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Sample records for s-wave gap symmetry

  1. Single gap s-wave superconductivity in Nb{sub 2}PdS{sub 5}

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    Shruti [School of Physical Sciences, JNU, New Delhi (India); Goyal, R.; Awana, V.P.S. [CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012 (India); Patnaik, S., E-mail: spatnaik@mail.jnu.ac.in [School of Physical Sciences, JNU, New Delhi (India)

    2016-05-15

    Highlights: • In this paper, we report on pairing symmetry and superconducting gap in recently discovered superconductor Nb2PdS5. • This is a remarkable superconductor with highest ever reported Hc2/Tc ratio of ∼3. • In some theoretical studies, such effects have been ascribed to multiband effects and possible p-wave superconductivity. • However our penetration depth data is well ascribed to a single gap nodeless S-wave superconductivity. - Abstract: Superconducting order parameter and its symmetry are important parameters towards deciphering the pairing mechanism in newly discovered superconducting systems. We report a study on penetration depth measurement on Nb{sub 2}PdS{sub 5} that has recently been reported with extremely high upper critical field with possible triplet pairing mechanism. Our data show that at low temperatures the change in penetration depth Δλ is best fitted with BCS s-wave model for single gap with zero-temperature value of the superconducting energy gap Δ{sub 0} = 1.05 meV, corresponding to the ratio 2Δ{sub 0}/k{sub B}T{sub c} = 3.9 ± 0.18. The superfluid density in the entire temperature range is well described by single gap with gap ratio 2Δ{sub 0}/k{sub B}T{sub c} = 4.1 ± 0.13 for λ(0) = 225 nm.

  2. 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.

  3. Symmetry reduction and boundary modes for Fe chains on an s-wave superconductor.

    Science.gov (United States)

    Chen, Yu-Qin; Wu, Yi-Ming; Liu, Xiong-Jun

    2016-11-30

    We investigate the superconducting phases and boundary modes for a quasi-1D system formed by up to three Fe chains on an s-wave superconductor, motivated by a recent experiment. While the Rashba type spin-orbit coupling together with a magnetic ordering is necessary to drive the system to be of nontrivial topology, we show that the onsite [Formula: see text] spin-orbit term, inter-chain diagonal hopping couplings, and magnetic disorders in the Fe chains are crucial in determining the symmetry classes of superconducting phases, which can be topologically trivial or nontrivial in different parameter regimes. In general multiple low-energy Andreev bound states, as well as a single Majorana zero mode if the phase is topological, are obtained in the ends of Fe chains. The nontrivial symmetry reduction mechanism is uncovered to provide an understanding of the present results, and may explain the zero-bias peak observed in the experiment. The present study can be applied to generic multiple-chain system.

  4. s-wave charmed baryon resonances from a coupled-channel approach with heavy quark symmetry

    NARCIS (Netherlands)

    Garcia-Recio, C.; Magas, V. K.; Mizutani, T.; Nieves, J.; Ramos, A.; Salcedo, L. L.; Tolos, L.

    We study charmed baryon resonances that are generated dynamically within a unitary meson-baryon coupled-channel model that treats the heavy pseudoscalar and vector mesons on equal footing as required by heavy-quark symmetry. It is an extension of recent SU(4) models with t-channel vector-meson

  5. Using gap symmetry and structure to reveal the pairing mechanism in Fe-based superconductors

    Science.gov (United States)

    Hirschfeld, Peter J.

    2016-01-01

    I review theoretical ideas and implications of experiments for the gap structure and symmetry of the Fe-based superconductors. Unlike any other class of unconventional superconductors, one has in these systems the possibility to tune the interactions by small changes in pressure, doping or disorder. Thus, measurements of order parameter evolution with these parameters should enable a deeper understanding of the underlying interactions. I briefly review the ;standard paradigm; for s-wave pairing in these systems, and then focus on developments in the past several years which have challenged this picture. I further discuss the reasons for the apparent close competition between pairing in s- and d-wave channels, particularly in those systems where one type of Fermi surface pocket - hole or electron - is missing. Observation of a transition between s- and d-wave symmetry, possibly via a time reversal symmetry breaking ;s + id; state, would provide an important confirmation of these ideas. Several proposals for detecting these novel phases are discussed, including the appearance of order parameter collective modes in Raman and optical conductivities. Transitions between two different types of s-wave states, involving various combinations of signs on Fermi surface pockets, can also proceed through a T-breaking ;s + is; state. I discuss recent work that suggests pairing may take place away from the Fermi level over a surprisingly large energy range, as well as the effect of glide plane symmetry of the Fe-based systems on the superconductivity, including various exotic, time and translational invariance breaking pair states that have been proposed. Finally, I address disorder issues, and the various ways systematic introduction of disorder can (and cannot) be used to extract information on gap symmetry and structure.

  6. Gauge Invariance and Symmetry Breaking by Topology and Energy Gap

    Directory of Open Access Journals (Sweden)

    Franco Strocchi

    2015-10-01

    Full Text Available For the description of observables and states of a quantum system, it may be convenient to use a canonical Weyl algebra of which only a subalgebra A, with a non-trivial center Z, describes observables, the other Weyl operators playing the role of intertwiners between inequivalent representations of A. In particular, this gives rise to a gauge symmetry described by the action of Z. A distinguished case is when the center of the observables arises from the fundamental group of the manifold of the positions of the quantum system. Symmetries that do not commute with the topological invariants represented by elements of Z are then spontaneously broken in each irreducible representation of the observable algebra, compatibly with an energy gap; such a breaking exhibits a mechanism radically different from Goldstone and Higgs mechanisms. This is clearly displayed by the quantum particle on a circle, the Bloch electron and the two body problem.

  7. Superconducting Gap Symmetry of LaFeP(O,F Observed by Impurity Doping Effect

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    Shigeki Miyasaka

    2016-08-01

    Full Text Available We have investigated Mn, Co and Ni substitution effects on polycrystalline samples of LaFePO0.95F0.05 by resistivity and magnetoresistance measurements. In LaFe1-xMxPO0.95F0.05 (M = Mn, Co and Ni, the superconducting transition temperature (Tc monotonously decreases with increasing the impurity doping level of x. There is a clear difference of Tc suppression rates among Mn, Co and Ni doping cases, and the decreasing rate of Tc by Mn doping as a magnetic impurity is larger than those by the nonmagnetic doping impurities (Co/Ni. This result indicates that in LaFePO0.95F0.05, Tc is rapidly suppressed by the pair-breaking effect of magnetic impurities, and the pairing symmetry is a full-gapped s-wave. In the nonmagnetic impurity-doped systems, the residual resistivity in the normal state has nearly the same value when Tc becomes zero. The residual resistivity value is almost consistent with the universal value of sheet resistance for two-dimensional superconductors, suggesting that Tc is suppressed by electron localization in Co/Ni-doped LaFePO0.95F0.05.

  8. Bulk evidence for single-Gap s-wave superconductivity in the intercalated graphite superconductor C6Yb.

    Science.gov (United States)

    Sutherland, Mike; Doiron-Leyraud, Nicolas; Taillefer, Louis; Weller, Thomas; Ellerby, Mark; Saxena, S S

    2007-02-09

    We report measurements of the in-plane electrical resistivity rho and thermal conductivity kappa of the intercalated graphite superconductor C6Yb down to temperatures as low as Tc/100. When a field is applied along the c axis, the residual electronic linear term kappa0/T evolves in an exponential manner for Hc1s-wave order parameter, and is a strong argument against the possible existence of multigap superconductivity.

  9. Classification of symmetry fractionalization in gapped $\\mathbb Z_2$ spin liquids

    OpenAIRE

    Qi, Yang; Cheng, Meng

    2016-01-01

    In quantum spin liquids, fractional spinon excitations carry half-integer spins and other fractional quantum numbers of lattice and time-reversal symmetries. Different patterns of symmetry fractionalization distinguish different spin liquid phases. In this work, we derive a general constraint on the symmetry fractionalization of spinons in a gapped spin liquid, realized in a system with an odd number of spin-$1/2$ per unit cell. In particular, when applied to kagome/triangular lattices, we ob...

  10. Angle-resolved photoemission studies of the superconducting gap symmetry in Fe-based superconductors

    Directory of Open Access Journals (Sweden)

    Y.-B. Huang

    2012-12-01

    Full Text Available The superconducting gap is the fundamental parameter that characterizes the superconducting state, and its symmetry is a direct consequence of the mechanism responsible for Cooper pairing. Here we discuss about angle-resolved photoemission spectroscopy measurements of the superconducting gap in the Fe-based high-temperature superconductors. We show that the superconducting gap is Fermi surface dependent and nodeless with small anisotropy, or more precisely, a function of the momentum location in the Brillouin zone. We show that while this observation seems inconsistent with weak coupling approaches for superconductivity in these materials, it is well supported by strong coupling models and global superconducting gaps. We also suggest that a smaller lifetime of the superconducting Cooper pairs induced by the momentum dependent interband scattering inherent to these materials could affect the residual density of states at low energies, which is critical for a proper evaluation of the superconducting gap.

  11. Emergence of topological semimetals in gap closing in semiconductors without inversion symmetry.

    Science.gov (United States)

    Murakami, Shuichi; Hirayama, Motoaki; Okugawa, Ryo; Miyake, Takashi

    2017-05-01

    A band gap for electronic states in crystals governs various properties of solids, such as transport, optical, and magnetic properties. Its estimation and control have been an important issue in solid-state physics. The band gap can be controlled externally by various parameters, such as pressure, atomic compositions, and external field. Sometimes, the gap even collapses by tuning some parameter. In the field of topological insulators, this closing of the gap at a time-reversal invariant momentum indicates a band inversion, that is, it leads to a topological phase transition from a normal insulator to a topological insulator. We show, through an exhaustive study on possible space groups, that the gap closing in inversion-asymmetric crystals is universal, in the sense that the gap closing always leads either to a Weyl semimetal or to a nodal-line semimetal. We consider three-dimensional spinful systems with time-reversal symmetry. The space group of the system and the wave vector at the gap closing uniquely determine which possibility occurs and where the gap-closing points or lines lie in the wave vector space after the closing of the gap. In particular, we show that an insulator-to-insulator transition never happens, which is in sharp contrast to inversion-symmetric systems.

  12. Sensitivity of gap symmetry to an incipient band: Application to iron based superconductors

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    Mishra, Vivek; Scalapino, Douglas; Maier, Thomas

    Observation of high temperature superconductivity in iron-based superconductors with a submerged hole band has attracted wide interest. A spin fluctuation mediated pairing mechanism has been proposed as a possible explanation for the high transition temperatures observed in these systems. Here we discuss the importance of the submerged band in the context of the gap symmetry. We show that the incipient band can lead to an attractive pairing interaction and thus have significant effects on the pairing symmetry. We propose a framework to include the effect of the incipient band in the standard multi-orbital spin-fluctuation theories which are widely used for studying various iron-based superconductors. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

  13. S wave propagation in acoustic anisotropic media

    Science.gov (United States)

    Stovas, Alexey

    2017-04-01

    The acoustic anisotropic medium can be defined in two ways. The first one is known as a pseudo-acoustic approximation (Alkhalifah, 1998) that is based on the fact that in TI media, P wave propagation is weakly dependent on parameter known as "vertical S-wave velocity" (Thomsen, 1986). The standard way to define the pseudo-acoustic approximation is to set this parameter to zero. However, as it was shown later (Grechka et al., 2004), there is "S wave artifact" in such a medium. Another way is to define the stack of horizontal solid-fluid layers and perform an upscaling based on the Backus (1962) averaging. The stiffness coefficient that responds to "vertical S wave velocity" turns to zero if any of layers has zero vertical S wave velocity. In this abstract, I analyze the S wave propagation is acoustic anisotropic medium and define important kinematic properties such as the group velocity surface and Dix-type equations. The kinematic properties can easily be defined from the slowness surface. In elastic transversely isotropic medium, the equations for P and SV wave slowness surfaces are coupled. Setting "vertical S wave velocity" to zero, results in decoupling of equations. I show that the S wave group velocity surface is given by quasi-astroidal form with the reference astroid defined by vertical and horizontal projections of group velocity. I show that there are cusps attached to both vertical and horizontal symmetry axes. The new S wave parameters include vertical, horizontal and normal moveout velocities. With the help of new parameterization, suitable for S wave, I also derived the Dix-type of equations to define the effective kinematical properties of S waves in multi-layered acoustic anisotropic medium. I have shown that effective media defined from P and S waves have different parameters. I also show that there are certain symmetries between P and S waves parameters and equations. The proposed method can be used for analysis of S waves in acoustic anisotropic

  14. Breaking inversion symmetry in a state-dependent honeycomb lattice: artificial graphene with tunable band gap

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    Weinberg, M.; Staarmann, C.; Ölschläger, C.; Simonet, J.; Sengstock, K.

    2016-06-01

    Here, we present the application of a novel method for controlling the geometry of a state-dependent honeycomb lattice: the energy offset between the two sublattices of the honeycomb structure can be adjusted by rotating the atomic quantization axis. This enables us to continuously tune between a homogeneous graphene-like honeycomb lattice and a triangular lattice and to open an energy gap at the characteristic Dirac points. We probe the symmetry of the lattice with microwave spectroscopy techniques and investigate the behavior of atoms excited to the second energy band. We find a striking influence of the energy gap at the Dirac cones onto the lifetimes of bosonic atoms in the excited band.

  15. Gap Balancing Sacrifices Joint-Line Maintenance to Improve Gap Symmetry: 5-Year Follow-Up of a Randomized Controlled Trial.

    Science.gov (United States)

    Babazadeh, Sina; Dowsey, Michelle M; Vasimalla, Michael G; Stoney, James D; Choong, Peter F M

    2017-08-24

    Gap balancing (GB) has been noted to sacrifice joint-line maintenance to improve gap symmetry. This study aims to determine whether this change affects function or quality of life in the midterm. A prospective blinded randomized controlled trial was completed with 103 patients randomized to measured resection (n = 52) or GB (n = 51). Primary outcome measured was femoral component rotation. Secondary outcomes measured were joint-line change, gap symmetry, and function and quality-of-life outcomes. At 5 years, 83 of 103 patients (85%) were assessed. There was no significant difference between groups in terms of functional or quality of life outcomes. A subgroup analysis revealed that there was no significant association between those with asymmetrical flexion and/or extension or medial and/or lateral gaps during knee replacement and subsequent functional outcomes. No significant difference was detected with those with an elevated joint line and postoperative function. In the midterm, the resultant change in joint-line and maintained gap symmetry noted with GB does not result in significant change to function or quality of life. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Symmetry analysis of odd- and even-frequency superconducting gap symmetries for time-reversal symmetric interactions

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    Geilhufe, R. Matthias; Balatsky, Alexander V.

    2018-01-01

    Odd-frequency superconductivity describes a class of superconducting states where the superconducting gap is an odd function in relative time and Matsubara frequency. We present a group theoretical analysis based on the linearized gap equation in terms of Shubnikov groups of the second kind. By discussing systems with spin-orbit coupling and an interaction kernel which is symmetric under the reversal of relative time, we show that both even- and odd-frequency gaps are allowed to occur. Specific examples are discussed for the square lattice, the octahedral lattice, and the tetragonal lattice. For irreducible representations that are even under the reversal of relative time the common combinations of s - and d -wave spin singlet and p -wave spin triplet gaps are revealed, irreducible representations that are odd under reversal of relative time give rise to s - and d -wave spin triplet and p -wave spin singlet gaps. Furthermore, we discuss the construction of a generalized Ginzburg-Landau theory in terms of the associated irreducible representations. The result complements the established classification of superconducting states of matter.

  17. Opening a band gap without breaking lattice symmetry: a new route toward robust graphene-based nanoelectronics.

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    Kou, Liangzhi; Hu, Feiming; Yan, Binghai; Frauenheim, Thomas; Chen, Changfeng

    2014-07-07

    Developing graphene-based nanoelectronics hinges on opening a band gap in the electronic structure of graphene, which is commonly achieved by breaking the inversion symmetry of the graphene lattice via an electric field (gate bias) or asymmetric doping of graphene layers. Here we introduce a new design strategy that places a bilayer graphene sheet sandwiched between two cladding layers of materials that possess strong spin-orbit coupling (e.g., Bi2Te3). Our ab initio and tight-binding calculations show that a proximity enhanced spin-orbit coupling effect opens a large (44 meV) band gap in bilayer graphene without breaking its lattice symmetry, and the band gap can be effectively tuned by an interlayer stacking pattern and significantly enhanced by interlayer compression. The feasibility of this quantum-well structure is demonstrated by recent experimental realization of high-quality heterojunctions between graphene and Bi2Te3, and this design also conforms to existing fabrication techniques in the semiconductor industry. The proposed quantum-well structure is expected to be especially robust since it does not require an external power supply to open and maintain a band gap, and the cladding layers provide protection against environmental degradation of the graphene layer in its device applications.

  18. Bott periodicity for the topological classification of gapped states of matter with reflection symmetry

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    Trifunovic, Luka; Brouwer, Piet

    2017-11-01

    Using a dimensional reduction scheme based on scattering theory, we show that the classification tables for topological insulators and superconductors with reflection symmetry can be organized in two period-2 and four period-8 cycles, similar to the Bott periodicity found for topological insulators and superconductors without spatial symmetries. With the help of the dimensional reduction scheme, the classification in arbitrary dimensions d ≥1 can be obtained from the classification in one dimension, for which we present a derivation based on relative homotopy groups and exact sequences to classify one-dimensional insulators and superconductors with reflection symmetry. The resulting classification is fully consistent with a comprehensive classification obtained recently by Shiozaki and Sato [Phys. Rev. B 90, 165114 (2014), 10.1103/PhysRevB.90.165114]. The use of a scattering-matrix-inspired method allows us to address the second descendant Z2 phase, for which the topological nontrivial phase was previously reported to be vulnerable to perturbations that break translation symmetry.

  19. Wigner functions of s waves

    DEFF Research Database (Denmark)

    Dahl, Jens Peder; Varro, S.; Wolf, A.

    2007-01-01

    We derive explicit expressions for the Wigner function of wave functions in D dimensions which depend on the hyperradius-that is, of s waves. They are based either on the position or the momentum representation of the s wave. The corresponding Wigner function depends on three variables......: the absolute value of the D-dimensional position and momentum vectors and the angle between them. We illustrate these expressions by calculating and discussing the Wigner functions of an elementary s wave and the energy eigenfunction of a free particle....

  20. Experimental Observation of Non-'S-Wave' Superconducting Behavior in Bulk Superconducting Tunneling Junctions of Yba2Cu3O7-δ

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    Leandro Jose Guerra

    1998-06-01

    Full Text Available Evidence of non-s-wave superconductivity from normal tunneling experiments in bulk tunneling junctions of YBa2Cu3O7-δ is presented. The I-V and dI/dV characteristics of bulk superconducting tunneling junctions of YBa2Cu3O7-δ have been measured at 77.0K and clear deviation from s-wave superconducting behavior has been observed. The result agrees with d-wave symmetry, and interpreting the data in this way, the magnitude of the superconducting energy gap, 2Δ, is found to be (0.038 ± 0.002 eV. Comparing this energy gap with Tc (2Δ/kB Tc = 5.735, indicates that these high-Tc superconductors are strongly correlated materials, which in contrast with BCS-superconductors are believed to be weakly correlated.

  1. Observability of surface Andreev bound states in a topological insulator in proximity to an s-wave superconductor

    NARCIS (Netherlands)

    Snelder, M.; Asano, Y.; Golubov, Alexandre Avraamovitch; Brinkman, Alexander

    2015-01-01

    To guide experimental work on the search for Majorana zero-energy modes, we calculate the superconducting pairing symmetry of a three-dimensional topological insulator in combination with an s-wave superconductor. We show how the pairing symmetry changes across different topological regimes. We

  2. Theoretical and experimental evidence for a nodal energy gap in MgB2

    Science.gov (United States)

    Agassi, Y. Dan; Oates, Daniel E.

    2017-11-01

    We present a phenomenological model that strongly suggests that the smaller of the two energy gaps in MgB2, the so-called π gap, contains nodal lines with a six-fold symmetry (i-wave). The model also indicates that the larger gap, the so-called σ gap, is conventional s-wave. The model is an extension of the BCS gap equation that accounts for the elastic anisotropy in MgB2 and the Coulomb repulsion. It is based on a phononic pairing mechanism and assumes no coupling between the two energy gaps in MgB2 at zero temperature. All of the parameters of the model, such as sound velocities and masses, are independently determined material constants. The results agree with a previous ad-hoc hypothesis that the π energy gap has six nodal lines. That hypothesis was motivated by low-temperature measurements of the surface impedance and intermodulation distortion in high-quality thin films. We briefly review experimental evidence in the literature that is relevant to the energy-gap symmetry. We find that the evidence from the literature for s-wave is inconclusive. Our finding is that the π gap has six nodal lines.

  3. Nodeless superconductivity and time-reversal symmetry breaking in the noncentrosymmetric superconductor Re24Ti5

    Science.gov (United States)

    Shang, T.; Pang, G. M.; Baines, C.; Jiang, W. B.; Xie, W.; Wang, A.; Medarde, M.; Pomjakushina, E.; Shi, M.; Mesot, J.; Yuan, H. Q.; Shiroka, T.

    2018-01-01

    The noncentrosymmetric superconductor Re24Ti5 , a time-reversal symmetry- (TRS-) breaking candidate with Tc=6 K , was studied by means of muon-spin rotation/relaxation (μ SR ) and tunnel-diode oscillator techniques. At the macroscopic level, its bulk superconductivity was investigated via electrical resistivity, magnetic susceptibility, and heat-capacity measurements. The low-temperature penetration depth, superfluid density, and electronic heat capacity all evidence an s -wave coupling with an enhanced superconducting gap. The spontaneous magnetic fields revealed by zero-field μ SR below Tc indicate a time-reversal symmetry breaking and thus the unconventional nature of superconductivity in Re24Ti5 . The concomitant occurrence of TRS breaking also in the isostructural Re6(Zr ,Hf ) compounds hints at its common origin in this superconducting family and that an enhanced spin-orbital coupling does not affect pairing symmetry.

  4. Extended s-wave superfluid of repulsively interacting three-component fermionic atoms in optical lattices

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    Suga, Sei-Ichiro; Inaba, Kensuke

    2014-03-01

    We investigate pairing symmetry of the superfluid state in repulsively interacting three-component (colors) fermionic atoms in optical lattices. This superfluid state appears, when two of the color-dependent three repulsions are much stronger than the other close to half filling. We evaluate the effective pairing interaction by collecting random-phase-approximation-type diagrams and ladder diagrams, and solve the Eliashberg equation within weak-coupling theory in square optical lattices. We find that pairing symmetry is an extended s-wave, although in the phase diagram the superfluid state is adjacent to the color-density wave or paired Mott insulator at half filling. The k-dependence of the superfluid order parameter is caused by quantum fluctuations of the staggered color-density wave. When the difference in the three repulsions is decreased, paring symmetry changes from an extended s-wave to a d-wave. We expect 6Li, 171Yb, 173Yb atoms and their mixtures in optical lattices to be possible candidates for observing this superfluid state. This work was supported by Grants-in-Aid for Scientific Research (C) (No. 23540467) and (B) (No. 25287104) from the Japan Society for the Promotion of Science.

