreover, the incriminated operators appear at leading order in the chiral expansion, at variance with experiments. To account for their suppression, invariance under a larger symmetry is required, corresponding to the composite sector (which produces the three Goldstone modes) being decoupled from the elementary sector (quarks, leptons and Yang-Mills fields). The couplings are introduced via spurions: this reduces the symmetry to SU(2) x U(1). In the simultaneous expansion in powers of momenta and spurions, the aforementioned operators are relegated to higher orders. In addition, the method allows for a systematic treatment of weak isospin breaking. The Weinberg power-counting formula can be recovered, and small neutrino masses accounted for. The three right-handed neutrinos (lighter than the TeV), which are introduced in connection with the custodial symmetry, are quasi-sterile and stable. A constraint on the underlying theory is obtained by studying the anomaly-matching in the composite sector and generalizing the Wess-Zumino construction. The spurion formalism is also applied to open linear moose models, for which generalized Weinberg sum rules are derived. (author)

  20. Flavor-singlet spectrum in multi-flavor QCD

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, Yasamichi; Rinaldi, Enrico

    2017-06-18

    Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.

  1. Singlet oxygen reactions with flavonoids. A theoretical-experimental study.

    Directory of Open Access Journals (Sweden)

    Javier Morales

    Full Text Available Detection of singlet oxygen emission, λ(max = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T, and the reactive reaction rate constant, k(r, for the reaction between singlet oxygen and several flavonoids. Values of k(T determined in deuterated water, ranging from 2.4×10(7 M(-1 s(-1 to 13.4×10(7 M(-1 s(-1, for rutin and morin, respectively, and the values measured for k(r, ranging from 2.8×10(5 M(-1 s(-1 to 65.7×10(5 M(-1 s(-1 for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

  2. Singlet oxygen reactions with flavonoids. A theoretical-experimental study.

    Science.gov (United States)

    Morales, Javier; Günther, Germán; Zanocco, Antonio L; Lemp, Else

    2012-01-01

    Detection of singlet oxygen emission, λ(max) = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, k(T), and the reactive reaction rate constant, k(r), for the reaction between singlet oxygen and several flavonoids. Values of k(T) determined in deuterated water, ranging from 2.4×10(7) M(-1) s(-1) to 13.4×10(7) M(-1) s(-1), for rutin and morin, respectively, and the values measured for k(r), ranging from 2.8×10(5) M(-1) s(-1) to 65.7×10(5) M(-1) s(-1) for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

  3. Flavor-singlet spectrum in multi-flavor QCD

    Science.gov (United States)

    Aoki, Yasumichi; Aoyama, Tatsumi; Bennett, Ed; Kurachi, Masafumi; Maskawa, Toshihide; Miura, Kohtaroh; Nagai, Kei-ichi; Ohki, Hiroshi; Rinaldi, Enrico; Shibata, Akihiro; Yamawaki, Koichi; Yamazaki, Takeshi

    2018-03-01

    Studying SU(3) gauge theories with increasing number of light fermions is relevant both for understanding the strong dynamics of QCD and for constructing strongly interacting extensions of the Standard Model (e.g. UV completions of composite Higgs models). In order to contrast these many-flavors strongly interacting theories with QCD, we study the flavor-singlet spectrum as an interesting probe. In fact, some composite Higgs models require the Higgs boson to be the lightest flavor-singlet scalar in the spectrum of a strongly interacting new sector with a well defined hierarchy with the rest of the states. Moreover, introducing many light flavors at fixed number of colors can influence the dynamics of the lightest flavor-singlet pseudoscalar. We present the on-going study of these flavor-singlet channels using multiple interpolating operators on high-statistics ensembles generated by the LatKMI collaboration and we compare results with available data obtained by the Lattice Strong Dynamics collaboration. For the theory with 8 flavors, the two collaborations have generated configurations that complement each others with the aim to tackle the massless limit using the largest possible volumes.

  4. Symmetry breaking during seeded growth of nanocrystals.

    Science.gov (United States)

    Xia, Xiaohu; Xia, Younan

    2012-11-14

    Currently, most of the reported noble-metal nanocrystals are limited to a high level of symmetry, as constrained by the inherent, face-centered cubic (fcc) lattice of these metals. In this paper, we report, for the first time, a facile and versatile approach (backed up by a clear mechanistic understanding) for breaking the symmetry of an fcc lattice and thus obtaining nanocrystals with highly unsymmetrical shapes. The key strategy is to induce and direct the growth of nanocrystal seeds into unsymmetrical modes by manipulating the reduction kinetics. With silver as an example, we demonstrated that the diversity of possible shapes taken by noble-metal nanocrystals could be greatly expanded by incorporating a series of new shapes drastically deviated from the fcc lattice. This work provides a new method to investigate shape-controlled synthesis of metal nanocrystal.