  5. Mirror symmetry

    CERN Document Server

    Voisin, Claire

    1999-01-01

    This is the English translation of Professor Voisin's book reflecting the discovery of the mirror symmetry phenomenon. The first chapter is devoted to the geometry of Calabi-Yau manifolds, and the second describes, as motivation, the ideas from quantum field theory that led to the discovery of mirror symmetry. The other chapters deal with more specialized aspects of the subject: the work of Candelas, de la Ossa, Greene, and Parkes, based on the fact that under the mirror symmetry hypothesis, the variation of Hodge structure of a Calabi-Yau threefold determines the Gromov-Witten invariants of its mirror; Batyrev's construction, which exhibits the mirror symmetry phenomenon between hypersurfaces of toric Fano varieties, after a combinatorial classification of the latter; the mathematical construction of the Gromov-Witten potential, and the proof of its crucial property (that it satisfies the WDVV equation), which makes it possible to construct a flat connection underlying a variation of Hodge structure in the ...

  6. $S$-wave pairing symmetry in non-centrosymmetric superconductor Re$_3$W

    OpenAIRE

    Yan, Jing; Shan, Lei; Luo, Qiang; Wang, Weihua; Wen, Hai-Hu

    2008-01-01

    The alloys of non-centrosymmetric superconductor, Re$_3$W, which were reported to have an $\\alpha$-Mn structure [P. Greenfield and P. A. Beck, J. Metals, N. Y. \\textbf{8}, 265 (1959)] with $T_\\mathrm{c}=9 $K were prepared by arc melting. The ac susceptibility and low-temperature specific heat were measured on these alloys. It is found that there are two superconducting phases coexisting in the samples with $T_\\mathrm{c1}\\sim9 $K and $T_\\mathrm{c2}\\sim7 $K, both of which have a non-centrosymme...

  7. Inherited Symmetry

    Science.gov (United States)

    Attanucci, Frank J.; Losse, John

    2008-01-01

    In a first calculus course, it is not unusual for students to encounter the theorems which state: If f is an even (odd) differentiable function, then its derivative is odd (even). In our paper, we prove some theorems which show how the symmetry of a continuous function f with respect to (i) the vertical line: x = a or (ii) with respect to the…

  8. Dependence of s-waves on continuous dimension: The quantum oscillator and free systems

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, K.B. [Centro de Ciencias Fisicas, Universidad Nacional Autonoma de Mexico, Apartado Postal 48-3, Cuernavaca, Morelos 62251 (Mexico); Aceves-de-la-Cruz, F. [Departamento de Fisica, CUCEI, Universidad de Guadalajara, Av. Revolucion 1500, Guadalajara, Jalisco 44430 (Mexico)

    2006-12-15

    Wavefunctions with rotational symmetry (i.e., zero angular momentum) in D dimensions, are called s-waves. In quantum quadratic systems (free particle, harmonic and repulsive oscillators), their radial parts obey Schroedinger equations with a fictitious centrifugal (for integer D{>=}4) or centripetal (for D = 2) potential. These Hamiltonians close into the three-dimensional Lorentz algebra so(2,1), whose exceptional interval corresponds to the critical range of continuous dimensions 0s-waves in D>0 dimensions. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  9. Unconventional Superconductivity in La(7)Ir(3) Revealed by Muon Spin Relaxation: Introducing a New Family of Noncentrosymmetric Superconductor That Breaks Time-Reversal Symmetry.

    Science.gov (United States)

    Barker, J A T; Singh, D; Thamizhavel, A; Hillier, A D; Lees, M R; Balakrishnan, G; Paul, D McK; Singh, R P

    2015-12-31

    The superconductivity of the noncentrosymmetric compound La(7)Ir(3) is investigated using muon spin rotation and relaxation. Zero-field measurements reveal the presence of spontaneous static or quasistatic magnetic fields below the superconducting transition temperature T(c)=2.25  K-a clear indication that the superconducting state breaks time-reversal symmetry. Furthermore, transverse-field rotation measurements suggest that the superconducting gap is isotropic and that the pairing symmetry of the superconducting electrons is predominantly s wave with an enhanced binding strength. The results indicate that the superconductivity in La(7)Ir(3) may be unconventional and paves the way for further studies of this family of materials.

  10. Classification of spacetimes with symmetry

    Science.gov (United States)

    Hicks, Jesse W.

    Spacetimes with symmetry play a critical role in Einstein's Theory of General Relativity. Missing from the literature is a correct, usable, and computer accessible classification of such spacetimes. This dissertation fills this gap; specifically, we. i) give a new and different approach to the classification of spacetimes with symmetry using modern methods and tools such as the Schmidt method and computer algebra systems, resulting in ninety-two spacetimes; ii) create digital databases of the classification for easy access and use for researchers; iii) create software to classify any spacetime metric with symmetry against the new database; iv) compare results of our classification with those of Petrov and find that Petrov missed six cases and incorrectly normalized a significant number of metrics; v) classify spacetimes with symmetry in the book Exact Solutions to Einstein's Field Equations Second Edition by Stephani, Kramer, Macallum, Hoenselaers, and Herlt and in Komrakov's paper Einstein-Maxwell equation on four-dimensional homogeneous spaces using the new software.

  11. Pairing symmetries in cuprates: A Gorkov formalism

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Angsula, E-mail: angsula@ufam.edu.br [Departamento de Fisica, UFAM, Av. Rodrigo Octavio 3000, Japiim, 69077-000 Manaus, AM (Brazil); Pimentel, B.M. [Instituto de Fisica Teorica, Sao Paulo State University, P.O. Box 70532-2, 01156-970 Sao Paulo, SP (Brazil)

    2012-10-01

    Inspite of the direct evidence for Cooper pairing in the cuprates as in conventional superconductors, the pairing symmetry in the cuprate superconductors is still considered to be a controversial and a highly debatable topic. The microscopic equations appropriate for these new materials, essentially the yttrium based compounds, are discussed following Gorkov's formalism for the conventional superconductors. Various types of symmetry of the pairing parameter are considered. In this study we consider the anisotropic nature of the gap parameter to write the mean-field equations of the cuprates. We observe that the symmetry of the potential is fundamental in deciding the nature of the anisotropy in the gap parameter.

  12. 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.

  13. Off-shell effects in s-wave pion absorption

    Energy Technology Data Exchange (ETDEWEB)

    Hachenberg, F.; Pirnerdouble-dagger, H.J.

    1978-06-01

    The effect of s-wave pion absorption on the pion-nucleus optical potential is calculated. We assume absorption by two uncorrelated nucleons with off-shell pion rescattering. For the pion-nucleon interaction we develop a field theoretic model which can be used on- and off-mass shell. A fully relativistic calculation of the pion polarization operator then gives U/sup opt/ =-4..pi..B/sub orho//sup 2/(2..mu..)/sup -1/, with B/sub 0/= (0.094+i0.036) ..mu../sup -4/, as contribution from s-wave absorption to the optical potential. The imaginary part agrees well with the experimentally determined value, while pion dispersion (real part of B/sub o/) does not explain the observed repulsion of the s-wave pion nucleus interaction. We deomonstrate the relevance of oo-shell dynamics in pion-nucleus scattering. The ratio R/sub s/ of ..pi../sup -/-absorption rates by neutron-proton and proton-proton pairs is much smaller than predicted by on-shell models. For equal numbers of neutrons and protons we get R/sub s/approx. =3.0.We also apply the formalism to s-wave pion production in nucleon-nucleon collisions and obtain qualitative agreement with the data. In particular the longstanding puzzle of the small imaginary pion deuteron scattering length compared to Im B/sub 0/ is explained. Our claculation gives Im a/sub pid/=3.7 x 10/sup -3/..mu../sup -1/.

  14. Dynamical Shiba states from precessing magnetic moments in an s -wave superconductor

    Science.gov (United States)

    Kaladzhyan, Vardan; Hoffman, Silas; Trif, Mircea

    2017-05-01

    We study theoretically the dynamics of a Shiba state forming around precessing classical spin in an s -wave superconductor. Utilizing a rotating wave description for the precessing magnetic impurity, we find the resulting Shiba bound state quasienergy and the spatial extension of the Shiba wave function. We show that such a precession pertains to dc charge and spin currents flowing through a normal STM tip tunnel coupled to the superconductor in the vicinity of the impurity. We calculate these currents and find that they strongly depend on the magnetic impurity precession frequency, precession angle, and on the position of the Shiba energy level in the superconducting gap. The resulting charge current is found to be proportional to the difference between the electron and hole wave functions of the Shiba state, being a direct measure for such an asymmetry. By dynamically driving the impurity one can infer the spin dependence of the Shiba states in the absence of a spin-polarized STM tip.

  15. Two superconducting gaps in LaFeAsO0.92F0.08 revealed by A75s nuclear quadrupole resonance

    Science.gov (United States)

    Kawasaki, S.; Shimada, K.; Chen, G. F.; Luo, J. L.; Wang, N. L.; Zheng, Guo-Qing

    2008-12-01

    We report A75s nuclear quadrupole resonance studies on superconducting oxypnictide LaFeAsO0.92F0.08 (Tc=23K) . The temperature dependence of the spin-lattice relaxation rate (1/T1) decreases below Tc without a coherence (Hebel-Slichter) peak and shows a temperature dependence that is not simple power law nor exponential. We show that the result can be understood in terms of two superconducting gaps of either d - or ±s -wave symmetry, with the larger gap Δ1˜4kBTc and the smaller one Δ2˜1.5kBTc . Our result suggests that the multiple-gap feature is universal in the oxypnictide superconductors, which is probably associated with the multiple electronic band structures in this class of materials. We also find that 1/T1T above Tc increases with decreasing temperature, which suggests weak magnetic fluctuations in the normal state.

  16. Symmetry Breaking in Hofstadter's Butterfly in graphene

    Science.gov (United States)

    Forsythe, Carlos; Dean, Cory; Wang, Lei; Maher, Patrick; Ghahari, Fereshte; Moon, Pilkyung; Koshino, Mikito; Taniguchi, Takashi; Watanabe, Kenji; Shepard, Ken; Hone, Jim; Kim, Philip

    2013-03-01

    We will present magnetotransport measurements in hBN encapsulated bilayer graphene devices where one of hBN substrates provides a weak modulation of lattice potential. Under a strong magnetic field, interplay between periodic electric potential and quantizing magnetic field lead to a fractal energy spectrum known as Hofstadter's butterfly. In graphene, while spin and layer symmetry breakings are expected in dual gated devices under large magnetic fields, valley symmetry breaking in the Hofstadter regime is not so easily understood. We will present the observance of these measured gaps along with a discussion of symmetry breaking in our BLG-hBN devices. Further quantitative analysis of these breakings will be presented through the temperature dependence of quantized conductance at these gaps. Through careful modulation of temperature and electron density, we have extracted a range of activation energies associated with symmetry breakings. the speaker acknowledges support from the Columbia Optics and Quantum Electronics IGERT under NSF grant DGE-1069420

  17. Symmetry in chemistry

    CERN Document Server

    Jaffé, Hans H

    1977-01-01

    This book, devoted exclusively to symmetry in chemistry and developed in an essentially nonmathematical way, is a must for students and researchers. Topics include symmetry elements and operations, multiple symmetry operations, multiplication tables and point groups, group theory applications, and crystal symmetry. Extensive appendices provide useful tables.

  18. Symmetry enriched U(1) quantum spin liquids

    OpenAIRE

    Zou, Liujun; Wang, Chong; Senthil, T.

    2017-01-01

    We classify and characterize three dimensional $U(1)$ quantum spin liquids (deconfined $U(1)$ gauge theories) with global symmetries. These spin liquids have an emergent gapless photon and emergent electric/magnetic excitations (which we assume are gapped). We first discuss in great detail the case with time reversal and $SO(3)$ spin rotational symmetries. We find there are 15 distinct such quantum spin liquids based on the properties of bulk excitations. We show how to interpret them as gaug...

  19. CP symmetry in optical systems

    CERN Document Server

    Dana, Brenda; Malomed, Boris A

    2015-01-01

    We introduce a model of a dual-core optical waveguide with opposite signs of the group-velocity-dispersion (GVD) in the two cores, and a phase-velocity mismatch between them. The coupler is embedded into an active host medium, which provides for the linear coupling of a gain-loss type between the two cores. The same system can be derived, without phenomenological assumptions, by considering the three-wave propagation in a medium with the quadratic nonlinearity, provided that the depletion of the second-harmonic pump is negligible. This linear system offers an optical realization of the charge-parity ($\\mathcal{CP}$) symmetry, while the addition of the intra-core cubic nonlinearity breaks the symmetry. By means of direct simulations and analytical approximations, it is demonstrated that the linear system generates expanding Gaussian states, while the nonlinear one gives rise to broad oscillating solitons, as well as a general family of stable stationary gap solitons.

  20. Summary: symmetries and spin

    Energy Technology Data Exchange (ETDEWEB)

    Haxton, W.C. (Institute for Nuclear Theory, Department of Physcis, FM-15, University of Washington, Seattle, Washington 98195 (US))

    1989-05-01

    I discuss a number of the themes of the Symmetries and Spin session of the 8th International Symposium on High Energy Spin Physics: parity non-conservation, CP/T nonconservation, and tests of charge symmetry and charge independence.

  1. Wigner's Symmetry Representation Theorem

    Indian Academy of Sciences (India)

    IAS Admin

    This article elucidates the important role the no- tion of symmetry has played in physics. It dis- cusses the proof of one of the important theorems of quantum mechanics, viz., Wigner's Symmetry. Representation Theorem. It also shows how the representations of various continuous and dis- crete symmetries follow from the ...

  2. 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)

  3. Gapless Symmetry-Protected Topological Order

    Directory of Open Access Journals (Sweden)

    Thomas Scaffidi

    2017-11-01

    Full Text Available We introduce exactly solvable gapless quantum systems in d dimensions that support symmetry-protected topological (SPT edge modes. Our construction leads to long-range entangled, critical points or phases that can be interpreted as critical condensates of domain walls “decorated” with dimension (d-1 SPT systems. Using a combination of field theory and exact lattice results, we argue that such gapless SPT systems have symmetry-protected topological edge modes that can be either gapless or symmetry broken, leading to unusual surface critical properties. Despite the absence of a bulk gap, these edge modes are robust against arbitrary symmetry-preserving local perturbations near the edges. In two dimensions, we construct wave functions that can also be interpreted as unusual quantum critical points with diffusive scaling in the bulk but ballistic edge dynamics.

  4. W-symmetry

    CERN Document Server

    Bouwknegt, P G

    1995-01-01

    W-symmetry is an extension of conformal symmetry in two dimensions. Since its introduction in 1985, W-symmetry has become one of the central notions in the study of two-dimensional conformal field theory. The mathematical structures that underlie W-symmetry are so-called W-algebras, which are higher-spin extensions of the Virasoro algebra. This book contains a collection of papers on W-symmetry, covering the period from 1985 through 1993. Its main focus is the construction of W-algebras and their representation theory. A recurrent theme is the intimate connection between W-algebras and affine

  5. Empirical mode decomposition: a new tool for S-wave detection

    NARCIS (Netherlands)

    P.J. Oonincx

    2002-01-01

    textabstractSeismic signals consist of several typically short energy bursts, waves, exhibiting several patterns in terms of dominant frequency, amplitude and polarisation. Amongst others, a significant wave is the S-wave. To detect such S-waves one can use conventional techniques that are based on

  6. Seismic anisotropy inferred from direct S-wave-derived splitting measurements and its geodynamic implications beneath southeastern Tibetan Plateau

    Science.gov (United States)

    Kant Tiwari, Ashwani; Singh, Arun; Eken, Tuna; Singh, Chandrani

    2017-04-01

    The present study deals with detecting seismic anisotropy parameters beneath southeastern Tibet near Namcha Barwa Mountain using the splitting of direct S waves. We employ the reference station technique to remove the effects of source-side anisotropy. Seismic anisotropy parameters, splitting time delays, and fast polarization directions are estimated through analyses of a total of 501 splitting measurements obtained from direct S waves from 25 earthquakes ( ≥ 5.5 magnitude) that were recorded at 42 stations of the Namcha Barwa seismic network. We observe a large variation in time delays ranging from 0.64 to 1.68 s, but in most cases, it is more than 1 s, which suggests a highly anisotropic lithospheric mantle in the region. A comparison between direct S- and SKS-derived splitting parameters shows a close similarity, although some discrepancies exist where null or negligible anisotropy has been reported earlier using SKS. The seismic stations with hitherto null or negligible anisotropy are now supplemented with new measurements with clear anisotropic signatures. Our analyses indicate a sharp change in lateral variations of fast polarization directions (FPDs) from consistent SSW-ENE or W-E to NW-SE direction at the southeastern edge of Tibet. Comparison of the FPDs with Global Positioning System (GPS) measurements, absolute plate motion (APM) directions, and surface geological features indicates that the observed anisotropy and hence inferred deformation patterns are not only due to asthenospheric dynamics but are a combination of lithospheric deformation and sub-lithospheric (asthenospheric) mantle dynamics. Direct S-wave-based station-averaged splitting measurements with increased back-azimuths tend to fill the coverage gaps left in SKS measurements.

  7. From physical symmetries to emergent gauge symmetries

    Energy Technology Data Exchange (ETDEWEB)

    Barceló, Carlos [Instituto de Astrofísica de Andalucía (IAA-CSIC),Glorieta de la Astronomía, 18008 Granada (Spain); Carballo-Rubio, Raúl [Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Laboratory for Quantum Gravity & Strings,Department of Mathematics & Applied Mathematics, University of Cape Town,Private Bag, Rondebosch 7701 (South Africa); Di Filippo, Francesco [Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Dipartamento di Scienze Fisiche “E.R. Caianiello”, Università di Salerno,I-84081 Fisciano (Italy); Garay, Luis J. [Departamento de Física Teórica II, Universidad Complutense de Madrid, 28040 Madrid (Spain); Instituto de Estructura de la Materia (IEM-CSIC), Serrano 121, 28006 Madrid (Spain)

    2016-10-17

    Gauge symmetries indicate redundancies in the description of the relevant degrees of freedom of a given field theory and restrict the nature of observable quantities. One of the problems faced by emergent theories of relativistic fields is to understand how gauge symmetries can show up in systems that contain no trace of these symmetries at a more fundamental level. In this paper we start a systematic study aimed to establish a satisfactory mathematical and physical picture of this issue, dealing first with abelian field theories. We discuss how the trivialization, due to the decoupling and lack of excitation of some degrees of freedom, of the Noether currents associated with physical symmetries leads to emergent gauge symmetries in specific situations. An example of a relativistic field theory of a vector field is worked out in detail in order to make explicit how this mechanism works and to clarify the physics behind it. The interplay of these ideas with well-known results of importance to the emergent gravity program, such as the Weinberg-Witten theorem, are discussed.

  8. Protected Edge Modes without Symmetry

    Directory of Open Access Journals (Sweden)

    Michael Levin

    2013-05-01

    Full Text Available We discuss the question of when a gapped two-dimensional electron system without any symmetry has a protected gapless edge mode. While it is well known that systems with a nonzero thermal Hall conductance, K_{H}≠0, support such modes, here we show that robust modes can also occur when K_{H}=0—if the system has quasiparticles with fractional statistics. We show that some types of fractional statistics are compatible with a gapped edge, while others are fundamentally incompatible. More generally, we give a criterion for when an electron system with Abelian statistics and K_{H}=0 can support a gapped edge: We show that a gapped edge is possible if and only if there exists a subset of quasiparticle types M such that (1 all the quasiparticles in M have trivial mutual statistics, and (2 every quasiparticle that is not in M has nontrivial mutual statistics with at least one quasiparticle in M. We derive this criterion using three different approaches: a microscopic analysis of the edge, a general argument based on braiding statistics, and finally a conformal field theory approach that uses constraints from modular invariance. We also discuss the analogous result for two-dimensional boson systems.

  9. GAP Analysis Program (GAP)

    Data.gov (United States)

    Kansas Data Access and Support Center — The Kansas GAP Analysis Land Cover database depicts 43 land cover classes for the state of Kansas. The database was generated using a two-stage hybrid classification...

  10. Development of S-wave portable vibrator; S ha potable vibrator shingen no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Kaida, Y.; Matsubara, Y. [OYO Corp., Tokyo (Japan); Nijhof, V.; Brouwer, J.

    1996-05-01

    An S-wave portable vibrator to serve as a seismic source has been developed for the purpose of applying the shallow-layer reflection method to the study of the soil ground. The author, et al., who previously developed a P-wave portable vibrator has now developed an S-wave version, considering the advantage of the S-wave over the P-wave in that, for example, the S-wave velocity may be directly compared with the N-value representing ground strength and that the S-wave travels more slowly than the P-wave through sticky soil promising a higher-resolution exploration. The experimentally constructed S-wave vibrator consists of a conventional P-wave vibrator and an L-type wooden base plate combined therewith. Serving as the monitor for vibration is a conventional accelerometer without any modification. The applicability test was carried out at a location where a plank hammering test was once conducted for reflection aided exploration, and the result was compared with that of the plank hammering test. As the result, it was found that after some preliminary treatment the results of the two tests were roughly the same but that both reflected waves were a little sharper in the S-wave vibrator test than in the plank hammering test. 4 refs., 9 figs., 1 tab.

  11. Density functional theory calculations for the band gap and formation energy of Pr4-xCaxSi12O3+xN18-x; a highly disordered compound with low symmetry and a large cell size.

    Science.gov (United States)

    Hong, Sung Un; Singh, Satendra Pal; Pyo, Myoungho; Park, Woon Bae; Sohn, Kee-Sun

    2017-06-28

    A novel oxynitride compound, Pr4-xCaxSi12O3+xN18-x, synthesized using a solid-state route has been characterized as a monoclinic structure in the C2 space group using Rietveld refinement on synchrotron powder X-ray diffraction data. The crystal structure of this compound was disordered due to the random distribution of Ca/Pr and N/O ions at various Wyckoff sites. A pragmatic approach for an ab initio calculation based on density function theory (DFT) for this disordered compound has been implemented to calculate an acceptable value of the band gap and formation energy. In general, for the DFT calculation of a disordered compound, a sufficiently large super cell and infinite variety of ensemble configurations is adopted to simulate the random distribution of ions; however, such an approach is time consuming and cost ineffective. Even a single unit cell model gave rise to 43 008 independent configurations as an input model for the DFT calculations. Since it was nearly impossible to calculate the formation energy and the band gap energy for all 43 008 configurations, an elitist non-dominated sorting genetic algorithm (NSGA-II) was employed to find the plausible configurations. In the NSGA-II, all 43 008 configurations were mathematically treated as genomes and the calculated band gap and the formation energy as the objective (fitness) function. Generalized gradient approximation (GGA) was first employed in the preliminary screening using NSGA-II, and thereafter a hybrid functional calculation (HSE06) was executed only for the most plausible GGA-relaxed configurations with lower formation and higher band gap energies. The final band gap energy (3.62 eV) obtained after averaging over the selected configurations, resembles closely the experimental band gap value (4.11 eV).

  12. Symmetry Festival 2016

    CERN Document Server

    2016-01-01

    The Symmetry Festival is a science and art program series, the most important periodic event (see its history) to bring together scientists, artists, educators and practitioners interested in symmetry (its roots, what is behind, applications, etc.), or in the consequences of its absence.

  13. Symmetries in Optimal Control

    NARCIS (Netherlands)

    Schaft, A.J. van der

    1987-01-01

    It is argued that the existence of symmetries may simplify, as in classical mechanics, the solution of optimal control problems. A procedure for obtaining symmetries for the optimal Hamiltonian resulting from the Maximum Principle is given; this avoids the actual calculation of the optimal

  14. Charged fluids with symmetries

    Indian Academy of Sciences (India)

    Abstract. We investigate the role of symmetries for charged perfect fluids by assuming that spacetime admits a conformal Killing vector. The existence of a conformal symmetry places restrictions on the model. It is possible to find a general relationship for the Lie derivative of the electromagnetic field along the integral curves ...

  15. Symmetry and Interculturality

    Science.gov (United States)

    Marchis, Iuliana

    2009-01-01

    Symmetry is one of the fundamental concepts in Geometry. It is a Mathematical concept, which can be very well connected with Art and Ethnography. The aim of the article is to show how to link the geometrical concept symmetry with interculturality. For this mosaics from different countries are used.

  16. Symmetry groups of automata

    Science.gov (United States)

    Ugalde, Edgardo; Urías, Jesús

    1994-01-01

    Symmetry transformations on the input and output code spaces of deterministic finite automata (DFA) are introduced. We show that the symmetry groups of transformations are produced by group DFA (gDFA) whose set of states and set of inputs are subgroups of the symmetric groups S q and S k, respectively ( q is the number of states and k the number of input symbols). The set of transitions of a gDFA is also a group. The symmetries of the n-moment delay DFA, relevant for cellular automata, are studied in detail. In particular, we show that the n-moment delay DFA on two symbols are self-symmetric. The symmetry gDFA of the 2-moment delay DFA on two symbols is displayed in detail. An algorithm to construct the symmetry gDFA of arbitrary DFA is given. An application of gDFA to cellular automata dynamics is mentioned.

  17. Superconductivity in quantum wires: A symmetry analysis

    Science.gov (United States)

    Samokhin, K. V.

    2017-10-01

    We study properties of quantum wires with spin-orbit coupling and time reversal symmetry breaking, in normal and superconducting states. Electronic band structures are classified according to quasi-one-dimensional magnetic point groups, or magnetic classes. The latter belong to one of three distinct types, depending on the way the time reversal operation appears in the group elements. The superconducting gap functions are constructed using antiunitary operations and have different symmetry properties depending on the type of the magnetic point group. We obtain the spectrum of the Andreev boundary modes near the end of the wire in a model-independent way, using the semiclassical approach with the boundary conditions described by a phenomenological scattering matrix. Explicit expressions for the bulk topological invariants controlling the number of the boundary zero modes are presented in the general multiband case for two types of the magnetic point groups with real order parameters, corresponding to DIII and BDI symmetry classes.

  18. Symmetries and Boundary Conditions with a Twist

    Science.gov (United States)

    Zawadzki, Krissia; D'Amico, Irene; Oliveira, Luiz N.

    2017-10-01

    Interest in finite-size systems has risen in the last decades, due to the focus on nanotechnological applications and because they are convenient for numerical treatment that can subsequently be extrapolated to infinite lattices. Independently of the envisioned application, special attention must be given to boundary condition, which may or may not preserve the symmetry of the infinite lattice. Here, we present a detailed study of the compatibility between boundary conditions and conservation laws. The conflict between open boundary conditions and momentum conservation is well understood, but we examine other symmetries, as well: we discuss gauge invariance, inversion, spin, and particle-hole symmetry and their compatibility with open, periodic, and twisted boundary conditions. In the interest of clarity, we develop the reasoning in the framework of the one-dimensional half-filled Hubbard model, whose Hamiltonian displays a variety of symmetries. Our discussion includes analytical and numerical results. Our analytical survey shows that, as a rule, boundary conditions break one or more symmetries of the infinite-lattice Hamiltonian. The exception is twisted boundary condition with the special torsion Θ = πL/2, where L is the lattice size. Our numerical results for the ground-state energy at half-filling and the energy gap for L = 2-7 show how the breaking of symmetry affects the convergence to the L → ∞ limit. We compare the computed energies and gaps with the exact results for the infinite lattice drawn from the Bethe-Ansatz solution. The deviations are boundary-condition dependent. The special torsion yields more rapid convergence than open or periodic boundary conditions. For sizes as small as L = 7, the numerical results for twisted condition are very close to the L → ∞ limit. We also discuss the ground-state electronic density and magnetization at half filling under the three boundary conditions.

  19. An evaluation of numerical approaches for S-wave component simulation in rock blasting

    Directory of Open Access Journals (Sweden)

    Qidong Gao

    2017-10-01

    Full Text Available The shear wave (S-wave component of the total blast vibration always plays an important role in damage to rock or adjacent structures. Numerical approach has been considered as an economical and effective tool in predicting blast vibration. However, S-wave has not yet attracted enough attention in previous numerical simulations. In this paper, three typical numerical models, i.e. the continuum-based elastic model, the continuum-based damage model, and the coupled smooth particle hydrodynamics (SPH-finite element method (FEM model, were first introduced and developed to simulate the blasting of a single cylindrical charge. Then, the numerical results from different models were evaluated based on a review on the generation mechanisms of S-wave during blasting. Finally, some suggestions on the selection of numerical approaches for simulating generation of the blast-induced S-wave were put forward. Results indicate that different numerical models produce different results of S-wave. The coupled numerical model was the best, for its outstanding capacity in producing S-wave component. It is suggested that the model that can describe the cracking, sliding or heaving of rock mass, and the movement of fragments near the borehole should be selected preferentially, and priority should be given to the material constitutive law that could record the nonlinear mechanical behavior of rock mass near the borehole.

  20. Physics from symmetry

    CERN Document Server

    Schwichtenberg, Jakob

    2015-01-01

    This is a textbook that derives the fundamental theories of physics from symmetry.   It starts by introducing, in a completely self-contained way, all mathematical tools needed to use symmetry ideas in physics. Thereafter, these tools are put into action and by using symmetry constraints, the fundamental equations of Quantum Mechanics, Quantum Field Theory, Electromagnetism, and Classical Mechanics are derived. As a result, the reader is able to understand the basic assumptions behind, and the connections between the modern theories of physics. The book concludes with first applications of the previously derived equations.

  1. Gauge symmetry from decoupling

    Directory of Open Access Journals (Sweden)

    C. Wetterich

    2017-02-01

    Full Text Available Gauge symmetries emerge from a redundant description of the effective action for light degrees of freedom after the decoupling of heavy modes. This redundant description avoids the use of explicit constraints in configuration space. For non-linear constraints the gauge symmetries are non-linear. In a quantum field theory setting the gauge symmetries are local and can describe Yang–Mills theories or quantum gravity. We formulate gauge invariant fields that correspond to the non-linear light degrees of freedom. In the context of functional renormalization gauge symmetries can emerge if the flow generates or preserves large mass-like terms for the heavy degrees of freedom. They correspond to a particular form of gauge fixing terms in quantum field theories.

  2. Fundamental symmetries and interactions

    NARCIS (Netherlands)

    Jungmann, KP

    2005-01-01

    In nuclear physics numerous possibilities exist to investigate fundamental symmetries and interactions. In particular, the precise measurements of properties of fundamental fermions, searches for new interactions in beta-decays, and violations of discrete symmeties offer possibilities to search for

  3. Wigner's Symmetry Representation Theorem

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 19; Issue 10. Wigner's Symmetry Representation Theorem: At the Heart of Quantum Field Theory! Aritra Kr Mukhopadhyay. General Article Volume 19 Issue 10 October 2014 pp 900-916 ...

  4. Symmetry, beauty and evolution.

    Science.gov (United States)

    Enquist, M; Arak, A

    1994-11-10

    Humans and certain other species find symmetrical patterns more attractive than asymmetrical ones. These preferences may appear in response to biological signals, or in situations where there is no obvious signalling context, such as exploratory behaviour and human aesthetic response to pattern. It has been proposed that preferences for symmetry have evolved in animals because the degree of symmetry in signals indicates the signaller's quality. By contrast, we show here that symmetry preferences may arise as a by-product of the need to recognize objects irrespective of their position and orientation in the visual field. The existence of sensory biases for symmetry may have been exploited independently by natural selection acting on biological signals and by human artistic innovation. This may account for the observed convergence on symmetrical forms in nature and decorative art.

  5. Dihedral flavor symmetries

    Energy Technology Data Exchange (ETDEWEB)

    Blum, Alexander Simon

    2009-06-10

    This thesis deals with the possibility of describing the flavor sector of the Standard Model of Particle Physics (with neutrino masses), that is the fermion masses and mixing matrices, with a discrete, non-abelian flavor symmetry. In particular, mass independent textures are considered, where one or several of the mixing angles are determined by group theory alone and are independent of the fermion masses. To this end a systematic analysis of a large class of discrete symmetries, the dihedral groups, is analyzed. Mass independent textures originating from such symmetries are described and it is shown that such structures arise naturally from the minimization of scalar potentials, where the scalars are gauge singlet flavons transforming non-trivially only under the flavor group. Two models are constructed from this input, one describing leptons, based on the group D{sub 4}, the other describing quarks and employing the symmetry D{sub 14}. In the latter model it is the quark mixing matrix element V{sub ud} - basically the Cabibbo angle - which is at leading order predicted from group theory. Finally, discrete flavor groups are discussed as subgroups of a continuous gauge symmetry and it is shown that this implies that the original gauge symmetry is broken by fairly large representations. (orig.)

  6. Physics from symmetry

    CERN Document Server

    Schwichtenberg, Jakob

    2018-01-01

    This is a textbook that derives the fundamental theories of physics from symmetry. It starts by introducing, in a completely self-contained way, all mathematical tools needed to use symmetry ideas in physics. Thereafter, these tools are put into action and by using symmetry constraints, the fundamental equations of Quantum Mechanics, Quantum Field Theory, Electromagnetism, and Classical Mechanics are derived. As a result, the reader is able to understand the basic assumptions behind, and the connections between the modern theories of physics. The book concludes with first applications of the previously derived equations. Thanks to the input of readers from around the world, this second edition has been purged of typographical errors and also contains several revised sections with improved explanations. .

  7. Rigidity and symmetry

    CERN Document Server

    Weiss, Asia; Whiteley, Walter

    2014-01-01

    This book contains recent contributions to the fields of rigidity and symmetry with two primary focuses: to present the mathematically rigorous treatment of rigidity of structures, and to explore the interaction of geometry, algebra, and combinatorics. Overall, the book shows how researchers from diverse backgrounds explore connections among the various discrete structures with symmetry as the unifying theme.  Contributions present recent trends and advances in discrete geometry, particularly in the theory of polytopes. The rapid development of abstract polytope theory has resulted in a rich theory featuring an attractive interplay of methods and tools from discrete geometry, group theory, classical geometry, hyperbolic geometry and topology.  The volume will also be a valuable source as an introduction to the ideas of both combinatorial and geometric rigidity theory and its applications, incorporating the surprising impact of symmetry. It will appeal to students at both the advanced undergraduate and gradu...

  8. Symmetry, structure, and spacetime

    CERN Document Server

    Rickles, Dean

    2007-01-01

    In this book Rickles considers several interpretative difficulties raised by gauge-type symmetries (those that correspond to no change in physical state). The ubiquity of such symmetries in modern physics renders them an urgent topic in philosophy of physics. Rickles focuses on spacetime physics, and in particular classical and quantum general relativity. Here the problems posed are at their most pathological, involving the apparent disappearance of spacetime! Rickles argues that both traditional ontological positions should be replaced by a structuralist account according to which relational

  9. Measures with symmetry properties

    CERN Document Server

    Schindler, Werner

    2003-01-01

    Symmetries and invariance principles play an important role in various branches of mathematics. This book deals with measures having weak symmetry properties. Even mild conditions ensure that all invariant Borel measures on a second countable locally compact space can be expressed as images of specific product measures under a fixed mapping. The results derived in this book are interesting for their own and, moreover, a number of carefully investigated examples underline and illustrate their usefulness and applicability for integration problems, stochastic simulations and statistical applications.

  10. New onset S wave in pulmonary embolism: revisited (something old and something new)

    Science.gov (United States)

    Gupta, Prabha Nini; Pillai, Siju B; Ahmad, Sajan Z; Babu, Shifas M

    2013-01-01

    We report a case of a young man who had a new onset S wave in lead 1 in his ECG with typical symptoms of acute onset of dyspoena 2 months after an episode of deep vein thrombosis, S wave disappeared 6 days after thrombolysis. We report this case as the clinical course was very typical plus we have reviewed the literature regarding diagnosis and risk stratification of pulmonary embolism for the student, or the casualty medical officer. PMID:24275333

  11. Is isospin symmetry violated in the pion-nucleon sector at threshold?

    Energy Technology Data Exchange (ETDEWEB)

    Aschenauer, E.C. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Badertscher, A. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik; Bogdan, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik; Chatellard, D. [Neuchatel Univ. (Switzerland). Inst. de Physique; Egger, J.P. [Neuchatel Univ. (Switzerland). Inst. de Physique; Gabathuler, K. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Goudsmit, P.F.A. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik; Jeannet, E. [Neuchatel Univ. (Switzerland). Inst. de Physique; Leisi, H.J. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik; Matsinos, E. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik; Rusi El Hassani, A.J. [Universite Mohammed 5, Rabat (Morocco). Ecole Mohammadia d`Ingenieurs; Schroeder, H.C. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik; Sigg, D. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik; Simons, L.M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Zhao, Z.G. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. fuer Teilchenphysik

    1995-12-31

    The recently performed crystal-spectrometer X-ray experiments allow (for the first time) to address the problem of isospin-symmetry violation in the {pi} - N sector at at threshold directly, i.e. without extrapolation to threshold from data obtained at higher energies where s- and p-wave interactions are mixed. The way to detect violation of the isospin symmetry in general would be as follows. One assumes isospin symmetry to hold, and then determines constraints to the two s-wave scattering lengths (e.g. b{sub 0} = 1/3(a{sub 1} + 2a{sub 3}) and b{sub 1} = 1/3(a{sub 3} - a{sub 1})) from independent measurements in at least three different reactons. Inconsistencies among different constraints should indicate violation of the isospin symmetry. (orig.)

  12. Horror Vacui Symmetry.

    Science.gov (United States)

    Crumpecker, Cheryl

    2003-01-01

    Describes an art lesson used with children in the third grade to help them learn about symmetry, as well as encouraging them to draw larger than usual. Explains that students learn about the belief called "Horror Vacui" of the Northwest American Indian tribes and create their interpretation of this belief. (CMK)

  13. Exploring Metric Symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Zwart, P.H.; Grosse-Kunstleve, R.W.; Adams, P.D.

    2006-07-31

    Relatively minor perturbations to a crystal structure can in some cases result in apparently large changes in symmetry. Changes in space group or even lattice can be induced by heavy metal or halide soaking (Dauter et al, 2001), flash freezing (Skrzypczak-Jankun et al, 1996), and Se-Met substitution (Poulsen et al, 2001). Relations between various space groups and lattices can provide insight in the underlying structural causes for the symmetry or lattice transformations. Furthermore, these relations can be useful in understanding twinning and how to efficiently solve two different but related crystal structures. Although (pseudo) symmetric properties of a certain combination of unit cell parameters and a space group are immediately obvious (such as a pseudo four-fold axis if a is approximately equal to b in an orthorhombic space group), other relations (e.g. Lehtio, et al, 2005) that are less obvious might be crucial to the understanding and detection of certain idiosyncrasies of experimental data. We have developed a set of tools that allows straightforward exploration of possible metric symmetry relations given unit cell parameters and a space group. The new iotbx.explore{_}metric{_}symmetry command produces an overview of the various relations between several possible point groups for a given lattice. Methods for finding relations between a pair of unit cells are also available. The tools described in this newsletter are part of the CCTBX libraries, which are included in the latest (versions July 2006 and up) PHENIX and CCI Apps distributions.

  14. Introduction to chiral symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Koch, V.

    1996-01-08

    These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. Effective chiral models such as the linear and nonlinear sigma model will be discussed as well as the essential ideas of chiral perturbation theory. Some applications to the physics of ultrarelativistic heavy ion collisions will be presented.

  15. Introduction to Chiral Symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Koch, Volker [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2017-05-09

    These lectures are an attempt to a pedagogical introduction into the elementary concepts of chiral symmetry in nuclear physics. We will also discuss some effective chiral models such as the linear and nonlinear sigma model as well as the essential ideas of chiral perturbation theory. We will present some applications to the physics of ultrarelativistic heavy ion collisionsd.

  16. Symmetries in fundamental physics

    CERN Document Server

    Sundermeyer, Kurt

    2014-01-01

    Over the course of the last century it has become clear that both elementary particle physics and relativity theories are based on the notion of symmetries. These symmetries become manifest in that the "laws of nature" are invariant under spacetime transformations and/or gauge transformations. The consequences of these symmetries were analyzed as early as in 1918 by Emmy Noether on the level of action functionals. Her work did not receive due recognition for nearly half a century, but can today be understood as a recurring theme in classical mechanics, electrodynamics and special relativity, Yang-Mills type quantum field theories, and in general relativity. As a matter of fact, as shown in this monograph, many aspects of physics can be derived solely from symmetry considerations. This substantiates the statement of E.P. Wigner "... if we knew all the laws of nature, or the ultimate Law of nature, the invariance properties of these laws would not furnish us new information." Thanks to Wigner we now also unders...

  17. Symmetries in fundamental physics

    CERN Document Server

    Sundermeyer, Kurt

    2014-01-01

    Over the course of the last century it has become clear that both elementary particle physics and relativity theories are based on the notion of symmetries. These symmetries become manifest in that the "laws of nature" are invariant under spacetime transformations and/or gauge transformations. The consequences of these symmetries were analyzed as early as in 1918 by Emmy Noether on the level of action functionals. Her work did not receive due recognition for nearly half a century, but can today be understood as a recurring theme in classical mechanics, electrodynamics and special relativity, Yang-Mills type quantum field theories, and in general relativity. As a matter of fact, as shown in this monograph, many aspects of physics can be derived solely from symmetry considerations. This substantiates the statement of E.P.Wigner "... if we knew all the laws of nature, or the ultimate Law of nature, the invariance properties of these laws would not furnish us new information." Thanks to Wigner we now also underst...

  18. Broken symmetry makes helium

    CERN Multimedia

    Gray, P L

    2003-01-01

    "The subatomic pion particle breaks the charge symmetry rule that governs both fusion and decay. In experiments performed at the Indiana University Cyclotron Laboratory, physicists forced heavy hydrogen (1 proton + 1 neutron) to fuse into helium in a controlled, measurable environment" (1 paragraph).

  19. Testing for central symmetry

    NARCIS (Netherlands)

    Einmahl, John; Gan, Zhuojiong

    Omnibus tests for central symmetry of a bivariate probability distribution are proposed. The test statistics compare empirical measures of opposite regions. Under rather weak conditions, we establish the asymptotic distribution of the test statistics under the null hypothesis; it follows that they

  20. In- and outbound spreading of a free-particle s-wave

    DEFF Research Database (Denmark)

    Bialynicki-Birula, i.; Cirone, M. A.; Dahl, Jens Peder

    2002-01-01

    We show that a free quantum particle in two dimensions with zero angular momentum (s wave) in the form of a ring-shaped wave packet feels an attraction towards the center of the ring, leading first to a contraction followed by an expansion. An experiment to demonstrate this effect is also outlined....

  1. Non-triviality matters: examining the interplay between s-wave superconductivity and topological surface states

    NARCIS (Netherlands)

    Snelder, M.

    2015-01-01

    The main focus of this thesis is to understand the correlations present at the s-wave/three-dimensional topological insulator interface both theoretically and experimentally. In the future, devices containing these kind of interfaces can be used to create and manipulate a Majorana zero-energy mode

  2. Chiral Symmetry, Heavy Quark Symmetry and Bound States

    OpenAIRE

    Yoshida, Yuhsuke

    1995-01-01

    I investigate the bound state problems of lowest-lying mesons and heavy mesons. Chiral symmetry is essential when one consider lowest-lying mesons. Heavy quark symmetry plays an central role in considering the semi-leptonic form factors of heavy mesons. Various properties based on the symmetries are revealed using Bethe-Salpeter equations.

  3. Odd-parity superconductivity in the vicinity of inversion symmetry breaking in spin-orbit-coupled systems

    Science.gov (United States)

    Kozii, Vladyslav; Fu, Liang; Massachusetts institute of technology Team

    We study superconductivity in spin-orbit-coupled systems in the vicinity of inversion symmetry breaking. We find that due to the presence of spin-orbit coupling, fluctuations of the incipient parity-breaking order generate an attractive pairing interaction in an odd-parity pairing channel, which competes with the s-wave pairing. We show that Coulomb repulsion or an external Zeeman field suppresses the s-wave pairing and promotes the odd-parity superconducting state. Our work provides a new mechanism for odd-parity pairing and opens a route to novel topological superconductivity. This work is supported by the David and Lucile Packard foundation.

  4. Natural selection of visual symmetries

    NARCIS (Netherlands)

    Helm, P.A. van der

    2002-01-01

    Implicitly, Wynn's target article starts from the transformational definition of symmetry. Unlike his suggestion, this traditional definition and the recent holographic definition are relevant to the discussion on the cognitive evolution of visual symmetries. These definitions reveal underlying

  5. On Symmetries in Optimal Control

    NARCIS (Netherlands)

    Schaft, A.J. van der

    1986-01-01

    We discuss the use of symmetries in solving optimal control problems. In particular a procedure for obtaining symmetries is given which can be performed before the actual calculation of the optimal control and optimal Hamiltonian.

  6. P and S wave responses of bacterial biopolymer formation in unconsolidated porous media

    Science.gov (United States)

    Noh, Dong-Hwa; Ajo-Franklin, Jonathan B.; Kwon, Tae-Hyuk; Muhunthan, Balasingam

    2016-04-01

    This study investigated the P and S wave responses and permeability reduction during bacterial biopolymer formation in unconsolidated porous media. Column experiments with fine sands, where the model bacteria Leuconostoc mesenteroides were stimulated to produce insoluble biopolymer, were conducted while monitoring changes in permeability and P and S wave responses. The bacterial biopolymer reduced the permeability by more than 1 order of magnitude, occupying ~10% pore volume after 38 days of growth. This substantial reduction was attributed to the bacterial biopolymer with complex internal structures accumulated at pore throats. S wave velocity (VS) increased by more than ~50% during biopolymer accumulation; this indicated that the bacterial biopolymer caused a certain level of stiffening effect on shear modulus of the unconsolidated sediment matrix at low confining stress conditions. Whereas replacing pore water by insoluble biopolymer was observed to cause minimal changes in P wave velocity (VP) due to the low elastic moduli of insoluble biopolymer. The spectral ratio analyses revealed that the biopolymer formation caused a ~50-80% increase in P wave attenuation (1/QP) at the both ultrasonic and subultrasonic frequency ranges, at hundreds of kHz and tens of kHz, respectively, and a ~50-60% increase in S wave attenuation (1/QS) in the frequency band of several kHz. Our results reveal that in situ biopolymer formation and the resulting permeability reduction can be effectively monitored by using P and S wave attenuation in the ultrasonic and subultrasonic frequency ranges. This suggests that field monitoring using seismic logging techniques, including time-lapse dipole sonic logging, may be possible.