  5. Higgsless approach to electroweak symmetry breaking

    CERN Document Server

    Grojean, Christophe

    2007-01-01

    Higgsless models are an attempt to achieve a breaking of the electroweak symmetry via boundary conditions at the end-points of a fifth dimension compactified on an interval, as an alternative to the usual Higgs mechanism. There is no physical Higgs scalar in the spectrum and the perturbative unitarity violation scale is delayed via the exchange of massive spin-1 KK resonances. The correct mass spectrum is reproduced in a model in warped space, which inherits a custodial symmetry from a left–right gauge symmetry in the bulk. Phenomenological challenges as well as collider signatures are presented. From the AdS/CFT perspective, this model appears as a weakly coupled dual to walking technicolour models.

  6. Symmetry Breaking in Few Layer Graphene Films

    Energy Technology Data Exchange (ETDEWEB)

    Bostwick, A.; Ohta, T.; McChesney, J.L.; Emtsev, K.; Seyller,Th.; Horn, K.; Rotenberg, E.

    2007-05-25

    Recently, it was demonstrated that the quasiparticledynamics, the layer-dependent charge and potential, and the c-axisscreening coefficient could be extracted from measurements of thespectral function of few layer graphene films grown epitaxially on SiCusing angle-resolved photoemission spectroscopy (ARPES). In this articlewe review these findings, and present detailed methodology for extractingsuch parameters from ARPES. We also present detailed arguments againstthe possibility of an energy gap at the Dirac crossing ED.

  7. Electroweak symmetry breaking beyond the Standard Model

    Indian Academy of Sciences (India)

    . ... Figure 1. Cancellation of quadratic divergence to scalar mass-square between fermion and boson loops. (3) The SM is plagued by the hierarchy problem. ..... action should be un-suppressed, where gSM is a gauge or Yukawa coupling.

  8. Lorentz Symmetry Breaking in Quantum Electrodynamics

    OpenAIRE

    Oliveira, D. M.

    2010-01-01

    In this dissertation, we study the implications generated by the Lorentz breaking symmetry in quantum electrodynamics. We analyze fermions interacting with an electromagnetic field in the contexts of quantum mechanics and make radiative corrections. In quantum mechanics, the terms of the Lorentz breaking symmetry were treated as perturbations to the Dirac equation, and their expected values were obtained in a vacuum. In the radiative corrections, the Lorentz breaking symmetry was introduced i...

  9. Symmetry and symmetry breaking in quantum mechanics

    International Nuclear Information System (INIS)

    Chomaz, Philippe

    1998-01-01

    In the world of infinitely small, the world of atoms, nuclei and particles, the quantum mechanics enforces its laws. The discovery of Quanta, this unbelievable castration of the Possible in grains of matter and radiation, in discrete energy levels compels us of thinking the Single to comprehend the Universal. Quantum Numbers, magic Numbers and Numbers sign the wave. The matter is vibration. To describe the music of the world one needs keys, measures, notes, rules and partition: one needs quantum mechanics. The particles reduce themselves not in material points as the scholars of the past centuries thought, but they must be conceived throughout the space, in the accomplishment of shapes of volumes. When Einstein asked himself whether God plays dice, there was no doubt among its contemporaries that if He exists He is a geometer. In a Nature reduced to Geometry, the symmetries assume their role in servicing the Harmony. The symmetries allow ordering the energy levels to make them understandable. They impose there geometrical rules to the matter waves, giving them properties which sometimes astonish us. Hidden symmetries, internal symmetries and newly conceived symmetries have to be adopted subsequently to the observation of some order in this world of Quanta. In turn, the symmetries provide new observables which open new spaces of observation

  10. Bilocal functional approach to dynamical symmetry breaking

    International Nuclear Information System (INIS)

    Ebert, D.; Pervushin, V.N.

    1977-01-01

    The Abelian gauge theory of massless fermions (''quarks'') interacting with a massless neutral vector (''gluon'') field is considered. The Green two-particle functions of the quarks and vector gluons are computed. The graphical expression of the bilocal propagator and that of different terms in the expansion of path integrals for these functions are given

  11. Spontaneous symmetry breaking: formation of Janus micelles

    NARCIS (Netherlands)

    Voets, I.K.; Fokkink, R.G.; Hellweg, T.; King, S.M.; Waard, de P.; Keizer, de A.; Cohen Stuart, M.A.

    2009-01-01

    We describe the preparation and solution properties of Janus micelles, i.e., non-centrosymmetric nanoparticles with compartmentalized shells, via co-assembly of two fully water-soluble block copolymers. They consist of a mixed core of poly(N-methyl-2-vinyl pyridinium iodide) (P2MVP) and poly(acrylic

  12. Cracking up: symmetry breaking in cellular systems

    Science.gov (United States)

    Paluch, Ewa; van der Gucht, Jasper; Sykes, Cécile

    2006-01-01

    The shape of animal cells is, to a large extent, determined by the cortical actin network that underlies the cell membrane. Because of the presence of myosin motors, the actin cortex is under tension, and local relaxation of this tension can result in cortical flows that lead to deformation and polarization of the cell. Cortex relaxation is often regulated by polarizing signals, but the cortex can also rupture and relax spontaneously. A similar tension-induced polarization is observed in actin gels growing around beads, and we propose that a common mechanism governs actin gel rupture in both systems. PMID:17145960

  13. Electroweak symmetry breaking beyond the Standard Model

    Indian Academy of Sciences (India)

    potential: V = −. (gSM)4. 16π2 f 2 ln. ( 2 f 2. ) (H† H) + g2. SM(H† H)2 ,. (11). i.e., the bilinear term should have a one-loop suppression but, crucially, the quartic inter- action should be un-suppressed, where gSM is a gauge or Yukawa coupling. If both quadratic and quartic terms are suppressed, one cannot simultaneously ...