  7. The Emergence of Dirac points in Photonic Crystals with Mirror Symmetry

    Science.gov (United States)

    He, Wen-Yu; Chan, C. T.

    2015-01-01

    We show that Dirac points can emerge in photonic crystals possessing mirror symmetry when band gap closes. The mechanism of generating Dirac points is discussed in a two-dimensional photonic square lattice, in which four Dirac points split out naturally after the touching of two bands with different parity. The emergence of such nodal points, characterized by vortex structure in momentum space, is attributed to the unavoidable band crossing protected by mirror symmetry. The Dirac nodes can be unbuckled through breaking the mirror symmetry and a photonic analog of Chern insulator can be achieved through time reversal symmetry breaking. Breaking time reversal symmetry can lead to unidirectional helical edge states and breaking mirror symmetry can reduce the band gap to amplify the finite size effect, providing ways to engineer helical edge states. PMID:25640993

  8. Broken symmetries in field theory

    NARCIS (Netherlands)

    Kok, Mark Okker de

    2008-01-01

    The thesis discusses the role of symmetries in Quantum Field Theory. Quantum Field Theory is the mathematical framework to describe the physics of elementary particles. A symmetry here means a transformation under which the model at hand is invariant. Three types of symmetry are distinguished: 1.

  9. Dynamical Symmetries in Classical Mechanics

    Science.gov (United States)

    Boozer, A. D.

    2012-01-01

    We show how symmetries of a classical dynamical system can be described in terms of operators that act on the state space for the system. We illustrate our results by considering a number of possible symmetries that a classical dynamical system might have, and for each symmetry we give examples of dynamical systems that do and do not possess that…

  10. Implicit Hamiltonian Systems with Symmetry

    NARCIS (Netherlands)

    Schaft, A.J. van der

    1998-01-01

    Implicit Hamiltonian systems with symmetry are treated by exploiting the notion of symmetry of Dirac structures. It is shown how Dirac structures can be reduced to Dirac structures on the orbit space of the symmetry group, leading to a reduced implicit (generalized) Hamiltonian system. The approach

  11. Implicit Hamiltonian systems with symmetry

    NARCIS (Netherlands)

    van der Schaft, Arjan

    1998-01-01

    Implicit Hamiltonian systems with symmetry are treated by exploiting the notion of symmetry of Dirac structures. It is shown how Dirac structures can be reduced to Dirac structures on the orbit space of the symmetry group, leading to a reduced implicit (generalized) Hamiltonian system. The approach

  12. Emergence of Symmetries from Entanglement

    CERN Multimedia

    CERN. Geneva

    2016-01-01

    Maximal Entanglement appears to be a key ingredient for the emergence of symmetries. We first illustrate this phenomenon using two examples: the emergence of conformal symmetry in condensed matter systems and  the relation of tensor networks to holography. We further present a Principle of Maximal Entanglement that seems to dictate to a large extend the structure of gauge symmetry.

  13. Asymmetry, Symmetry and Beauty

    Directory of Open Access Journals (Sweden)

    Abbe R. Kopra

    2010-07-01

    Full Text Available Asymmetry and symmetry coexist in natural and human processes.  The vital role of symmetry in art has been well demonstrated. This article highlights the complementary role of asymmetry. Further we show that the interaction of asymmetric action (recursion and symmetric opposition (sinusoidal waves are instrumental in generating creative features (relatively low entropy, temporal complexity, novelty (less recurrence in the data than in randomized copies and complex frequency composition. These features define Bios, a pattern found in musical compositions and in poetry, except for recurrence instead of novelty. Bios is a common pattern in many natural and human processes (quantum processes, the expansion of the universe, gravitational waves, cosmic microwave background radiation, DNA, physiological processes, animal and human populations, and economic time series. The reduction in entropy is significant, as it reveals creativity and contradicts the standard claim of unavoidable decay towards disorder. Artistic creations capture fundamental features of the world.

  14. Segmentation Using Symmetry Deviation

    DEFF Research Database (Denmark)

    Hollensen, Christian; Højgaard, L.; Specht, L.

    2011-01-01

    Purpose: The manual delineation of gross tumour volume(GTV) for radiation therapy for head and neck cancer patients relies in some degree of pathological deviation from normal anatomical symmetry. The purpose of this study is to introduce a novel method for 3-dimensional determination of GTV...... hypopharyngeal cancer patients to find anatomical symmetry and evaluate it against the standard deviation of the normal patients to locate pathologic volumes. Combining the information with an absolute PET threshold of 3 Standard uptake value (SUV) a volume was automatically delineated. The overlap of automated...... segmentations on manual contours was evaluated using concordance index and sensitivity for the hypopharyngeal patients. The resulting concordance index and sensitivity was compared with the result of using a threshold of 3 SUV using a paired t-test. Results: The anatomical and symmetrical atlas was constructed...

  15. Precursors and BRST symmetry

    Science.gov (United States)

    de Boer, Jan; Freivogel, Ben; Kabir, Laurens; Lokhande, Sagar F.

    2017-07-01

    In the AdS/CFT correspondence, bulk information appears to be encoded in the CFT in a redundant way. A local bulk field corresponds to many different non-local CFT operators (precursors). We recast this ambiguity in the language of BRST symmetry, and propose that in the large N limit, the difference between two precursors is a BRST exact and ghost-free term. This definition of precursor ambiguities has the advantage that it generalizes to any gauge theory. Using the BRST formalism and working in a simple model with global symmetries, we re-derive a precursor ambiguity appearing in earlier work. Finally, we show within this model that the obtained ambiguity has the right number of parameters to explain the freedom to localize precursors within different spatial regions of the boundary order by order in the large N expansion.

  16. Symmetry in music

    Energy Technology Data Exchange (ETDEWEB)

    Herrero, O F, E-mail: o.f.herrero@hotmail.co [Conservatorio Superior de Musica ' Eduardo Martinez Torner' Corrada del Obispo s/n 33003 - Oviedo - Asturias (Spain)

    2010-06-01

    Music and Physics are very close because of the symmetry that appears in music. A periodic wave is what music really is, and there is a field of Physics devoted to waves researching. The different musical scales are the base of all kind of music. This article tries to show how this musical scales are made, how the consonance is the base of many of them and how symmetric they are.

  17. Local Rotational Symmetries.

    Science.gov (United States)

    1985-08-01

    way to choose among them. Spirals can occur in natural figures, e.g. a spiralled tail or a coil of rope or vine tendril, and in line drawings. Since...generated and removes it and all regions similar to it from the list of regions. The end result is a pruned list of distinct optimal regions. 4.7...that, at least to a first approximation, the potential symmetry regions pruned by the locality restriction are not perceptually salient. For example

  18. Cluster Symmetries and Dynamics

    Directory of Open Access Journals (Sweden)

    Freer Martin

    2016-01-01

    Full Text Available Many light nuclei display behaviour that indicates that rather than behaving as an A-body systems, the protons and neutrons condense into clusters. The α-particle is the most obvious example of such clustering. This contribution examines the role of such α-clustering on the structure, symmetries and dynamics of the nuclei 8Be, 12C and 16O, recent experimental measurements and future perspectives.

  19. Symmetry and quantum mechanics

    CERN Document Server

    Corry, Scott

    2016-01-01

    This book offers an introduction to quantum mechanics for professionals, students, and others in the field of mathematics who have a minimal background in physics with an understanding of linear algebra and group theory. It covers such topics as Lie groups, algebras and their representations, and analysis (Hilbert space, distributions, the spectral Theorem, and the Stone-Von Neumann Theorem). The book emphasizes the role of symmetry and is useful to physicists as it provides a mathematical introduction to the topic.

  20. Nuclear magnetic resonance in low-symmetry superconductors

    Science.gov (United States)

    Cavanagh, D. C.; Powell, B. J.

    2018-01-01

    We consider the nuclear spin-lattice relaxation rate 1 /T1 in superconductors with accidental nodes, i.e., zeros of the order parameter that are not enforced by its symmetries. Such nodes in the superconducting gap are not constrained by symmetry to a particular position on the Fermi surface. We show, analytically and numerically, that a Hebel-Slichter-like peak occurs even in the absence of an isotropic component of the superconducting gap. For a gap with symmetry-required nodes the Fermi velocity at the node must point along the node. For accidental nodes this is not, in general, the case. This leads to additional terms in spectral function and hence the density of states. These terms lead to a logarithmic divergence in 1 /T1T at T →Tc- in models neglecting disorder and interactions [except for those leading to superconductivity; here T is temperature, Tc-=limδ→0(Tc-δ ) , and Tc is the critical temperature]. This contrasts with the usual Hebel-Slichter peak which arises from the coherence factors due to the isotropic component of the gap and leads to a divergence in 1 /T1T somewhat below Tc. The divergence in superconductors with accidental nodes is controlled by either disorder or additional electron-electron interactions. However, for reasonable parameters, neither of these effects removes the peak altogether. This provides a simple experimental method to distinguish between symmetry-required and accidental nodes.

  1. Symmetry of “Twins”

    Directory of Open Access Journals (Sweden)

    Vladan Nikolić

    2015-02-01

    Full Text Available The idea of construction of twin buildings is as old as architecture itself, and yet there is hardly any study emphasizing their specificity. Most frequently there are two objects or elements in an architectural composition of “twins” in which there may be various symmetry relations, mostly bilateral symmetries. The classification of “twins” symmetry in this paper is based on the existence of bilateral symmetry, in terms of the perception of an observer. The classification includes both, 2D and 3D perception analyses. We start analyzing a pair of twin buildings with projection of the architectural composition elements in 2D picture plane (plane of the composition and we distinguish four 2D keyframe cases based on the relation between the bilateral symmetry of the twin composition and the bilateral symmetry of each element. In 3D perception for each 2D keyframe case there are two sub-variants, with and without a symmetry plane parallel to the picture plane. The bilateral symmetry is dominant if the corresponding symmetry plane is orthogonal to the picture plane. The essence of the complete classification is relation between the bilateral (dominant symmetry of the architectural composition and the bilateral symmetry of each element of that composition.

  2. Study on P-wave and S-wave velocity in dry and wet sandstones of Tushka region, Egypt

    Directory of Open Access Journals (Sweden)

    Mohamed A. Kassab

    2015-03-01

    The derived equations can be used for the prediction of P-wave velocity of wet rock samples from the P-wave velocity of dry rock samples, and the S-wave velocity of wet rock samples can be predicted from the S-wave velocity of dry rock samples. A strong linear correlation between P-wave velocity and S-wave velocity of dry rock samples and between P-wave velocity and S-wave velocity of wet rock samples was found. The resulting linear equations can be used for the estimation of S-wave velocity from the P-wave velocity in the case of both dry and wet rock samples.

  3. Symmetries of nonlinear ordinary differential equations: The ...

    Indian Academy of Sciences (India)

    2015-10-21

    Oct 21, 2015 ... Lie symmetry analysis is one of the powerful tools to analyse nonlinear ordinary differential equations. We review the effectiveness of this method in terms of various symmetries. We present the method of deriving Lie point symmetries, contact symmetries, hidden symmetries, nonlocal symmetries, ...

  4. The gamma gamma --> pi + pi - S wave in the CELLO experiment

    Science.gov (United States)

    Kaloshin, A. E.; Persikov, V. M.

    1993-10-01

    We analyze the CELLO angular distributions $\\gamma\\gamma\\rightarrow\\pi^+\\pi^-$ with the unitary model \\cite{KS-86} for helicity 2 amplitude. In contrast to previous analysis \\cite{CELLO} we do not see any QED damping. The obtained S--wave does not contradict to low--energy theorem and demonstrates more clealy the resonance--like behaviour near 1.3 Gev.

  5. S WAVE IN PULMONARY EMBOLISM, A NEW ECG SIGN TO AID THROMBOLYSIS

    Directory of Open Access Journals (Sweden)

    Thomas John

    2012-11-01

    Full Text Available Acute pulmonary embolism is a devastating disease that often leads to mortality . Previous investigators have found that thrombolysis reduces mortality in men but not significantly in women with pulmonary embolism. Many of the previous studies are with tenecteplase and alteplase. Here, we describe intra - venous thrombolysis with streptokinase in seven patients with pulmonary embolism who survived including two women. Further, we have one patient who had a new onset of S wave in lead I which subsequently disappeared after embolectomy. We also comment on the usefulness of shock sign in 2 deciding on thrombolysis .We propose a new sign for noninvasive assessment of need for thrombolysis in pulmonary embolism. New onset S wave in Lead I in pulmonary embolism can be used as a new sign for deciding the need for thrombolysis. When added to the shock sign it can be used in the emergency deparment to decide the need for thrombolysis. Further, there are no clear end points as to when to stop thrombolysis. In all 4 patients we switched to heparin when spontaneous bleeding or oozing started. In all 4 patients subsequent CT scans showed that the patient has mild to moderate resolution of the pulmonary embolism and patients remained stable and have been discharged and are under regular follow up. Hence we propose that bleeding can be used as an end point for thrombolysis in acute pulmonary embolism. We also describe a patient who had new onset S wave that disappeared after successful pulmonary embolectomy. Probably, the S wave is a marker of main pulmonary artery branch occlusions.

  6. APPLICATION OF A HEURISTIC METHOD FOR THE ESTIMATION OF S-WAVE VELOCITY STRUCTURE

    Directory of Open Access Journals (Sweden)

    Alfaro Castillo Andrés José

    2006-08-01

    Full Text Available The assessment of local site effects is one of the most important subjects in Engineering Seismology. In order to perform an assessment, it is necessary to determine the S-wave velocity structure of the site. Additionally, in some basins, it is very important to know the deep sedimentary structure, due to the amplification phenomena of low frequency waves. There are several techniques to achieve this purpose; probably the most inexpensive technique is using the vertical component of microtremors measured with an array of seismographs. The phase velocity of Rayleigh waves is inverted to an S-wave velocity (Vs profile  using optimization techniques. Most of the time, least square methods have been applied in the inversion.Recently, heuristic methods have also been used for the estimation of the S-wave velocity structure from microtremor.In this study seven arrays of microtremors in the city of Tsukuba city were performed, located to the NE edge of Kanto Basin, in order to estimate the deep S-wave velocity structure. The spatial autocorrelationmethod SPAC was used to determine phase velocity dispersion curves in the frequency range from 0.3-2.5 Hz. The determination of Vs profiles reached a depth of 750 m. Two methods were used to estimate the Swavevelocity structure: Inversion method and a heuristic method via the combination of Downhill Simplex Algorithm with a Very Fast Simulated Annealing Method. Comparisons with Vs from the existent resultsfrom PS-logging tests at the center of the array showed the reliability of the heuristic method.

  7. S/WAVES: The Radio and Plasma Wave Investigation on the STEREO Mission

    Science.gov (United States)

    Bougeret, J. L.; Goetz, K.; Kaiser, M. L.; Bale, S. D.; Kellogg, P. J.; Maksimovic, M.; Monge, N.; Monson, S. J.; Astier, P. L.; Davy, S.; Dekkali, M.; Hinze, J. J.; Manning, R. E.; Aguilar-Rodriguez, E.; Bonnin, X.; Briand, C.; Cairns, I. H.; Cattell, C. A.; Cecconi, B.; Eastwood, J.; Ergun, R. E.; Fainberg, J.; Hoang, S.; Huttunen, K. E. J.; Krucker, S.; Lecacheux, A.; MacDowall, R. J.; Macher, W.; Mangeney, A.; Meetre, C. A.; Moussas, X.; Nguyen, Q. N.; Oswald, T. H.; Pulupa, M.; Reiner, M. J.; Robinson, P. A.; Rucker, H.; Salem, C.; Santolik, O.; Silvis, J. M.; Ullrich, R.; Zarka, P.; Zouganelis, I.

    2008-04-01

    This paper introduces and describes the radio and plasma wave investigation on the STEREO Mission: STEREO/WAVES or S/WAVES. The S/WAVES instrument includes a suite of state-of-the-art experiments that provide comprehensive measurements of the three components of the fluctuating electric field from a fraction of a hertz up to 16 MHz, plus a single frequency channel near 30 MHz. The instrument has a direction finding or goniopolarimetry capability to perform 3D localization and tracking of radio emissions associated with streams of energetic electrons and shock waves associated with Coronal Mass Ejections (CMEs). The scientific objectives include: (i) remote observation and measurement of radio waves excited by energetic particles throughout the 3D heliosphere that are associated with the CMEs and with solar flare phenomena, and (ii) in-situ measurement of the properties of CMEs and interplanetary shocks, such as their electron density and temperature and the associated plasma waves near 1 Astronomical Unit (AU). Two companion papers provide details on specific aspects of the S/WAVES instrument, namely the electric antenna system (Bale et al., Space Sci. Rev., 2007) and the direction finding technique (Cecconi et al., Space Sci. Rev., 2007).

  8. Propagation of S-waves Through the Sediments in the Mississippi Embayment

    Science.gov (United States)

    Chiu, S.; Langston, C. A.; Withers, M.

    2005-12-01

    S body waves from microearthquakes in the New Madrid Seismic Zone (NMSZ) are investigated at selected broadband station sites to understand wave propagation through the Mississippi embayment sediments. Earthquake body waveforms display distinctive features that constrain the nature of the body wave local site response and wave propagation within the unconsolidated Mississippi embayment sediments. S-wave resonance effects may infer near-site conditions. Site resonance effects change between individual receivers because of velocity heterogeneity. Travel times of observed S-phases such as S, Sp, and SsShs (the first S-wave reverberation) can be used to estimate the average S-wave slowness and Poisson's ratio within the embayment sediments. An average Poisson's ratio in the range of 0.34 to 0.45 is obtained for selected sites within the central NMSZ. Use of well log data in wave calculations shows that 1-D heterogeneity can be the first-order influence on seismic wave propagation within the Mississippi embayment sediments.

  9. Experimental Study of S-wave Propagation Through a Filled Rock Joint

    Science.gov (United States)

    Liu, Tingting; Li, Jianchun; Li, Haibo; Li, Xinping; Zheng, Yun; Liu, Hui

    2017-10-01

    This experimental study proposes a Split Shear Plates model to investigate the effects of a filled joint on S-wave attenuation. A dynamic impact is used to create frictional slip and generate an incident S-wave. The filled joint is simulated using a sand layer between two rock plates. Normal stress is applied to the filled joint, and semiconductor strain gauges are arranged on the two plates to measure the strain. Verification tests are conducted to validate the reliability of the experimental results. A series of tests is performed to investigate the influence of the normal stress, filled thickness and particle size of the filling materials on the S-wave propagation. The transmission coefficients of the filled joints are smaller than those of the non-filled joints because of the attenuation associated with the filling materials. Additionally, the transmission coefficients exhibit a stronger correlation with the normal stress than with the filled thickness or particle size. The transmission coefficients increase at a decreasing rate as normal pressure increases.

  10. Knowledge Gaps

    DEFF Research Database (Denmark)

    Lyles, Marjorie; Pedersen, Torben; Petersen, Bent

    2003-01-01

    , assimilating, and utilizing knowledge - are crucial determinants ofknowledge gap elimination. In contrast, the two factors deemed essential in traditionalinternationalization process theory - elapsed time of operations and experientiallearning - are found to have no or limited effect.Key words......: Internationalization, knowledge gap, absorptive capacity, learning box....

  11. Photonic Crystals Engineering For Light Manipulation: Low Symmetry, Graded Index and Parity Time Symmetry

    CERN Document Server

    Turduev, Mirbek

    2016-01-01

    The great interest to the two and three dimensionally periodic structures, called photonic crystals (PCs), has begun with the pioneer works of Yablonovitch and John as one can efficiently control the propagation of the electromagnetic (EM) waves in the same manner with semiconductors that affect the electron conduction. One of the main peculiar properties of PCs is that they have photonic band gap in the transmission spectrum similar to electronic band gap and hence, they are able to prevent the light to propagate in certain frequency regions irrespective of the propagation direction in space. Inside the band gaps, neither optical modes nor spontaneous emissions exist. Breaking the rotational and mirror symmetries of PC unit cells provides rich dispersive features such as tilted self-collimation, and wavelength de-multiplexing effects. Another important issue in PC designs is that it is feasible to design graded index medium if the parameters of the two dimensional PCs is intentionally rearranged. That type o...

  12. Geometry and symmetry

    CERN Document Server

    Yale, Paul B

    2012-01-01

    This book is an introduction to the geometry of Euclidean, affine, and projective spaces with special emphasis on the important groups of symmetries of these spaces. The two major objectives of the text are to introduce the main ideas of affine and projective spaces and to develop facility in handling transformations and groups of transformations. Since there are many good texts on affine and projective planes, the author has concentrated on the n-dimensional cases.Designed to be used in advanced undergraduate mathematics or physics courses, the book focuses on ""practical geometry,"" emphasi

  13. Leadership, power and symmetry

    DEFF Research Database (Denmark)

    Spaten, Ole Michael

    2016-01-01

    Research publications concerning managers who coach their own employees are barely visible despite its wide- spread use in enterprises (McCarthy & Milner, 2013; Gregory & Levy, 2011; Crabb, 2011). This article focuses on leadership, power and moments of symmetry in the coaching relationship...... regarding managers coaching their employees and it is asked; what contributes to coaching of high quality when one reflects on the power aspect as being immanent? Fourteen middle managers coached five of their employees, and all members of each party wrote down cues and experiences immediately after each...

  14. Mirror symmetry II

    CERN Document Server

    Greene, Brian R

    1997-01-01

    Mirror symmetry has undergone dramatic progress during the last five years. Tremendous insight has been gained on a number of key issues. This volume surveys these results. Some of the contributions in this work have appeared elsewhere, while others were written specifically for this collection. The areas covered are organized into 4 sections, and each presents papers by both physicists and mathematicians. This volume collects the most important developments that have taken place in mathematical physics since 1991. It is an essential reference tool for both mathematics and physics libraries and for students of physics and mathematics.

  15. Groups and symmetry

    CERN Document Server

    Farmer, David W

    1995-01-01

    In most mathematics textbooks, the most exciting part of mathematics-the process of invention and discovery-is completely hidden from the reader. The aim of Groups and Symmetry is to change all that. By means of a series of carefully selected tasks, this book leads readers to discover some real mathematics. There are no formulas to memorize; no procedures to follow. The book is a guide: Its job is to start you in the right direction and to bring you back if you stray too far. Discovery is left to you. Suitable for a one-semester course at the beginning undergraduate level, there are no prerequ

  16. Gap Resolution

    Energy Technology Data Exchange (ETDEWEB)

    2017-04-25

    Gap Resolution is a software package that was developed to improve Newbler genome assemblies by automating the closure of sequence gaps caused by repetitive regions in the DNA. This is done by performing the follow steps:1) Identify and distribute the data for each gap in sub-projects. 2) Assemble the data associated with each sub-project using a secondary assembler, such as Newbler or PGA. 3) Determine if any gaps are closed after reassembly, and either design fakes (consensus of closed gap) for those that closed or lab experiments for those that require additional data. The software requires as input a genome assembly produce by the Newbler assembler provided by Roche and 454 data containing paired-end reads.

  17. Heavy-quark spin symmetry for charmed and strange baryon resonances

    Energy Technology Data Exchange (ETDEWEB)

    Romanets, Olena, E-mail: o.romanets@rug.nl [Theory Group, KVI, University of Groningen, Zernikelaan 25, 9747 AA Groningen (Netherlands); Tolos, Laura [Instituto de Ciencias del Espacio (IEEC/CSIC), Campus Universitat Autònoma de Barcelona, Facultat de Ciències, Torre C5, E-08193 Bellaterra (Barcelona) (Spain); Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe University, Ruth-Moufang-Str. 1, 60438 Frankfurt am Main (Germany); García-Recio, Carmen [Departamento de Física Atómica, Molecular y Nuclear, and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, E-18071 Granada (Spain); Nieves, Juan [Instituto de Física Corpuscular (centro mixto CSIC-UV), Institutos de Investigación de Paterna, Aptdo. 22085, 46071 Valencia (Spain); Salcedo, Lorenzo Luis [Departamento de Física Atómica, Molecular y Nuclear, and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, E-18071 Granada (Spain); Timmermans, Rob [Theory Group, KVI, University of Groningen, Zernikelaan 25, 9747 AA Groningen (Netherlands)

    2013-09-20

    We study charmed and strange odd-parity baryon resonances that are generated dynamically by a unitary baryon–meson coupled-channels model which incorporates heavy-quark spin symmetry. This is accomplished by extending the SU(3) Weinberg–Tomozawa chiral Lagrangian to SU(8) spin-flavor symmetry plus a suitable symmetry breaking. The model generates resonances with negative parity from the s-wave interaction of pseudoscalar and vector mesons with 1/2{sup +} and 3/2{sup +} baryons in all the isospin, spin, and strange sectors with one, two, and three charm units. Some of our results can be identified with experimental data from several facilities, such as the CLEO, Belle, or BaBar Collaborations, as well as with other theoretical models, whereas others do not have a straightforward identification and require the compilation of more data and also a refinement of the model.

  18. Large sonic band gaps in 12-fold quasicrystals

    Science.gov (United States)

    Lai, Yun; Zhang, Xiangdong; Zhang, Zhao-Qing

    2002-05-01

    The sonic band-gap structures of 12-fold symmetry quasicrystals consisting of rigid cylinders in air are investigated by using the multiple scattering method. Large full gaps are found in this system owing to its high symmetry. At filling fractions between 0.2 and 0.4, this 12-fold square-triangle tiling is much better for the realization of sonic band gaps than the square or triangular lattice. This makes the 12-fold quasicrystal a promising structure for acoustic-wave band-gap materials.

  19. Symmetry in Complex Networks

    Directory of Open Access Journals (Sweden)

    Angel Garrido

    2011-01-01

    Full Text Available In this paper, we analyze a few interrelated concepts about graphs, such as their degree, entropy, or their symmetry/asymmetry levels. These concepts prove useful in the study of different types of Systems, and particularly, in the analysis of Complex Networks. A System can be defined as any set of components functioning together as a whole. A systemic point of view allows us to isolate a part of the world, and so, we can focus on those aspects that interact more closely than others. Network Science analyzes the interconnections among diverse networks from different domains: physics, engineering, biology, semantics, and so on. Current developments in the quantitative analysis of Complex Networks, based on graph theory, have been rapidly translated to studies of brain network organization. The brain's systems have complex network features—such as the small-world topology, highly connected hubs and modularity. These networks are not random. The topology of many different networks shows striking similarities, such as the scale-free structure, with the degree distribution following a Power Law. How can very different systems have the same underlying topological features? Modeling and characterizing these networks, looking for their governing laws, are the current lines of research. So, we will dedicate this Special Issue paper to show measures of symmetry in Complex Networks, and highlight their close relation with measures of information and entropy.

  20. Applications of chiral symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Pisarski, R.D.

    1995-03-01

    The author discusses several topics in the applications of chiral symmetry at nonzero temperature. First, where does the rho go? The answer: up. The restoration of chiral symmetry at a temperature T{sub {chi}} implies that the {rho} and a{sub 1} vector mesons are degenerate in mass. In a gauged linear sigma model the {rho} mass increases with temperature, m{sub {rho}}(T{sub {chi}}) > m{sub {rho}}(0). The author conjectures that at T{sub {chi}} the thermal {rho} - a{sub 1}, peak is relatively high, at about {approximately}1 GeV, with a width approximately that at zero temperature (up to standard kinematic factors). The {omega} meson also increases in mass, nearly degenerate with the {rho}, but its width grows dramatically with temperature, increasing to at least {approximately}100 MeV by T{sub {chi}}. The author also stresses how utterly remarkable the principle of vector meson dominance is, when viewed from the modern perspective of the renormalization group. Secondly, he discusses the possible appearance of disoriented chiral condensates from {open_quotes}quenched{close_quotes} heavy ion collisions. It appears difficult to obtain large domains of disoriented chiral condensates in the standard two flavor model. This leads to the last topic, which is the phase diagram for QCD with three flavors, and its proximity to the chiral critical point. QCD may be very near this chiral critical point, and one might thereby generated large domains of disoriented chiral condensates.

  1. In search of symmetry lost

    CERN Multimedia

    Wilczek, Frank

    2004-01-01

    Powerful symmetry principles have guided physicists in their quest for nature's fundamental laws. The successful gauge theory of electroweak interactions postulates a more extensive symmetry for its equations than are manifest in the world (8 pages) Powerful symmetry principles have guided physicists in their quest for nature's fundamental laws. The successful gauge theory of electroweak interactions postulates a more extensive symmetry for its equations than are manifest in the world. The discrepancy is ascribed to a pervasive symmetry-breaking field, which fills all space uniformly, rendering the Universe a sort of exotic superconductor. So far, the evidence for these bold ideas is indirect. But soon the theory will undergo a critical test depending on whether the quanta of this symmetry-breaking field, the so-called Higgs particles, are produced at the Large Hadron Collider (due to begin operation in 2007).

  2. Sensitivity analysis of P-waves and S-waves to gas hydrate in the Shenhu area using OBS

    Science.gov (United States)

    Xing, Lei; Liu, Xueqin; Zhang, Jin; Liu, Huaishan; Zhang, Jing; Li, Zizheng; Wang, Jianhua

    2018-02-01

    Compared to towed streamers, ocean-bottom seismometers (OBS) obtain both S-wave data and richer wavefield information. In this paper, the induced polarization method is used to conduct wavefield separation on OBS data obtained from the Shenhu area in the South China Sea. A comparison of the changes in P- and S-waves, and a comprehensive analysis of geological factors within the area, enable analysis and description of the occurrence of natural gas hydrate in the study area. Results show an increase in P-wave velocity when natural gas hydrate exists in the formation, whereas the S-wave velocity remains almost constant, as S-waves can only propagate through the rock skeleton. Therefore, the bottom-simulating reflection (BSR) response of the P-wave is better than that of the S-wave in the frequency analysis profile. In a wide-angle section, the refractive wave of the hydrate layer is evident when using P-wave components but identification is difficult with S-wave components. This velocity model illustrates the sensitivity of P- and S-wave components to gas hydrate. The use of this polarization method and results of analysis provide technical and theoretical support for research on hydrate deposits and other geological features in the Shenhu area.

  3. Symmetries of relativistic world lines

    Science.gov (United States)

    Koch, Benjamin; Muñoz, Enrique; Reyes, Ignacio A.

    2017-10-01

    Symmetries are essential for a consistent formulation of many quantum systems. In this paper we discuss a fundamental symmetry, which is present for any Lagrangian term that involves x˙2. As a basic model that incorporates the fundamental symmetries of quantum gravity and string theory, we consider the Lagrangian action of the relativistic point particle. A path integral quantization for this seemingly simple system has long presented notorious problems. Here we show that those problems are overcome by taking into account the additional symmetry, leading directly to the exact Klein-Gordon propagator.

  4. The conservation of orbital symmetry

    CERN Document Server

    Woodward, R B

    2013-01-01

    The Conservation of Orbital Symmetry examines the principle of conservation of orbital symmetry and its use. The central content of the principle was that reactions occur readily when there is congruence between orbital symmetry characteristics of reactants and products, and only with difficulty when that congruence does not obtain-or to put it more succinctly, orbital symmetry is conserved in concerted reaction. This principle is expected to endure, whatever the language in which it may be couched, or whatever greater precision may be developed in its application and extension. The book ope

  5. Quarks, baryons and chiral symmetry

    CERN Document Server

    Hosaka, Atsushi

    2001-01-01

    This book describes baryon models constructed from quarks, mesons and chiral symmetry. The role of chiral symmetry and of quark model structure with SU(6) spin-flavor symmetry are discussed in detail, starting from a pedagogic introduction. Emphasis is placed on symmetry aspects of the theories. As an application, the chiral bag model is studied for nucleon structure, where important methods of theoretical physics, mostly related to the semiclassical approach for a system of strong interactions, are demonstrated. The text is more practical than formal; tools and ideas are explained in detail w

  6. A photonic thermalization gap in disordered lattices

    CERN Document Server

    Kondakci, H E; Saleh, B E A

    2016-01-01

    The formation of gaps -- forbidden ranges in the values of a physical parameter -- is a ubiquitous feature of a variety of physical systems: from energy bandgaps of electrons in periodic lattices and their analogs in photonic, phononic, and plasmonic systems to pseudo energy gaps in aperiodic quasicrystals. Here, we report on a `thermalization' gap for light propagating in finite disordered structures characterized by disorder-immune chiral symmetry -- the appearance of the eigenvalues and eigenvectors in skew-symmetric pairs. In this class of systems, the span of sub- thermal photon statistics is inaccessible to input coherent light, which -- once the steady state is reached -- always emerges with super-thermal statistics no matter how small the disorder level. We formulate an independent constraint that must be satisfied by the input field for the chiral symmetry to be `activated' and the gap to be observed. This unique feature enables a new form of photon-statistics interferometry: the deterministic tuning...

  7. Mythic gaps

    Directory of Open Access Journals (Sweden)

    William Hansen

    2014-11-01

    Full Text Available Different kinds of omissions sometimes occur, or are perceived to occur, in traditional narratives and in tradition-inspired literature. A familiar instance is when a narrator realizes that he or she does not fully remember the story that he or she has begun to tell, and so leaves out part of it, which for listeners may possibly result in an unintelligible narrative. But many instances of narrative gap are not so obvious. From straightforward, objective gaps one can distinguish less-obvious subjective gaps: in many cases narrators do not leave out anything crucial or truly relevant from their exposition, and yet readers perceive gaps and take steps to fill them. The present paper considers four examples of subjective gaps drawn from ancient Greek literature (the Pandora myth, ancient Roman literature (the Pygmalion legend, ancient Hebrew literature (the Joseph legend, and early Christian literature (the Jesus legend. I consider the quite varied ways in which interpreters expand the inherited texts of these stories, such as by devising names, manufacturing motives, creating backstories, and in general filling in biographical ellipses. Finally, I suggest an explanation for the phenomenon of subjective gaps, arguing that, despite their variety, they have a single cause.

  8. Orientifolds and Mirror Symmetry

    CERN Document Server

    Brunner, I; Brunner, Ilka; Hori, Kentaro

    2004-01-01

    We study parity symmetries and crosscap states in classes of N=2 supersymmetric quantum field theories in 1+1 dimensions, including non-linear sigma models, gauged WZW models, Landau-Ginzburg models, and linear sigma models. The parity anomaly and its cancellation play important roles in many of them. The case of the N=2 minimal model are studied in complete detail, from all three realizations -- gauged WZW model, abstract RCFT, and LG models. We also identify mirror pairs of orientifolds, extending the correspondence between symplectic geometry and algebraic geometry by including unorientable worldsheets. Through the analysis in various models and comparison in the overlapping regimes, we obtain a global picture of orientifolds and D-branes.

  9. Holography without translational symmetry

    CERN Document Server

    Vegh, David

    2013-01-01

    We propose massive gravity as a holographic framework for describing a class of strongly interacting quantum field theories with broken translational symmetry. Bulk gravitons are assumed to have a Lorentz-breaking mass term as a substitute for spatial inhomogeneities. This breaks momentum-conservation in the boundary field theory. At finite chemical potential, the gravity duals are charged black holes in asymptotically anti-de Sitter spacetime. The conductivity in these systems generally exhibits a Drude peak that approaches a delta function in the massless gravity limit. Furthermore, the optical conductivity shows an emergent scaling law: $|\\sigma(\\omega)| \\approx {A \\over \\omega^{\\alpha}} + B$. This result is consistent with that found earlier by Horowitz, Santos, and Tong who introduced an explicit inhomogeneous lattice into the system.

  10. Pairing gaps in nucleonic superfluids

    Energy Technology Data Exchange (ETDEWEB)

    Chen, J.M.C. (McDonnell Center for the Space Sciences and Dept. of Physics, Washington Univ., St. Louis, MO (United States)); Clark, J.W. (McDonnell Center for the Space Sciences and Dept. of Physics, Washington Univ., St. Louis, MO (United States)); Dave, R.D. (McDonnell Center for the Space Sciences and Dept. of Physics, Washington Univ., St. Louis, MO (United States)); Khodel, V.V. (McDonnell Center for the Space Sciences and Dept. of Physics, Washington Univ., St. Louis, MO (United States))

    1993-04-05

    Singlet S-wave nucleonic superfluids are studied within a microscopic many-body theory that incorporates explicit spatial correlations due to strong short-range repulsive forces as well as the momentum-space pairing correlations of BCS theory. The theory is formulated within the method of correlated basis functions (CBF). Within this scheme, there results a nonlinear problem for the superfluid energy gap that is identical in form to the gap problem of conventional BCS theory. However, the input single-particle energies and pairing matrix elements are dressed by the short-range spatial correlations and accordingly incorporate an important class of medium corrections. The effective pairing force of the theory is finite even if the bare two-nucleon potential contains an infinitely hard core; both the pairing matrix elements and single-particle energies are to be constructed from normal-state CBF matrix elements and may be evaluated by cluster-expansion techniques. The theory is explicated and applied at a variational level that is equivalent to the leading order of a CBF superstate perturbation theory. New results are presented for the [sup 1]S[sub 0] pairing gap [Delta][sub kF] in pure neutron matter at densities relevant to the inner crust of a neutron star, based on a simplified version of the Reid soft-core interaction and spin-dependent spatial correlations optimized in the correlated normal state. Careful considering is given to the treatment of the gap equation at large intermediate-state momenta. The variational gap function evaluated at the Fermi surface, [Delta][sub F], is found to be larger than predicted in earlier work. Estimates of the suppression of the gap due to polarization processes (and other particle-particle and hole-irreducible medium effects of higher order within CBF superstate perturbation theory) yield values of [Delta][sub kF].

  11. S-wave K- pi+ system in D+ ---> K- pi+ pi+ decays from Fermilab E791

    Energy Technology Data Exchange (ETDEWEB)

    Meadows, B.T.; /Cincinnati U.

    2005-06-01

    A new approach to the analysis of three body decays is presented. Model-independent results are obtained for the S-wave K{pi} amplitude as a function of K{pi} invariant mass. These are compared with results from K{sup -}{pi}{sup +} elastic scattering, and the prediction of the Watson theorem, that the phase behavior be the same below K{eta}' threshold, is tested. Contributions from I = 1/2 and I = 3/2 are not resolved in this study. If I = 1/2 dominates, however, the Watson theorem does not describe these data well.

  12. The s-Wave Neutron Strength Function in the Deformed Region

    OpenAIRE

    Izumi, FURUOYA; Ryuzo, NAKASIMA; Department of Physics, Hosei University

    1983-01-01

    The effect of the doorway states on the s-wave neutron strength function of the deformed nucleus is examined. It is found that the shape of the 4-s giant resonance in the strength function is reproduced fairly well by both effects of the doorway states and the coupled channels. In particular, the irregular hump ranging from A=160 to A=170 cannot be interpreted by coupled channel calculation alone but by additional effect of the doorway states. As an example of the isotopic trend, the numerica...

  13. GAP Analysis Program (GAP) Raster

    Data.gov (United States)

    Kansas Data Access and Support Center — The Kansas GAP Land Cover database depicts 43 land cover classes for the state of Kansas. The database was generated using a two-stage hybrid classification of...

  14. Perturbed bifurcations in the BCS gap equation

    DEFF Research Database (Denmark)

    Spathis, P. N.; Sørensen, Mads Peter; Lazarides, Nickos

    1992-01-01

    The anisotropic BCS gap equation is applied to a tight-binding model of layered high-temperature superconductors. The possible solutions have s-, d-, and mixed s- and d-wave symmetries using nearest-neighbor intralayer singlet pairing interaction of the same strength in the x and y directions. Th...

  15. Strong Coupling of a Quantum Oscillator to a Flux Qubit at Its Symmetry Point

    NARCIS (Netherlands)

    Fedorov, A.; Feofanov, A.K.; Macha, P.; Forn-Díaz, P.; Harmans, C.J.P.M.; Mooij, J.E.

    2010-01-01

    A flux qubit biased at its symmetry point shows a minimum in the energy splitting (the gap), providing protection against flux noise. We have fabricated a qubit of which the gap can be tuned fast and have coupled this qubit strongly to an LC oscillator. We show full spectroscopy of the

  16. Shape analysis with subspace symmetries

    KAUST Repository

    Berner, Alexander

    2011-04-01

    We address the problem of partial symmetry detection, i.e., the identification of building blocks a complex shape is composed of. Previous techniques identify parts that relate to each other by simple rigid mappings, similarity transforms, or, more recently, intrinsic isometries. Our approach generalizes the notion of partial symmetries to more general deformations. We introduce subspace symmetries whereby we characterize similarity by requiring the set of symmetric parts to form a low dimensional shape space. We present an algorithm to discover subspace symmetries based on detecting linearly correlated correspondences among graphs of invariant features. We evaluate our technique on various data sets. We show that for models with pronounced surface features, subspace symmetries can be found fully automatically. For complicated cases, a small amount of user input is used to resolve ambiguities. Our technique computes dense correspondences that can subsequently be used in various applications, such as model repair and denoising. © 2010 The Author(s).

  17. Discrete symmetries in the MSSM

    Energy Technology Data Exchange (ETDEWEB)

    Schieren, Roland

    2010-12-02

    The use of discrete symmetries, especially abelian ones, in physics beyond the standard model of particle physics is discussed. A method is developed how a general, abelian, discrete symmetry can be obtained via spontaneous symmetry breaking. In addition, anomalies are treated in the path integral approach with special attention to anomaly cancellation via the Green-Schwarz mechanism. All this is applied to the minimal supersymmetric standard model. A unique Z{sup R}{sub 4} symmetry is discovered which solves the {mu}-problem as well as problems with proton decay and allows to embed the standard model gauge group into a simple group, i.e. the Z{sup R}{sub 4} is compatible with grand unification. Also the flavor problem in the context of minimal flavor violation is addressed. Finally, a string theory model is presented which exhibits the mentioned Z{sup R}{sub 4} symmetry and other desirable features. (orig.)

  18. Relativistic corrections to the form factors of Bc into S -wave charmonium

    Science.gov (United States)

    Zhu, Ruilin; Ma, Yan; Han, Xin-Ling; Xiao, Zhen-Jun

    2017-05-01

    We investigate the form factors of Bc meson into S -wave charmonium within the nonrelativistic QCD effective theory and obtain the next-to-leading order relativistic corrections to the form factors, where both the Bc meson and the charmonium are treated as the nonrelativistic bound states. Treating the charm quark as a light quark in the limit mc/mb→0 , some form factors are identical at the maximum recoil point, which are consistent with the predictions in the heavy-quark effective theory and the large-energy effective theory. Considering that the branching ratios of Bc+→J /ψ Ds+ and Bc+→J /ψ Ds*+ have been measured by the LHCb and ATLAS Collaborations recently, we employ the form factors of Bc meson into S -wave charmonium at the next-to-leading order accuracy to these two decay channels and obtain more precise predictions of their decay rates. Numerical results indicate that the factorizable diagrams dominate the contribution in these two channels, while the color-suppressed and the annihilation diagrams contribute less than 10 percent. Our results are consistent with the LHCb and ATLAS data.

  19. Spin, mass, and symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Peskin, M.E. [Stanford Univ., CA (United States)

    1994-12-01

    When the strong interactions were a mystery, spin seemed to be just a complication on top of an already puzzling set of phenomena. But now that particle physicists have understood the strong, weak, and electromagnetic interactions, to be gauge theories, with matter built of quarks and leptons, it is recognized that the special properties of spin 1/2 and spin 1 particles have taken central role in the understanding of Nature. The lectures in this summer school will be devoted to the use of spin in unravelling detailed questions about the fundamental interactions. Thus, why not begin by posing a deeper question: Why is there spin? More precisely, why do the basic pointlike constituents of Nature carry intrinsic nonzero quanta of angular momentum? Though the authos has found no definite answer to this question, the pursuit of an answer has led through a wonderful tangle of speculations on the deep structure of Nature. Is spin constructed or is it fundamental? Is it the requirement of symmetry? In the furthest flights taken, it seems that space-time itself is too restrictive a notion, and that this must be generalized in order to gain a full appreciation of spin. In any case, there is no doubt that spin must play a central role in unlocking the mysteries of fundamental physics.

  20. Gravitation and Gauge Symmetries

    CERN Document Server

    Stewart, J

    2002-01-01

    The purpose of this book (I quote verbatim from the back cover) is to 'shed light upon the intrinsic structure of gravity and the principle of gauge invariance, which may lead to a consistent unified field theory', a very laudable aim. The content divides fairly clearly into four sections (and origins). After a brief introduction, chapters 2-6 review the 'Structure of gravity as a theory based on spacetime gauge symmetries'. This is fairly straightforward material, apparently based on a one-semester graduate course taught at the University of Belgrade for about two decades, and, by implication, this is a reasonably accurate description of its level and assumed knowledge. There follow two chapters of new material entitled 'Gravity in flat spacetime' and 'Nonlinear effects in gravity'. The final three chapters, entitled 'Supersymmetry and supergravity', 'Kaluza-Klein theory' and 'String theory' have been used for the basis of a one-semester graduate course on the unification of fundamental interactions. The boo...

  1. Symmetries in nuclear structure

    CERN Document Server

    Allaart, K; Dieperink, A

    1983-01-01

    The 1982 summer school on nuclear physics, organized by the Nuclear Physics Division of the Netherlands' Physical Society, was the fifth in a series that started in 1963. The number of students attending has always been about one hundred, coming from about thirty countries. The theme of this year's school was symmetry in nuclear physics. This book covers the material presented by the enthusi­ astic speakers, who were invited to lecture on this subject. We think they have succeeded in presenting us with clear and thorough introductory talks at graduate or higher level. The time schedule of the school and the location allowed the participants to make many informal contacts during many social activities, ranging from billiards to surf board sailing. We hope and expect that the combination of a relaxed atmosphere during part of the time and hard work during most of the time, has furthered the interest in, and understanding of, nuclear physics. The organization of the summer school was made possible by substantia...

  2. Spectral theorem and partial symmetries

    Energy Technology Data Exchange (ETDEWEB)

    Gozdz, A. [University of Maria Curie-Sklodowska, Department of Mathematical Physics, Institute of Physics (Poland); Gozdz, M. [University of Maria Curie-Sklodowska, Department of Complex Systems and Neurodynamics, Institute of Informatics (Poland)

    2012-10-15

    A novel method of the decompositon of a quantum system's Hamiltonian is presented. In this approach the criterion of the decomposition is determined by the symmetries possessed by the sub-Hamiltonians. This procedure is rather generic and independent of the actual global symmetry, or the lack of it, of the full Hamilton operator. A detailed investigation of the time evolution of the various sub-Hamiltonians, therefore the change in time of the symmetry of the physical object, is presented for the case of a vibrator-plus-rotor model. Analytical results are illustrated by direct numerical calculations.