  14. Discrete symmetry breaking beyond the standard model

    NARCIS (Netherlands)

    Dekens, Wouter Gerard

    2015-01-01

    The current knowledge of elementary particles and their interactions is summarized in the Standard Model of particle physics. Practically all the predictions of this model, that have been tested, were confirmed experimentally. Nonetheless, there are phenomena which the model cannot explain. For

  15. Internal Einstein spaces and symmetry breaking

    International Nuclear Information System (INIS)

    Coquereaux, R.

    1984-01-01

    We first define a generalised gauge invariant Yang-Mills Lagrangian: the Killing metric -Ksub(αβ) on the group is replaced by a more general metric hsub(αβ)(x); the field hsub(αβ)(x) -a scalar from the space time point of view- is then covariantly coupled to the gauge field Asub(μ)sup(α) and is also self-coupled via a natural scalar potential (no parameters). Non trivial saddle points of this scalar potential, correspond to non standard Einstein metrics on the group C. the associated shifts lead to an entirely computable mass spectrum for the gauge field

  16. Wilson-loop symmetry breaking reexamined

    International Nuclear Information System (INIS)

    Nakamura, A.; Shiraishi, K.

    1988-07-01

    The splitting in the energy of gauge field vacua on non-simply connected space S 3 /Z 2 is reconsidered. We show the calculation to the one-loop level for a Yang-Mills vector with a ghost field. We confirm our previous result and give a solution to the question offered by Freire, Romao and Barroso. (author)

  17. Magnetic rotation and chiral symmetry breaking

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 57; Issue 2-3 ... Most of the symmetry operations considered so far have been defined for a situation wherein the angular momentum coincides with one of the principal axes and ... The total angular momentum vector in such bands is tilted away from the principal axes.

  18. Cilia in Left-Right Symmetry Breaking.

    Science.gov (United States)

    Shinohara, Kyosuke; Hamada, Hiroshi

    2017-10-03

    Visceral organs of vertebrates show left-right (L-R) asymmetry with regard to their position and morphology. Cilia play essential role in generating L-R asymmetry. A number of genes required for L-R asymmetry have now been identified in vertebrates, including human, many of which contribute to the formation and motility of cilia. In the mouse embryo, breaking of L-R symmetry occurs in the ventral node, where two types of cilia (motile and immotile) are present. Motile cilia are located at the central region of the node, and generate a leftward fluid flow. These motile cilia at the node are unique in that they rotate in the clockwise direction, unlike other immotile cilia such as airway cilia that show planar beating. The second type of cilia essential for L-R asymmetry is immotile cilia that are peripherally located immotile cilia. They sense a flow-dependent signal, which is either chemical or mechanical in nature. Although Ca 2+ signaling is implicated in flow sensing, the precise mechanism remains unknown. Copyright © 2017 Cold Spring Harbor Laboratory Press; all rights reserved.

  19. Chiral symmetry breaking in finite quantum electrodynamics

    International Nuclear Information System (INIS)

    Montero, J.C.; Pleitez, V.

    1987-01-01

    The dynamical breakdown of chiral symmetry in a finite Abelian gauge theory using a variational approach for the effective potential for composite operators is discussed. It is shown that, at least in a variational approach, the fermion either remains massless or gets a dynamical mass for every non-zero coupling constant. (Author) [pt

  20. Flavor-singlet hidden charm pentaquark

    Science.gov (United States)

    Irie, Yoya; Oka, Makoto; Yasui, Shigehiro

    2018-02-01

    One type of hidden charm pentaquark Pc s with quark content c c ¯u d s in light-flavor singlet state is studied in the quark model. This state is analogous to the Pc with c c ¯u u d in light-flavor octet, which was observed in LHC in 2015. Considering various combinations of color, spin, and light flavor as internal quantum numbers in Pc s, we investigate the mass ordering of the Pc s's by adopting both the one-gluon exchange interaction and the instanton-induced interaction in the quark model. The most stable configuration of Pc s is identified to be total spin 1 /2 in which the c c ¯ is combined to be color octet and spin 1, while the u d s cluster is in a color octet state. The other color octet configurations, the total spin 1 /2 state with the c c ¯ spin 0, and the state with total spin 3 /2 and c c ¯ spin 1, are found as excited states. We also discuss possible decay modes of these hidden charm pentaquarks.