  3. Discrete symmetries from hidden sectors

    Energy Technology Data Exchange (ETDEWEB)

    Anastasopoulos, Pascal [Institut für Theoretische Physik, Technische Universität Wien,A-1040 Vienna (Austria); Richter, Robert [II. Institut für Theoretische Physik, Hamburg University,Hamburg (Germany); Schellekens, A.N. [NIKHEF,Science Park 105, 1098 XG Amsterdam (Netherlands); IMAPP, Radboud Universiteit Nijmegen,Nijmegen (Netherlands); Instituto de Física Fundamental, CSIC,Madrid (Spain)

    2015-06-29

    We study the presence of abelian discrete symmetries in globally consistent orientifold compactifications based on rational conformal field theory. We extend previous work http://dx.doi.org/10.1016/j.nuclphysb.2012.08.008 by allowing the discrete symmetries to be a linear combination of U(1) gauge factors of the visible as well as the hidden sector. This more general ansatz significantly increases the probability of finding a discrete symmetry in the low energy effective action. Applied to globally consistent MSSM-like Gepner constructions we find multiple models that allow for matter parity or Baryon triality.

  4. SYMMETRY OF TWO DIMENSIONAL PATTERNS

    Directory of Open Access Journals (Sweden)

    DOBRE Daniel

    2014-11-01

    Full Text Available This paper identifies geometric concepts and constructions of symmetrical patterns which are of great value to design practitioners. Particular attention is focused on geometric symmetry as the basis of an analytical tool to examine designs in different cultural contexts. In two dimensions, there are 17 wallpaper groups, produced by translations in two directions, reflections, inversions and rotations. Plane patterns can be naturally classified according to the symmetries they admit. In this paper the symmetries of the plane, and the resulting classification of patterns, are given and described. Illustrations of regularly repeating designs are presented.

  5. Astroparticle tests of Lorentz symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, Jorge [Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2016-07-01

    Lorentz symmetry is a cornerstone of modern physics. As the spacetime symmetry of special relativity, Lorentz invariance is a basic component of the standard model of particle physics and general relativity, which to date constitute our most successful descriptions of nature. Deviations from exact symmetry would radically change our view of the universe and current experiments allow us to test the validity of this assumption. In this talk, I describe effects of Lorentz violation in cosmic rays and gamma rays that can be studied in current observatories.

  6. Nuclear tetrahedral symmetry: possibly present throughout the periodic table.

    Science.gov (United States)

    Dudek, J; Goźdź, A; Schunck, N; Miśkiewicz, M

    2002-06-24

    More than half a century after the fundamental, spherical shell structure in nuclei had been established, theoretical predictions indicated that the shell gaps comparable or even stronger than those at spherical shapes may exist. Group-theoretical analysis supported by realistic mean-field calculations indicate that the corresponding nuclei are characterized by the TD(d) ("double-tetrahedral") symmetry group. Strong shell-gap structure is enhanced by the existence of the four-dimensional irreducible representations of TD(d); it can be seen as a geometrical effect that does not depend on a particular realization of the mean field. Possibilities of discovering the TD(d) symmetry in experiment are discussed.

  7. Insulators and metals with topological order and discrete symmetry breaking

    Science.gov (United States)

    Chatterjee, Shubhayu; Sachdev, Subir

    2017-05-01

    Numerous experiments have reported discrete symmetry breaking in the high-temperature pseudogap phase of the hole-doped cuprates, including breaking of one or more of lattice rotation, inversion, and time-reversal symmetries. In the absence of translational symmetry breaking or topological order, these conventional order parameters cannot explain the gap in the charged fermion excitation spectrum in the antinodal region. Zhao et al. [L. Zhao, D. H. Torchinsky, H. Chu, V. Ivanov, R. Lifshitz, R. Flint, T. Qi, G. Cao, and D. Hsieh, Nat. Phys. 12, 32 (2016), 10.1038/nphys3517] and Jeong et al. [J. Jeong, Y. Sidis, A. Louat, V. Brouet, and P. Bourges, Nat. Commun. 8, 15119 (2017), 10.1038/ncomms15119] have also reported inversion and time-reversal symmetry breaking in insulating Sr2IrO4 similar to that in the metallic cuprates, but coexisting with Néel order. We extend an earlier theory of topological order in insulators and metals, in which the topological order combines naturally with the breaking of these conventional discrete symmetries. We find translationally invariant states with topological order coexisting with both Ising-nematic order and spontaneous charge currents. The link between the discrete broken symmetries and the topological-order-induced pseudogap explains why the broken symmetries do not survive in the confining phases without a pseudogap at large doping. Our theory also connects to the O(3) nonlinear sigma model and CP1 descriptions of quantum fluctuations of the Néel order. In this framework, the optimal doping criticality of the cuprates is primarily associated with the loss of topological order.

  8. Upper-mantle velocities below the Scandinavian Mountains from P- and S- wave traveltime tomography

    DEFF Research Database (Denmark)

    Hejrani, Babak; Balling, N.; Jacobsen, B. H.

    2017-01-01

    More than 20000 arrival-times of teleseismic P- and S-waves were measured over a period of more than 10 years in five separate temporary and two permanent seismic networks covering the Scandinavian (Scandes) Mountains and adjacent areas of the Baltic Shield. The relative traveltime residuals were...... inverted to 3D tomograms of P- and S- velocities and the VP/VS ratio. Resolution analysis documents that good 3D resolution is available under the dense network south of 64° latitude (Southern Scandes Mountains), and patchier, but highly useful resolution is available further north, where station coverage...... is more uneven. A pronounced upper-mantle velocity boundary (UMVB), transecting the study region is defined. It runs from SE Norway (east of the Oslo Graben) across the mountains to the Norwegian coast near Trondheim (around the Møre-Trøndelag Fault Complex), from where it follows the coast and runs...

  9. Analytical calculation for the gluon fragmentation into spin-triplet S -wave quarkonium

    Science.gov (United States)

    Zhang, Peng; Ma, Yan-Qing; Chen, Qian; Chao, Kuang-Ta

    2017-11-01

    Fragmentation is the dominant mechanism for hadron production with high transverse momentum. For spin-triplet S -wave heavy quarkonium production, contribution of gluon fragmenting to color-singlet channel has been numerically calculated since 1993. However, there is still no analytic expression available up to now because of its complexity. In this paper, we calculate both polarization-summed and polarized fragmentation functions of gluon fragmenting to a heavy quark-antiquark pair with quantum number S3 1 [1 ] . Our calculations are performed in two different frameworks. One is the widely used nonrelativistic QCD factorization, and the other is the newly proposed soft gluon factorization. In either case, we calculate at both leading order and next-to-leading order in velocity expansion. All of our final results are presented in terms of compact analytic expressions.

  10. Upper mantle thermal variations beneath the Transantarctic Mountains inferred from teleseismic S-wave attenuation

    Science.gov (United States)

    Lawrence, Jesse F.; Wiens, Douglas A.; Nyblade, Andrew A.; Anandakrishan, Sridhar; Shore, Patrick J.; Voigt, Donald

    2006-02-01

    This study examines teleseismic S-wave attenuation variations between the Ross Sea in West Antarctica and Vostok Subglacial Highlands in East Antarctica. These analyses indicate that δt* is ~1 second greater beneath the Ross Sea than East Antarctica, with the transition occurring beneath the Transantarctic Mountains. While the structure is non-unique, low attenuation beneath East Antarctica is consistent with thick subcontinental lithosphere (>=250 km) and negligible asthenosphere. In contrast, the Ross Sea possesses a thin lithosphere underlain by thick, highly anelastic asthenosphere. Independent temperature estimates from velocity and quality factor indicate that the mantle is 200-400°C colder beneath East Antarctica than the Ross Sea between 80 and 220 km depth. The temperature variation beneath the Transantarctic Mountains may have assisted in the asymmetric uplift of the mountains. Attenuation and velocity anomalies within East Antarctica may delineate regions of elevated temperature, representing recently modified sections between older lithospheric blocks.

  11. Upper-mantle P- and S- wave velocities across the Northern Tornquist Zone from traveltime tomography

    DEFF Research Database (Denmark)

    Hejrani, Babak; Balling, N.; Jacobsen, B. H.

    2015-01-01

    This study presents P- and S-wave velocity variations for the upper mantle in southern Scandinavia and northern Germany based on teleseismic traveltime tomography. Tectonically, this region includes the entire northern part of the prominent Tornquist Zone which follows along the transition from old...... Precambrian shield units to the east to younger Phanerozoic deep sedimentary basins to the southwest. We combine data from several separate temporary arrays/profiles (276 stations) deployed over a period of about 15 yr and permanent networks (31 stations) covering the areas of Denmark, northern Germany......, southern Sweden and southern Norway. By performing an integrated P- and S-traveltime analysis, we obtain the first high-resolution combined 3-D VP and VS models, including variations in the VP/VS ratio, for the whole of this region of study. Relative station mean traveltime residuals vary within ±1 s for P...

  12. Non-overlapped P- and S-wave Poynting vectors and its solution on Grid Method

    KAUST Repository

    Lu, Yong Ming

    2017-12-12

    Poynting vector represents the local directional energy flux density of seismic waves in geophysics. It is widely used in elastic reverse time migration (RTM) to analyze source illumination, suppress low-wavenumber noise, correct for image polarity and extract angle-domain common imaging gather (ADCIG). However, the P and S waves are mixed together during wavefield propagation such that the P and S energy fluxes are not clean everywhere, especially at the overlapped points. In this paper, we use a modified elastic wave equation in which the P and S vector wavefields are naturally separated. Then, we develop an efficient method to evaluate the separable P and S poynting vectors, respectively, based on the view that the group velocity and phase velocity have the same direction in isotropic elastic media. We furthermore formulate our method using an unstructured mesh based modeling method named the grid method. Finally, we verify our method using two numerical examples.

  13. SYMMETRY OF TWO DIMENSIONAL PATTERNS

    OpenAIRE

    DOBRE Daniel

    2014-01-01

    This paper identifies geometric concepts and constructions of symmetrical patterns which are of great value to design practitioners. Particular attention is focused on geometric symmetry as the basis of an analytical tool to examine designs in different cultural contexts. In two dimensions, there are 17 wallpaper groups, produced by translations in two directions, reflections, inversions and rotations. Plane patterns can be naturally classified according to the symmetries they admit. In this ...

  14. Investigating Near Surface S-Wave Velocity Properties Using Ambient Noise in Southwestern Taiwan

    Directory of Open Access Journals (Sweden)

    Chun-Hsiang Kuo

    2015-01-01

    Full Text Available Ambient noise is typically used to estimate seismic site effects and velocity profiles instead of earthquake recordings, especially in areas with limited seismic data. The dominant Horizontal to Vertical Spectral Ratio (HVSR frequency of ambient noise is correlated to Vs30, which is the average S-wave velocity in the top 30 m. Vs30 is a widely used parameter for defining seismic amplification in earthquake engineering. HVSR can detect the vertical discontinuity of velocities, that is, the interfaces between hard bedrock and soft sediments. In southwestern Taiwan most strong motion stations are located in the plains and show a dominant frequency lower than 3 Hz. Several stations near the coast have low dominant frequencies of less than 1 Hz. The dominant frequencies are higher than 4 Hz at piedmont stations. The stations in the mountains with dominant frequencies over 8 Hz are typically located on very hard sites. This study analyzed the HVSR characteristics under different seismic site conditions considering the Vs30 from previous study (Kuo et al. 2012. The result implies that HVSRs are a better tool than Vs30 to classify the sites where bedrock is deeper than 30 m. Furthermore, we found a linear correlation between Vs30 and dominant HVSR frequency which could be used as a proxy of Vs30. The Vs30 map in this area was derived using the Engineering Geological Database for Taiwan Strong Motion Instrumentation Program (EGDT. The comparable distribution pattern between the dominant frequency and Vs30 demonstrate that HVSR can recognize S-wave velocity properties at the shallow subsurface.

  15. Lorentz Transformations from Intrinsic Symmetries

    Directory of Open Access Journals (Sweden)

    Sheng D. Chao

    2016-09-01

    Full Text Available We reveal the frame-exchange space-inversion (FESI symmetry and the frame-exchange time-inversion (FETI symmetry in the Lorentz transformation and propose a symmetry principle stating that the space-time transformation between two inertial frames is invariant under the FESI or the FETI transformation. In combination with the principle of relativity and the presumed nature of Euclidean space and time, the symmetry principle is employed to derive the proper orthochronous Lorentz transformation without assuming the constancy of the speed of light and specific mathematical requirements (such as group property a priori. We explicitly demonstrate that the constancy of the speed of light in all inertial frames can be derived using the velocity reciprocity property, which is a deductive consequence of the space–time homogeneity and the space isotropy. The FESI or the FETI symmetry remains to be preserved in the Galilean transformation at the non-relativistic limit. Other similar symmetry operations result in either trivial transformations or improper and/or non-orthochronous Lorentz transformations, which do not form groups.

  16. Estimation of S-wave Velocity Structures by Using Microtremor Array Measurements for Subsurface Modeling in Jakarta

    Directory of Open Access Journals (Sweden)

    Mohamad Ridwan

    2014-12-01

    Full Text Available Jakarta is located on a thick sedimentary layer that potentially has a very high seismic wave amplification. However, the available information concerning the subsurface model and bedrock depth is insufficient for a seismic hazard analysis. In this study, a microtremor array method was applied to estimate the geometry and S-wave velocity of the sedimentary layer. The spatial autocorrelation (SPAC method was applied to estimate the dispersion curve, while the S-wave velocity was estimated using a genetic algorithm approach. The analysis of the 1D and 2D S-wave velocity profiles shows that along a north-south line, the sedimentary layer is thicker towards the north. It has a positive correlation with a geological cross section derived from a borehole down to a depth of about 300 m. The SPT data from the BMKG site were used to verify the 1D S-wave velocity profile. They show a good agreement. The microtremor analysis reached the engineering bedrock in a range from 359 to 608 m as depicted by a cross section in the north-south direction. The site class was also estimated at each site, based on the average S-wave velocity until 30 m depth. The sites UI to ISTN belong to class D (medium soil, while BMKG and ANCL belong to class E (soft soil.

  17. Symmetry and symmetry breaking; Symetrie et brisure de symetrie

    Energy Technology Data Exchange (ETDEWEB)

    Balian, R. [CEA/Saclay, Direction des Sciences de la Matiere (DSM), 91 - Gif-sur-Yvette (France); Lambert, D. [Facultes Universitaires Notre-Dame de la Paix, Namur (Belgium); Brack, A. [Centre National de la Recherche Scientifique (CNRS), 45 - Orleans-la-Source (France). Centre de Biophysique Moleculaire; Englert, F. [Universite Libre de Bruxelles (Belgium). Laboratoire de Physique Theorique; Chomaz, Ph. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France); Lachieze-Rey, M. [CEA/Saclay, Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee (DAPNIA), 91 - Gif-sur-Yvette (France); Emery, E. [Ecole Polytechnique Federale, Lausanne (Switzerland); Cohen-Tannoudji, G.; Sacquin, Y

    1999-11-01

    The symmetry concept is a powerful tool for our understanding of the world. It allows a reduction of the volume of information needed to apprehend a subject thoroughly. Moreover this concept does not belong to a particular field, it is involved in the exact sciences but also in artistic matters. Living beings are characterized by a particular asymmetry: the chiral asymmetry. Although this asymmetry is visible in whole organisms, it seems it comes from some molecules that life always produce in one chirality. The weak interaction presents also the chiral asymmetry. The mass of particles comes from the breaking of a fundamental symmetry and the void could be defined as the medium showing as many symmetries as possible. The texts put together in this book show to a great extent how symmetry goes far beyond purely geometrical considerations. Different aspects of symmetry ideas are considered in the following fields: the states of matter, mathematics, biology, the laws of Nature, quantum physics, the universe, and the art of music. (A.C.) 103 refs.

  18. Symmetry and symmetry breaking. Symetrie et brisure de symetrie

    Energy Technology Data Exchange (ETDEWEB)

    Balian, R. (CEA/Saclay, Direction des Sciences de la Matiere (DSM), 91 - Gif-sur-Yvette (France)); Lambert, D. (Facultes Universitaires Notre-Dame de la Paix, Namur (Belgium)); Brack, A. (Centre National de la Recherche Scientifique (CNRS), 45 - Orleans-la-Source (France). Centre de Biophysique Moleculaire); Englert, F. (Universite Libre de Bruxelles (Belgium). Laboratoire de Physique Theorique)

    1999-01-01

    The symmetry concept is a powerful tool for our understanding of the world. It allows a reduction of the volume of information needed to apprehend a subject thoroughly. Moreover this concept does not belong to a particular field, it is involved in the exact sciences but also in artistic matters. Living beings are characterized by a particular asymmetry: the chiral asymmetry. Although this asymmetry is visible in whole organisms, it seems it comes from some molecules that life always produce in one chirality. The weak interaction presents also the chiral asymmetry. The mass of particles comes from the breaking of a fundamental symmetry and the void could be defined as the medium showing as many symmetries as possible. The texts put together in this book show to a great extent how symmetry goes far beyond purely geometrical considerations. Different aspects of symmetry ideas are considered in the following fields: the states of matter, mathematics, biology, the laws of Nature, quantum physics, the universe, and the art of music. (A.C.) 103 refs.

  19. Test of Pseudospin Symmetry in Deformed Nuclei

    OpenAIRE

    Ginocchio, J. N.; Leviatan, A.; Meng, J.; Zhou, Shan-Gui

    2003-01-01

    Pseudospin symmetry is a relativistic symmetry of the Dirac Hamiltonian with scalar and vector mean fields equal and opposite in sign. This symmetry imposes constraints on the Dirac eigenfunctions. We examine extensively the Dirac eigenfunctions of realistic relativistic mean field calculations of deformed nuclei to determine if these eigenfunctions satisfy these pseudospin symmetry constraints.

  20. Symmetry and group theory in chemistry

    CERN Document Server

    Ladd, M

    1998-01-01

    A comprehensive discussion of group theory in the context of molecular and crystal symmetry, this book covers both point-group and space-group symmetries.Provides a comprehensive discussion of group theory in the context of molecular and crystal symmetryCovers both point-group and space-group symmetriesIncludes tutorial solutions

  1. Structural symmetry and protein function.

    Science.gov (United States)

    Goodsell, D S; Olson, A J

    2000-01-01

    The majority of soluble and membrane-bound proteins in modern cells are symmetrical oligomeric complexes with two or more subunits. The evolutionary selection of symmetrical oligomeric complexes is driven by functional, genetic, and physicochemical needs. Large proteins are selected for specific morphological functions, such as formation of rings, containers, and filaments, and for cooperative functions, such as allosteric regulation and multivalent binding. Large proteins are also more stable against denaturation and have a reduced surface area exposed to solvent when compared with many individual, smaller proteins. Large proteins are constructed as oligomers for reasons of error control in synthesis, coding efficiency, and regulation of assembly. Symmetrical oligomers are favored because of stability and finite control of assembly. Several functions limit symmetry, such as interaction with DNA or membranes, and directional motion. Symmetry is broken or modified in many forms: quasisymmetry, in which identical subunits adopt similar but different conformations; pleomorphism, in which identical subunits form different complexes; pseudosymmetry, in which different molecules form approximately symmetrical complexes; and symmetry mismatch, in which oligomers of different symmetries interact along their respective symmetry axes. Asymmetry is also observed at several levels. Nearly all complexes show local asymmetry at the level of side chain conformation. Several complexes have reciprocating mechanisms in which the complex is asymmetric, but, over time, all subunits cycle through the same set of conformations. Global asymmetry is only rarely observed. Evolution of oligomeric complexes may favor the formation of dimers over complexes with higher cyclic symmetry, through a mechanism of prepositioned pairs of interacting residues. However, examples have been found for all of the crystallographic point groups, demonstrating that functional need can drive the evolution of

  2. Projected Entangled Pair States with non-Abelian gauge symmetries: An SU(2) study

    Energy Technology Data Exchange (ETDEWEB)

    Zohar, Erez, E-mail: erez.zohar@mpq.mpg.de [Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching (Germany); Wahl, Thorsten B. [Rudolf Peierls Centre for Theoretical Physics, Oxford, 1 Keble Road, OX1 3NP (United Kingdom); Burrello, Michele, E-mail: michele.burrello@mpq.mpg.de [Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching (Germany); Cirac, J. Ignacio [Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching (Germany)

    2016-11-15

    Over the last years, Projected Entangled Pair States have demonstrated great power for the study of many body systems, as they naturally describe ground states of gapped many body Hamiltonians, and suggest a constructive way to encode and classify their symmetries. The PEPS study is not only limited to global symmetries, but has also been extended and applied for local symmetries, allowing to use them for the description of states in lattice gauge theories. In this paper we discuss PEPS with a local, SU(2) gauge symmetry, and demonstrate the use of PEPS features and techniques for the study of a simple family of many body states with a non-Abelian gauge symmetry. We present, in particular, the construction of fermionic PEPS able to describe both two-color fermionic matter and the degrees of freedom of an SU(2) gauge field with a suitable truncation.

  3. 3-D P- and S-wave velocity structure along the central Alpine Fault, South Island, New Zealand

    Science.gov (United States)

    Guo, B.; Thurber, C. H.; Roecker, S. W.; Townend, J.; Rawles, C.; Chamberlain, C. J.; Boese, C. M.; Bannister, S.; Feenstra, J.; Eccles, J. D.

    2017-05-01

    The Deep Fault Drilling Project (DFDP) on the central Alpine Fault, South Island, New Zealand, has motivated a broad range of geophysical and geological studies intended to characterize the fault system in the locality of the drill site at various scales. In order to better understand the structural features of the central Alpine Fault, we have developed 3-D P- and S-wave velocity (VP and VS) models of the region by double-difference tomography using data sets from multiple seismic networks. In previous work, the quality of the S-wave model has been poor due to the small number of available S-wave picks. We have utilized a new high-accuracy automatic S-wave picker to increase the number of usable S-wave arrivals by more than a factor of two, thereby substantially improving the VS model. Compared to previous studies, our new higher-resolution VP model based on more observations shows a clear VP contrast (higher VP on the southeast hanging wall side) at depths of 5-10 km near the DFDP drill sites. With our better resolved VS model, in the same region, we detect a sharply defined high VS body (VS > 3.7 km s-1) within the hanging wall. Our earthquake relocations reveal the presence of clusters within and around low-velocity zones in the hanging wall southeast of the Alpine Fault. Together with the improved earthquake locations, the P- and S-wave tomography results reveal the Alpine Fault to be marked by a velocity contrast throughout most of the study region. The fault dips southeastwards at about 50° from 5 to 15 km depth, as inferred from the velocity structure, seismicity and observations of fault zone guided waves.

  4. Parity-time symmetry broken by point-group symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Fernández, Francisco M., E-mail: fernande@quimica.unlp.edu.ar; Garcia, Javier [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Blvd. 113 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)

    2014-04-15

    We discuss a parity-time (PT) symmetric Hamiltonian with complex eigenvalues. It is based on the dimensionless Schrödinger equation for a particle in a square box with the PT-symmetric potential V(x, y) = iaxy. Perturbation theory clearly shows that some of the eigenvalues are complex for sufficiently small values of |a|. Point-group symmetry proves useful to guess if some of the eigenvalues may already be complex for all values of the coupling constant. We confirm those conclusions by means of an accurate numerical calculation based on the diagonalization method. On the other hand, the Schrödinger equation with the potential V(x, y) = iaxy{sup 2} exhibits real eigenvalues for sufficiently small values of |a|. Point group symmetry suggests that PT-symmetry may be broken in the former case and unbroken in the latter one.

  5. S-wave \\gamma\\gamma\\to \\pi\\pi and f_0(980)\\to \\pi\\pi

    OpenAIRE

    Oller, J. A.; Roca, L.; Schat, C.

    2008-01-01

    We report on a dispersion relation for the \\gamma\\gamma\\to (\\pi\\pi)_I S-wave in isospin I emphasizing the low energy region. The f_0(980) signal that emerges in \\gamma\\gamma\\to \\pi\\pi is also discussed. Our results could be used to distinguish between different \\pi\\pi isoscalar S-wave parameterizations. We also calculate the width of the \\sigma resonance to \\gamma\\gamma and obtain the value \\Gamma(\\sigma\\to\\gamma\\gamma)=(1.68\\pm 0.15) KeV. Finally, we elaborate on the size of the f_0(980) cou...

  6. Localization of Nonlocal Symmetries and Symmetry Reductions of Burgers Equation

    Science.gov (United States)

    Wu, Jian-Wen; Lou, Sen-Yue; Yu, Jun

    2017-05-01

    The nonlocal symmetries of the Burgers equation are explicitly given by the truncated Painlevé method. The auto-Bäcklund transformation and group invariant solutions are obtained via the localization procedure for the nonlocal residual symmetries. Furthermore, the interaction solutions of the solition-Kummer waves and the solition-Airy waves are obtained. Supported by the Global Change Research Program China under Grant No. 2015CB953904, the National Natural Science Foundations of China under Grant Nos. 11435005, 11175092, and 11205092, Shanghai Knowledge Service Platform for Trustworthy Internet of Things under Grant No. ZF1213, and K. C. Wong Magna Fund in Ningbo University

  7. Big break for charge symmetry

    CERN Document Server

    Miller, G A

    2003-01-01

    Two new experiments have detected charge-symmetry breaking, the mechanism responsible for protons and neutrons having different masses. Symmetry is a crucial concept in the theories that describe the subatomic world because it has an intimate connection with the laws of conservation. The theory of the strong interaction between quarks - quantum chromodynamics - is approximately invariant under what is called charge symmetry. In other words, if we swap an up quark for a down quark, then the strong interaction will look almost the same. This symmetry is related to the concept of sup i sospin sup , and is not the same as charge conjugation (in which a particle is replaced by its antiparticle). Charge symmetry is broken by the competition between two different effects. The first is the small difference in mass between up and down quarks, which is about 200 times less than the mass of the proton. The second is their different electric charges. The up quark has a charge of +2/3 in units of the proton charge, while ...

  8. A symmetry for ɛ K

    Science.gov (United States)

    Da Rold, Leandro; Davidovich, Iván A.

    2017-10-01

    We show a symmetry that, in the context of a composite Higgs with anarchic flavor, can suppress the dominant CP violating contributions to K-\\overline{K} mixing. Based on previous extensions of SU(3) c , we consider the case in which the composite sector has a global SU(6) symmetry, spontaneously broken to a subgroup containing SU(3)×SU(3). We show that the interactions with the Standard Model can spontaneously break the remaining symmetry to the diagonal subgroup, identified with the group of color interactions, and naturally suppress ɛ K . We consider this scenario in the context of the Minimal Composite Higgs Model based on SO(5)/SO(4) for the electroweak sector. By working in the framework of 2-site models, we compute the scalar potential, determine the conditions for a successful breaking of the symmetries and calculate the spectrum of lightest states. We find that ɛ K can be suppressed and the top mass reproduced for a large region of the parameter space where the symmetries are dynamically broken. We also find a suppression of the Wilson coefficient of dipole operators, particularly interesting for the neutron dipole moments. Besides other new resonances, the model predicts the presence of a new singlet scalar state, generally lighter than the Higgs, that could have evaded detection at colliders.

  9. Asymptotic symmetries and electromagnetic memory

    Science.gov (United States)

    Pasterski, Sabrina

    2017-09-01

    Recent investigations into asymptotic symmetries of gauge theory and gravity have illuminated connections between gauge field zero-mode sectors, the corresponding soft factors, and their classically observable counterparts — so called "memories". Namely, low frequency emissions in momentum space correspond to long time integrations of the corre-sponding radiation in position space. Memory effect observables constructed in this manner are non-vanishing in typical scattering processes, which has implications for the asymptotic symmetry group. Here we complete this triad for the case of large U(1) gauge symmetries at null infinity. In particular, we show that the previously studied electromagnetic memory effect, whereby the passage of electromagnetic radiation produces a net velocity kick for test charges in a distant detector, is the position space observable corresponding to th Weinberg soft photon pole in momentum space scattering amplitudes.

  10. Symmetry analysis of cellular automata

    Energy Technology Data Exchange (ETDEWEB)

    García-Morales, V., E-mail: vmorales@ph.tum.de [Institute for Advanced Study – Technische Universität München, Lichtenbergstr. 2a, D-85748 Garching (Germany)

    2013-01-03

    By means of B-calculus [V. García-Morales, Phys. Lett. A 376 (2012) 2645] a universal map for deterministic cellular automata (CAs) has been derived. The latter is shown here to be invariant upon certain transformations (global complementation, reflection and shift). When constructing CA rules in terms of rules of lower range a new symmetry, “invariance under construction” is uncovered. Modular arithmetic is also reformulated within B-calculus and a new symmetry of certain totalistic CA rules, which calculate the Pascal simplices modulo an integer number p, is then also uncovered.

  11. Dirichlet branes and mirror symmetry

    CERN Document Server

    2009-01-01

    This is the second of two books that provide the scientific record of the school. The first book, Strings and Geometry, edited by Michael R. Douglas et al., was a proceedings volume and largely focused on the topics of manifolds holonomy and supergravity. The present volume, intended to be a monograph, covers mirror symmetry from the homological and torus fibration points of view. We hope that this volume is a natural sequel to Mirror Symmetry, written by Hoi, Katz, Klemm, Pandharipande, Thomas, Vafa, Vakil and Zaslow, which was a product of the first Clay School in the spring of 2000.

  12. Symmetry of intramolecular quantum dynamics

    CERN Document Server

    Burenin, Alexander V

    2012-01-01

    The main goal of this book is to give a systematic description of intramolecular quantum dynamics on the basis of only the symmetry principles. In this respect, the book has no analogs in the world literature. The obtained models lead to a simple, purely algebraic, scheme of calculation and are rigorous in the sense that their correctness is limited only to the correct choice of symmetry of the internal dynamics. The book is basically intended for scientists working in the field of molecular spectroscopy, quantum and structural chemistry.

  13. Symposium Symmetries in Science XIII

    CERN Document Server

    Gruber, Bruno J; Yoshinaga, Naotaka; Symmetries in Science XI

    2005-01-01

    This book is a collection of reviews and essays about the recent developments in the area of Symmetries and applications of Group Theory. Contributions have been written mostly at the graduate level but some are accessible to advanced undergraduates. The book is of interest to a wide audience and covers a broad range of topics with a strong degree of thematical unity. The book is part of a Series of books on Symmetries in Science and may be compared to the published Proceedings of the Colloquia on Group Theoretical Methods in Physics. Here, however, prevails a distinguished character for presenting extended reviews on present applications to Science, not restricted to Theoretical Physics.

  14. Segmenting Brain Tumors with Symmetry

    OpenAIRE

    Zhang, Hejia; Zhu, Xia; Willke, Theodore L.

    2017-01-01

    We explore encoding brain symmetry into a neural network for a brain tumor segmentation task. A healthy human brain is symmetric at a high level of abstraction, and the high-level asymmetric parts are more likely to be tumor regions. Paying more attention to asymmetries has the potential to boost the performance in brain tumor segmentation. We propose a method to encode brain symmetry into existing neural networks and apply the method to a state-of-the-art neural network for medical imaging s...

  15. Cosmological Reflection of Particle Symmetry

    Directory of Open Access Journals (Sweden)

    Maxim Khlopov

    2016-08-01

    Full Text Available The standard model involves particle symmetry and the mechanism of its breaking. Modern cosmology is based on inflationary models with baryosynthesis and dark matter/energy, which involves physics beyond the standard model. Studies of the physical basis of modern cosmology combine direct searches for new physics at accelerators with its indirect non-accelerator probes, in which cosmological consequences of particle models play an important role. The cosmological reflection of particle symmetry and the mechanisms of its breaking are the subject of the present review.

  16. Type-I and type-II topological nodal superconductors with s -wave interaction

    Science.gov (United States)

    Huang, Beibing; Yang, Xiaosen; Xu, Ning; Gong, Ming

    2018-01-01

    Topological nodal superconductors with protected gapless points in momentum space are generally realized based on unconventional pairings. In this work we propose a minimal model to realize these topological nodal phases with only s -wave interaction. In our model the linear and quadratic spin-orbit couplings along the two orthogonal directions introduce anisotropic effective unconventional pairings in momentum space. This model may support different nodal superconducting phases characterized by either an integer winding number in BDI class or a Z2 index in D class at the particle-hole invariant axes. In the vicinity of the nodal points the effective Hamiltonian can be described by either type-I or type-II Dirac equations, and the Lifshitz transition from type-I nodal phases to type-II nodal phases can be driven by external in-plane magnetic fields. We show that these nodal phases are robust against weak impurities, which only slightly renormalizes the momentum-independent parameters in the impurity-averaged Hamiltonian, thus these phases are possible to be realized in experiments with real semi-Dirac materials. The smoking-gun evidences to verify these phases based on scanning tunneling spectroscopy method are also briefly discussed.

  17. S-Wave Velocity Across Central Mexico Using High Resolution Surface Wave Tomography

    Science.gov (United States)

    Iglesias, A.; Clayton, R. W.; Pérez-Campos, X.; Singh, S. K.; Pacheco, J. F.; García, D.; Valdés-González, C.

    2008-12-01

    The shear wave velocity structure across central Mexico is determined by surface wave dispersion from a dense linear seismic experiment "Mesoamerican Subduction Experiment" (MASE). MASE consisted of 100 portable broadband stations deployed along a line crossing Central Mexico from the Pacific Coast to almost the Gulf of Mexico. Regional records were used to obtain Rayleigh-wave group velocity maps for periods from 5 to 50 s and they show a dramatic variation of velocity (~40%), especially for periods larger of 20 s. Local dispersion curves were reconstructed for each station and inverted to find S-wave velocity by using a simulated annealing algorithm. The results, from inversion, show a significant change, particularly in the lower crust, between the backarc, volcanic arc and forearc regions. The crust in the forearc is thicker and faster than the backarc region. Just below the active Trans Mexican Volcanic Belt (TMVB) (300 km from the coast) is presently a low velocity spot (~3.4 km/s) suggesting presence of anomalous material (probably related to a mantle wedge) as deep as 50 km. The results also show a poorly resolved slab and wedge which correspond to the ones in a model reported recently. The results are supported with consistency checks and resolution tests.

  18. Region-specific S-wave attenuation for earthquakes in northwestern Iran

    Science.gov (United States)

    Heidari, Reza; Mirzaei, Noorbakhsh

    2017-11-01

    In this study, continuous wavelet transform is applied to estimate the frequency-dependent quality factor of shear waves, Q S , in northwestern Iran. The dataset used in this study includes velocigrams of more than 50 events with magnitudes between 4.0 and 6.5, which have occurred in the study area. The CWT-based method shows a high-resolution technique for the estimation of S-wave frequency-dependent attenuation. The quality factor values are determined in the form of a power law as Q S ( f) = (147 ± 16) f 0.71 ± 0.02 and (126 ± 12) f 0.73 ± 0.02 for vertical and horizontal components, respectively, where f is between 0.9 and 12 Hz. Furthermore, in order to verify the reliability of the suggested Q S estimator method, an additional test is performed by using accelerograms of Ahar-Varzaghan dual earthquakes on August 11, 2012, of moment magnitudes 6.4 and 6.3 and their aftershocks. Results indicate that the estimated Q S values from CWT-based method are not very sensitive to the numbers and types of waveforms used (velocity or acceleration).

  19. Electrodynamics of s-Wave Superconductors Using First-Order Formalism

    Directory of Open Access Journals (Sweden)

    Naoum Karchev

    2017-06-01

    Full Text Available In this paper we give a derivation of a system of equations which generalize the London brothers and Ginzburg–Landau systems of equations, to describe the electrodynamics of s-wave superconductors. First, we consider a relativistically covariant theory in terms of gauge four-vector electromagnetic potential and scalar complex field. We use the first-order formalism to obtain the supplemented Maxwell equations for gauge-invariant electric, magnetic, four-vector fields and the modulus of the superconducting order parameter. The new four-vector field appears in some of the equations as a gauge-invariant super-current, and in other ones, while gauge invariant, as a four-vector electromagnetic potential. This dual contribution of the new four-vector field is the basis of the electrodynamics of superconductors. We focus on the system of equations with time-independent fields. The qualitative analysis shows that the applied magnetic field suppresses the superconductivity, while the applied electric field impacts oppositely, supporting it. Secondly, we consider time-dependent non-relativistic Ginzburg–Landau theory.

  20. Determination of the pion-nucleon coupling constant and s-wave scattering lengths

    CERN Document Server

    Samaranayake, V K

    1972-01-01

    Presently available values of D/sub +or-/, the real parts of the pi /sup +or-/p elastic scattering amplitudes in the forward direction in the laboratory frame, obtained by extrapolation of experimental data to the forward direction, have been fitted up to a pion lab. kinetic energy of 2 GeV using forward dispersion relation. A substantial number of data points have to be discarded to obtain a reasonable goodness of fit. Above 300 MeV the values of D/sub +or-/ obtained from the CERN phase shift analysis are strongly favoured compared with those from the Saclay analysis. The final results for the pion-nucleon coupling constant and s-wave scattering lengths are: 10/sup 3/f/sup 2 /=76.3+or-2.0, 10/sup 3/D/sub +/( mu )=-102.4+or-5.2, 10/sup 3/D/sub - /( mu )=104.8+or-5.4, 10/sup 3/(a/sub 1/-a/sub 3/)=270.6+or-11.3, 10 /sup 3/(a/sub 1/+2a/sub 3/)=3.1+or-8.0. The errors quoted take account of experimental uncertainties and also attempt to include systematic errors arising from the unphysical continuum and from the v...

  1. Dynamical generation of superconducting order of different symmetries in hexagonal lattices

    Science.gov (United States)

    Dehghani, Hossein; Mitra, Aditi

    2017-11-01

    The growth of superconducting order after an interaction quench in a hexagonal lattice is studied. The cases of both time-reversal (TR) preserving graphene, as well as the TR broken Haldane model, are explored. Spin singlet superconducting order is studied where the s ,d +i d , and d -i d wave orders are the irreducible representations of the hexagonal lattice. For small quenches, the d -wave order parameter grows the fastest, a result also expected when the system is in thermal equilibrium. For the TR symmetry preserving case, the growth rate of the two d -wave orders is identical, while the TR-broken case prefers one of the chiral d -wave orders over the other, leading to a TR broken topological superconductor. As the interaction quench becomes larger, a smooth crossover is found where eventually the growth rate of the s wave becomes the largest. Thus for large interaction quenches, the s wave is preferred over the d wave for both TR preserving and TR broken systems. This result is explained in terms of the high energy quasiparticles responsible for the dynamics as the interaction quench amplitude grows. The results are relevant for time-resolved measurements that can probe the symmetry of the superconducting fluctuations in a transient regime.

  2. Experiment for 3-component S-wave reflection survey. Part 3; Sanseibun S ha hanshaho no kiso jikken. 3

    Energy Technology Data Exchange (ETDEWEB)

    Kano, N.; Yamaguchi, K.; Yokota, T.; Kiguchi, T. [Geological Survey of Japan, Tsukuba (Japan)

    1996-10-01

    Anisotropy has been investigated using S-wave as a technique for detecting fractures. In this study, fundamental experiments were carried out with slightly changing the measuring conditions at a place where anisotropy was expected. This paper describes the fundamental data acquisition of anisotropy analysis using S-wave, and a part of the results. The experiments were conducted on the agricultural road in Yamadera district, Matsuyama-machi, Yamagata Prefecture. Two flat unpaved roads meeting at right angles were used as traverse lines. In this place, several reflection surfaces were certainly detected by P-wave, and anisotropy of S-wave was confirmed from the velocity of refracted wave of S-wave. Data were processed for individual traverse lines meeting at right angles. Firstly, signal sweeping, correlation, and vertical superposition were made. Six kinds of data were prepared, i.e., three-component receiving records of data at 0{degree} of generating direction and three-component receiving records of data at 90{degree} of generating direction. Records of T-component at 0{degree} and R-component at 90{degree} were used for processing of the seismic reflection method. These records would be considered to be data of SH-wave and SV-wave, respectively. 4 figs.

  3. Macroscopic quantum tunneling and quasiparticle-tunneling blockade effect in s-wave/d-wave hybrid junctions

    NARCIS (Netherlands)

    Kawabata, S.; Kawabata, S.; Golubov, Alexandre Avraamovitch; Ariando, A.; Verwijs, C.J.M.; Verwijs, C.J.M.; Hilgenkamp, Johannes W.M.; Kirtley, J.R.

    2007-01-01

    We have theoretically investigated macroscopic quantum tunneling (MQT) and the influence of nodal quasiparticles and zero energy bound states (ZESs) on MQT in s-wave/d-wave hybrid Josephson junctions. In contrast to d-wave/d-wave junctions, the low-energy quasiparticle dissipation resulting from

  4. Feasibility of using P- and S-wave Attenuation for Monitoring of Bacterial Clogging in Unconsolidated Sediments

    Science.gov (United States)

    Noh, D. H.

    2015-12-01

    Accumulation of bacterial biopolymers in porous media is known to decrease permeability by several orders of magnitude, referred to as bioclogging, thereby altering the hydraulic flow systems of porous media. Successful microbial bioclogging treatments require geophysical monitoring techniques to provide appropriate spatial and temporal information on bacterial growth and activities in the subsurface; such monitoring datasets can be used to evaluate the status of plugged reservoir sections and optimize re-treatment if the plug degrades. This study investigated the variations of P- and S-wave attenuation of porous media for monitoring in-situ accumulation of bacterial biopolymers in sediments. Column experiments, where Leuconostoc mesenterorides were stimulated to produce the insoluble polysaccharide biopolymer (referred to as dextran) in a sand pack, were performed while monitoring changes in permeability as well as P- and S-wave responses. P-wave responses at ultrasonic and sub-ultrasonic frequency ranges (i.e., hundreds of kHz and tens of kHz) and S-wave responses at several kHz were acquired using ultrasonic transducers and bender elements during accumulation of the biopolymer. The permeability of the sand pack was reduced by more than one order of magnitude while the insoluble biopolymer, dextran, produced by Leuconostoc mesenteroides occupied ~10% pore volume. The amplitude of the P-wave signals decreased at the both ultrasonic (hundreds of kHz) and sub-ultrasonic (tens of kHz) frequency ranges; and the spectral ratio calculations confirmed an increase in P-wave attenuation (1/QP) in the both frequency ranges. The amplitude of the S-wave signals significantly increased during the increase in S-wave velocity, possibly due to the increased shear stiffness of the medium. However, the spectral ratio calculation suggested an increase in S-wave attenuation (1/QS) in the several kHz band. The observed changes in permeability and P- and S-wave attenuation were

  5. Charge symmetry at the partonic level

    Energy Technology Data Exchange (ETDEWEB)

    Londergan, J. T.; Peng, J. C.; Thomas, A. W.

    2010-07-01

    This review article discusses the experimental and theoretical status of partonic charge symmetry. It is shown how the partonic content of various structure functions gets redefined when the assumption of charge symmetry is relaxed. We review various theoretical and phenomenological models for charge symmetry violation in parton distribution functions. We summarize the current experimental upper limits on charge symmetry violation in parton distributions. A series of experiments are presented, which might reveal partonic charge symmetry violation, or alternatively might lower the current upper limits on parton charge symmetry violation.

  6. A model of intrinsic symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Ge, Li [Research Center for Quantum Manipulation, Department of Physics, Fudan University, Shanghai 200433 (China); Li, Sheng [Department of Physics, Zhejiang Normal University, Zhejiang 310004 (China); George, Thomas F., E-mail: tfgeorge@umsl.edu [Office of the Chancellor and Center for Nanoscience, Department of Chemistry and Biochemistry, University of Missouri-St. Louis, St. Louis, MO 63121 (United States); Department of Physics and Astronomy, University of Missouri-St. Louis, St. Louis, MO 63121 (United States); Sun, Xin, E-mail: xin_sun@fudan.edu.cn [Research Center for Quantum Manipulation, Department of Physics, Fudan University, Shanghai 200433 (China)

    2013-11-01

    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.

  7. On four dimensional mirror symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Losev, A. [Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Nekrasov, N.; Shatashvili, S.

    2000-07-01

    A conjecture relating instanton calculus in four dimensional supersymmetric theories and the deformation theory of Lagrangian submanifolds in C{sup 2r} invariant under a (subgroup of) Sp(2r,Z) is formulated. This is a four dimensional counterpart of the mirror symmetry of topological strings (relating Gromov-Witten invariants and generalized variations of Hodge structure). (orig.)

  8. Baryon and chiral symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Gorsky, A. [Institute for Theoretical and Experimental Physics (ITEP), Moscow, Russia and Moscow Institute of Physics and Technology (MIPT), Dolgoprudny (Russian Federation); Krikun, A. [NORDITA, KTH Royal Institute of Technology and Stockholm University Stockholm, Sweden and Institute for Theoretical and Experimental Physics (ITEP), Moscow (Russian Federation)

    2014-07-23

    We briefly review the generalized Skyrmion model for the baryon recently suggested by us. It takes into account the tower of vector and axial mesons as well as the chiral symmetry breaking. The generalized Skyrmion model provides the qualitative explanation of the Ioffe’s formula for the baryon mass.

  9. Exploiting symmetry in protocol testing

    NARCIS (Netherlands)

    J.M.T. Romijn (Judi); J.G. Springintveld

    1999-01-01

    textabstractTest generation and execution are often hampered by the large state spaces of the systems involved. In automata (or transition system) based test algorithms, taking advantage of symmetry in the behavior of specification and implementation may substantially reduce the amount of tests. We

  10. Hidden local symmetry and beyond

    Science.gov (United States)

    Yamawaki, Koichi

    Gerry Brown was a godfather of our hidden local symmetry (HLS) for the vector meson from the birth of the theory throughout his life. The HLS is originated from very nature of the nonlinear realization of the symmetry G based on the manifold G/H, and thus is universal to any physics based on the nonlinear realization. Here, I focus on the Higgs Lagrangian of the Standard Model (SM), which is shown to be equivalent to the nonlinear sigma model based on G/H = SU(2)L × SU(2)R/SU(2)V with additional symmetry, the nonlinearly-realized scale symmetry. Then, the SM does have a dynamical gauge boson of the SU(2)V HLS, "SM ρ meson", in addition to the Higgs as a pseudo-dilaton as well as the NG bosons to be absorbed in to the W and Z. Based on the recent work done with Matsuzaki and Ohki, I discuss a novel possibility that the SM ρ meson acquires kinetic term by the SM dynamics itself, which then stabilizes the skyrmion dormant in the SM as a viable candidate for the dark matter, what we call "dark SM skyrmion (DSMS)".

  11. The Symmetry of Natural Laws.

    Science.gov (United States)

    Brown, Laurie M.

    This document is a monograph intended for advanced undergraduate students, or beginning graduate students, who have some knowledge of modern physics as well as classical physics, including the elementary quantum mechanical treatment of the hydrogen atom and angular momentum. The first chapter introduces symmetry and relates it to the mathematical…

  12. Experimental tests of fundamental symmetries

    NARCIS (Netherlands)

    Jungmann, K. P.

    2014-01-01

    Ongoing experiments and projects to test our understanding of fundamental inter- actions and symmetries in nature have progressed significantly in the past few years. At high energies the long searched for Higgs boson has been found; tests of gravity for antimatter have come closer to reality;

  13. Lifshitz symmetries and nonrelativistic holography

    NARCIS (Netherlands)

    Sybesma, Z.W.

    2017-01-01

    In this dissertation we cover topics within the main themes of Lifshitz symmetries and nonrelativistic holography. Nonrelativistic theories are typically less constrained than relativistic ones, which makes them often more cumbersome to work with. Via holography one can have acces to domains of a

  14. Symmetry in labeled transition systems

    NARCIS (Netherlands)

    I.A. van Langevelde

    2003-01-01

    textabstractSymmetry is defined for labeled transition systems, and it is shown how symmetrical systems can be symmetrically decomposed into components. The central question is under what conditions one such component may represent the whole system, in the sense that one symmetrical system is

  15. Symmetry structure and phase transitions

    Indian Academy of Sciences (India)

    ... symmetry structure at finite density and temperature in the presence of external magnetic field and gravity, a situation relevant in the early Universe and in the core of compact stars. We then investigate the dynamical evolution of phase transition in the expanding early Universe and possible formation of quark nuggets and ...

  16. Strong coupling electroweak symmetry breaking

    Energy Technology Data Exchange (ETDEWEB)

    Barklow, T.L. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Burdman, G. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Physics; Chivukula, R.S. [Boston Univ., MA (United States). Dept. of Physics

    1997-04-01

    The authors review models of electroweak symmetry breaking due to new strong interactions at the TeV energy scale and discuss the prospects for their experimental tests. They emphasize the direct observation of the new interactions through high-energy scattering of vector bosons. They also discuss indirect probes of the new interactions and exotic particles predicted by specific theoretical models.

  17. Bound-state energy of the three-dimensional Ising model in the broken-symmetry phase: suppressed finite-size corrections.

    Science.gov (United States)

    Nishiyama, Yoshihiro

    2008-05-01

    The low-lying spectrum of the three-dimensional Ising model is investigated numerically; we made use of an equivalence between the excitation gap and the reciprocal correlation length. In the broken-symmetry phase, the magnetic excitations are attractive, forming a bound state with an excitation gap m_{2} (mass-gap ratio as m_{2}/m_{1}=1.84(3) .

  18. Dynamics of nanoparticules detected at 1 AU by S/WAVES onboard STEREO spacecraft

    Science.gov (United States)

    Belheouane, Soraya; Issautier, Karine; Meyer-Vernet, Nicole; Le Chat, Gaétan; Czechowski, Andrzej; Zaslavsky, Arnaud; Zouganelis, Yannis; Mann, Ingrid

    In order to interpret in detail the S/WAVES data on the interplanetary nanodust discovered by STEREO at 1 AU [Meyer-Vernet et al., 2009], we study the dynamics of nanoparticles in the inner interplanetary medium as well as the distribution of their velocities and directions of arrival, with a model based on [Czechowski and Mann, 2012]. We deduce the charges released by their impacts on the STEREO spacecraft at 1 AU and their dependence on the position of the spacecraft on their orbits. The model studies nanoparticles of size equal or smaller than about 70 nm, assumed to be created via collisional fragmentation of dust grains of larger size moving on keplerian orbits, and sublimation of dust, meteoroids and comets. The nanoparticles are released near the Sun with initial velocities close to keplerian, and mainly subjected to the Lorentz force calculated with a simple solar wind model. A part of the nanoparticles is accelerated to high speeds of the order of 300 km/s, thereby providing impact charges between 10(-14) and 10(-11) Cb [Belheouane, 2014] which enable them to be detected by S/WAVES, whereas another part is trapped within about 0.2 AU from the Sun. We discuss how the fluxes and direction of arrival at 1 AU are expected to change in function of the solar cycle. These results enable us to interpret in detail the STEREO/WAVES observations [Zaslavsky et al., 2012]; [Pantellini et al., 2013]; [Le Chat et al., 2013]. Belheouane, S. (2014). Nanoparticules dans le vent solaire, observations spatiales et theorie. PhD thesis, Pierre and Marie Curie University UPMC. Czechowski, A. and Mann, I. (2012). Nanodust Dynamics in Interplanetary Space, chapter Nanodust Dynamics in Interplanetary Space. Springer Berlin Heidelberg. Le Chat, G., Zaslavsky, A., Meyer-Vernet, N., Issautier, K., Belheouane, S., Pantellini, F., Maksimovic, M., Zouganelis, I., Bale, S., and Kasper, J. (2013). Interplanetary Nanodust Detection by the Solar Terrestrial Relations Observatory/WAVES Low

  19. All Majorana Models with Translation Symmetry are Supersymmetric

    CERN Document Server

    Hsieh, Timothy H; Grover, Tarun

    2016-01-01

    We establish results similar to Kramers and Lieb-Schultz-Mattis theorems but involving only translation symmetry and for Majorana modes. In particular, we show that all states are at least doubly degenerate in any one and two dimensional array of Majorana modes with translation symmetry, periodic boundary conditions, and an odd number of modes per unit cell. Moreover, we show that all such systems have an underlying N=2 supersymmetry and explicitly construct the generator of the supersymmetry. Furthermore, we show that there cannot be a unique gapped ground state in such one dimensional systems with anti-periodic boundary conditions. These general results are fundamentally a consequence of the fact that translations for Majorana modes are represented projectively, which in turn stems from the anomalous nature of a single Majorana mode.

  20. Topological edge modes with PT symmetry in a quasiperiodic structure

    Science.gov (United States)

    Rivolta, Nicolas X. A.; Benisty, Henri; Maes, Bjorn

    2017-08-01

    We investigate topological features of a one-dimensional photonic quasicrystal within the context of PT symmetry. Via the scattering characteristics, we analyze various properties of a particular mirrored structure, which supports topological edge modes in its band gaps. These interface modes display a nontrivial dependence on the quasiperiodic geometry, even in a passive system. Subsequently, the tailored addition of gain and loss generates curious PT -like features. For example, the quasicrystal high density of modes leads to complicated mode-merging behaviors between edge and band modes, such as the symmetry recovery phenomenon. Furthermore, anisotropic transmission resonances (connected with unidirectional invisibility) are also present, but they display richer patterns in comparison to previously studied periodic structures. Additionally, we examine lasing effects in detail, with numerics and a simple Fabry-Pérot model. The large variety of mode-merging behaviors opens the way to laser resonance engineering.

  1. Spontaneous formation and stability of small GaP fullerenes

    OpenAIRE

    Tozzini, V.; Buda, F.; Fasolino, A.

    2000-01-01

    We report the spontaneous formation of a GaP fullerene cage in ab-initio Molecular Dynamics simulations starting from a bulk fragment. A systematic study of the geometric and electronic properties of neutral and ionized GaP clusters suggests the stability of hetero-fullerenes formed by a compound with zincblend bulk structure. We find that GaP fullerenes up to 28 atoms have high symmetry, closed electronic shells, large HOMO-LUMO energy gaps and do not dissociate when ionized. We compare our ...

  2. Symmetry properties of the nodal superconductor PrOs4Sb12

    Science.gov (United States)

    Abu Alrub, T. R.; Curnoe, S. H.

    2007-08-01

    We present a theoretical study of the superconducting gap function in PrOs4Sb12 using a symmetry-based approach. A three-component order parameter in the triplet channel best describes superconductivity. The gap function is nondegenerate and the lower branch has four cusp nodes at unusual points of the Fermi surface, which lead to power law behaviors in the density of states, specific heat, and nuclear spin relaxation rate.

  3. The Gap Within the Gap

    Directory of Open Access Journals (Sweden)

    Katherine Michelmore

    2017-02-01

    Full Text Available Gaps in educational achievement between high- and low-income children are growing. Administrative data sets maintained by states and districts lack information about income but do indicate whether a student is eligible for subsidized school meals. We leverage the longitudinal structure of these data sets to develop a new measure of economic disadvantage. Half of eighth graders in Michigan are eligible for a subsidized meal, but just 14% have been eligible for subsidized meals in every grade since kindergarten. These children score 0.94 standard deviations below those who are never eligible for meal subsidies and 0.23 below those who are occasionally eligible. There is a negative, linear relationship between grades spent in economic disadvantage and eighth-grade test scores. This is not an exposure effect; the relationship is almost identical in third-grade, before children have been exposed to varying years of economic disadvantage. Survey data show that the number of years that a child will spend eligible for subsidized lunch is negatively correlated with her or his current household income. Years eligible for subsidized meals can therefore be used as a reasonable proxy for income. Our proposed measure can be used to estimate heterogeneous effects in program evaluations, to improve value-added calculations, and to better target resources.

  4. Involution symmetries and the PMNS matrix

    Indian Academy of Sciences (India)

    2017-10-09

    Oct 9, 2017 ... C S Lam has suggested that the PMNS matrix (or at least some of its elements) can be predicted by embedding the residual symmetry of the leptonic mass terms into a bigger symmetry. We analyse the possibility that the residual symmetries consist of involution generators only and explore how Lam's idea ...

  5. P-wave and S-wave traveltime residuals in Caledonian and adjacent units of Northern Europe and Greenland

    Science.gov (United States)

    Hejrani, Babak; Balling, Niels; Holm Jacobsen, Bo; Kind, Rainer; Tilmann, Frederik; England, Richard; Bom Nielsen, Søren

    2014-05-01

    This work combines P-wave and S-wave travel time residuals from in total 477 temporary and 56 permanent stations deployed across Caledonian and adjacent units in Northern Europe and Greenland (Tor, Gregersen et al. 2002; SVEKALAPKO, Sandoval et al., 2003; CALAS, Medhus et al, 2012a; MAGNUS, Weidle et al. 2010; SCANLIPS south, England & Ebbing 2012; SCANLIPS north, Hejrani et al. 2012; JULS Hejrani et al. 2013; plus permanent stations in the region). We picked data from 2002 to 2012 (1221 events) using a cross correlation technique on all waveforms recorded for each event. In this way we achieve maximum consistency of relative residuals over the whole region (Medhus et al. 2012b). On the European side 18362 P-wave travel time residuals was delivered. In East Greenland 1735 P-wave residuals were recovered at the Central Fjord array (13 stations) and 2294 residuals from the sparse GLISN-array (23 stations). Likewise, we picked a total of 6034 residuals of the SV phase (For the Tor and SVEKALAPKO projects we used data from Amaru et al. 2008). Relative residuals within the region are mainly due to sub-crustal uppermost mantle velocity anomalies. A dominant subvertical boundary was detected by Medhus et al. (2012), running along the Tornquist zone, east of the Oslo Graben and crossing under high topography of the southern Scandes. We delineated this boundary in more detail, tracking it towards the Atlantic margin north of Trondheim. Further north (Scanlips north), a similar subvertical upper mantle boundary seems to be present close to the coast, coinciding with the edge of the stretched crust. The North German Caledonides were probed by the new JULS (JUtland Lower Saxony) profile which closes the gap between Tor and CALAS arrays. Mantle structure found by the Tor project was confirmed, and modelling was extended to the eastern edge of the North Sea. References: Amaru, M. L., Spakman, W., Villaseñor, A., Sandoval, S., Kissling, E., 2008, A new absolute arrival time data

  6. The Construction of Mirror Symmetry

    CERN Document Server

    Schimmrigk, R

    1992-01-01

    The construction of mirror symmetry in the heterotic string is reviewed in the context of Calabi-Yau and Landau-Ginzburg compactifications. This framework has the virtue of providing a large subspace of the configuration space of the heterotic string, probing its structure far beyond the present reaches of solvable models. The construction proceeds in two stages: First all singularities/catastrophes which lead to ground states of the heterotic string are found. It is then shown that not all ground states described in this way are independent but that certain classes of these LG/CY string vacua can be related to other, simpler, theories via a process involving fractional transformations of the order parameters as well as orbifolding. This construction has far reaching consequences. Firstly it allows for a systematic identification of mirror pairs that appear abundantly in this class of string vacua, thereby showing that the emerging mirror symmetry is not accidental. This is important because models with mirro...

  7. Tensionless strings from worldsheet symmetries

    Energy Technology Data Exchange (ETDEWEB)

    Bagchi, Arjun [Center for Theoretical Physics, Massachusetts Institute of Technology,77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Chakrabortty, Shankhadeep; Parekh, Pulastya [Indian Institute of Science Education and Research,Dr Homi Bhabha Road, Pashan, Pune 411008, INDIA (India); Van Swinderen Institute for Particle Physics and Gravity, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands)

    2016-01-27

    We revisit the construction of the tensionless limit of closed bosonic string theory in the covariant formulation in the light of Galilean conformal symmetry that rises as the residual gauge symmetry on the tensionless worldsheet. We relate the analysis of the fundamentally tensionless theory to the tensionless limit that is viewed as a contraction of worldsheet coordinates. Analysis of the quantum regime uncovers interesting physics. The degrees of freedom that appear in the tensionless string are fundamentally different from the usual string states. Through a Bogoliubov transformation on the worldsheet, we link the tensionless vacuum to the usual tensile vacuum. As an application, we show that our analysis can be used to understand physics of strings at very high temperatures and propose that these new degrees of freedom are naturally connected with the long-string picture of the Hagedorn phase of free string theory. We also show that tensionless closed strings behave like open strings.

  8. Symmetry structure and phase transitions

    Indian Academy of Sciences (India)

    2 µ2(σ2 +π2) + 1. 4λ(σ2 +π2)2. (2). For µ2. 0 chiral symmetry is spontaneously broken. Theσ field can be used to represent the quark condensate, the order parameter for chiral phase transition and the pions are the. Goldstone bosons. At the tree level the sigma, pion and the quark masses are given by m2 σ =3λσ2 cl µ2; m2.

  9. 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.

  10. Symmetry Decomposition of Chaotic Dynamics

    CERN Document Server

    Cvitanovic, P; Cvitanovi\\'c, Predrag; Eckhardt, Bruno

    1993-01-01

    Discrete symmetries of dynamical flows give rise to relations between periodic orbits, reduce the dynamics to a fundamental domain, and lead to factorizations of zeta functions. These factorizations in turn reduce the labor and improve the convergence of cycle expansions for classical and quantum spectra associated with the flow. In this paper the general formalism is developed, with the $N$-disk pinball model used as a concrete example and a series of physically interesting cases worked out in detail.

  11. Determination of the s-wave pion-nucleon threshold scattering parameters from the results of experiments on pionic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Oades, G.C. [Institute of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Rasche, G. [Institut fuer Theoretische Physik der Universitaet, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Woolcock, W.S. [Department of Theoretical Physics, IAS, Australian National University, Canberra, ACT 0200 (Australia); Matsinos, E. [Varian Medical Systems Imaging Laboratory GmbH, Taefernstrasse 7, CH-5405 Baden-Daettwil (Switzerland)], E-mail: evangelos.matsinos@varian.com; Gashi, A. [Mediscope AG, Alfred Escher-Str. 27, CH-8002 Zuerich (Switzerland)

    2007-10-01

    We give the conversion equations which lead from experimental values of the 3p{yields}1s transition energy in pionic hydrogen and the total width of the 1s level to values of the s-wave threshold scattering parameters for the processes {pi}{sup -}p{yields}{pi}{sup -}p and {pi}{sup -}p{yields}{pi}{sup 0}n respectively. Using a three-channel potential model, we then calculate the electromagnetic corrections to these quantities, which remove the effects of the Coulomb interaction, the external mass differences and the presence of the {gamma}n channel. We give the s-wave scattering parameters obtained from the present experimental data and these electromagnetic corrections. Finally we discuss the implications for isospin invariance.

  12. Detecting P and S-wave of Mt. Rinjani seismic based on a locally stationary autoregressive (LSAR) model

    Science.gov (United States)

    Nurhaida, Subanar, Abdurakhman, Abadi, Agus Maman

    2017-08-01

    Seismic data is usually modelled using autoregressive processes. The aim of this paper is to find the arrival times of the seismic waves of Mt. Rinjani in Indonesia. Kitagawa algorithm's is used to detect the seismic P and S-wave. Householder transformation used in the algorithm made it effectively finding the number of change points and parameters of the autoregressive models. The results show that the use of Box-Cox transformation on the variable selection level makes the algorithm works well in detecting the change points. Furthermore, when the basic span of the subinterval is set 200 seconds and the maximum AR order is 20, there are 8 change points which occur at 1601, 2001, 7401, 7601,7801, 8001, 8201 and 9601. Finally, The P and S-wave arrival times are detected at time 1671 and 2045 respectively using a precise detection algorithm.

  13. Boundary conformal field theory and symmetry-protected topological phases in 2 +1 dimensions

    Science.gov (United States)

    Han, Bo; Tiwari, Apoorv; Hsieh, Chang-Tse; Ryu, Shinsei

    2017-09-01

    We propose a diagnostic tool for detecting nontrivial symmetry-protected topological (SPT) phases protected by a symmetry group G in 2 +1 dimensions. Our method is based on directly studying the 1 +1 -dimensional anomalous edge conformal field theory (CFT) of SPT phases. We claim that if the CFT is the edge theory of an SPT phase, then there must be an obstruction to cutting it open. This obstruction manifests as the in-existence of boundary states in the CFT that preserves both the conformal symmetry and the global symmetry G . We discuss the relation between edgeability, i.e., the ability to find a consistent boundary state, and gappability, i.e., the ability to gap out a CFT, in the presence of G . We study several cases including time-reversal symmetric topological insulators, ZN symmetric bosonic SPT phases, and Z2×Z2 symmetric topological superconductors.

  14. Two-Dimensional Dirac Fermions Protected by Space-Time Inversion Symmetry in Black Phosphorus

    Science.gov (United States)

    Kim, Jimin; Baik, Seung Su; Jung, Sung Won; Sohn, Yeongsup; Ryu, Sae Hee; Choi, Hyoung Joon; Yang, Bohm-Jung; Kim, Keun Su

    2017-12-01

    We report the realization of novel symmetry-protected Dirac fermions in a surface-doped two-dimensional (2D) semiconductor, black phosphorus. The widely tunable band gap of black phosphorus by the surface Stark effect is employed to achieve a surprisingly large band inversion up to ˜0.6 eV . High-resolution angle-resolved photoemission spectra directly reveal the pair creation of Dirac points and their movement along the axis of the glide-mirror symmetry. Unlike graphene, the Dirac point of black phosphorus is stable, as protected by space-time inversion symmetry, even in the presence of spin-orbit coupling. Our results establish black phosphorus in the inverted regime as a simple model system of 2D symmetry-protected (topological) Dirac semimetals, offering an unprecedented opportunity for the discovery of 2D Weyl semimetals.

  15. Generation of High-Frequency P and S Wave Energy by Rock Fracture During a Buried Explosion

    Science.gov (United States)

    2015-07-20

    speed digital cameras, and monitored the resultant seismic waves using a laser vibrometer (as an ultra-high-frequency seismometer). We originally... laser vibrometers to record particle velocities in the resultant P and S waves. Since no mechanical data was available for candy- glass, we measured...plates photographing them using high-speed digital cameras, and monitoring the resultant seismic waves using laser vibrometers (as an array of

  16. Upper mantle seismic structure beneath southwest Africa from finite-frequency P- and S-wave tomography

    DEFF Research Database (Denmark)

    Soliman, Mohammad Youssof Ahmad; Yuan, Xiaohui; Tilmann, Frederik

    2015-01-01

    We present a 3D high-resolution seismic model of the southwestern Africa region from teleseismic tomographic inversion of the P- and S- wave data recorded by the amphibious WALPASS network. We used 40 temporary stations in southwestern Africa with records for a period of 2 years (the OBS operated...... inferred from teleseismic shear waves indicate a predominant NE-SW ori- entation for most of the land stations. Current results indicate no evidence for a consistent signature of fossil plume....

  17. Tunable symmetry breaking and helical edge transport in a graphene quantum spin Hall state.

    Science.gov (United States)

    Young, A F; Sanchez-Yamagishi, J D; Hunt, B; Choi, S H; Watanabe, K; Taniguchi, T; Ashoori, R C; Jarillo-Herrero, P

    2014-01-23

    Low-dimensional electronic systems have traditionally been obtained by electrostatically confining electrons, either in heterostructures or in intrinsically nanoscale materials such as single molecules, nanowires and graphene. Recently, a new method has emerged with the recognition that symmetry-protected topological (SPT) phases, which occur in systems with an energy gap to quasiparticle excitations (such as insulators or superconductors), can host robust surface states that remain gapless as long as the relevant global symmetry remains unbroken. The nature of the charge carriers in SPT surface states is intimately tied to the symmetry of the bulk, resulting in one- and two-dimensional electronic systems with novel properties. For example, time reversal symmetry endows the massless charge carriers on the surface of a three-dimensional topological insulator with helicity, fixing the orientation of their spin relative to their momentum. Weakly breaking this symmetry generates a gap on the surface, resulting in charge carriers with finite effective mass and exotic spin textures. Analogous manipulations have yet to be demonstrated in two-dimensional topological insulators, where the primary example of a SPT phase is the quantum spin Hall state. Here we demonstrate experimentally that charge-neutral monolayer graphene has a quantum spin Hall state when it is subjected to a very large magnetic field angled with respect to the graphene plane. In contrast to time-reversal-symmetric systems, this state is protected by a symmetry of planar spin rotations that emerges as electron spins in a half-filled Landau level are polarized by the large magnetic field. The properties of the resulting helical edge states can be modulated by balancing the applied field against an intrinsic antiferromagnetic instability, which tends to spontaneously break the spin-rotation symmetry. In the resulting canted antiferromagnetic state, we observe transport signatures of gapped edge states

  18. Chiral dynamics, S-wave contributions and angular analysis in D → ππl anti ν

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Yu-Ji; Wang, Wei; Zhao, Shuai [Shanghai Jiao-Tong University, INPAC, Shanghai Key Laboratory for Particle Physics and Cosmology, Department of Physics and Astronomy, Shanghai (China)

    2017-07-15

    We present a theoretical analysis of the D{sup -} → π{sup +}π{sup -}l anti ν and anti D{sup 0} → π{sup +}π{sup 0}l anti ν decays. We construct a general angular distribution which can include arbitrary partial waves of ππ. Retaining the S-wave and P-wave contributions we study the branching ratios, forward-backward asymmetries and a few other observables. The P-wave contribution is dominated by ρ{sup 0} resonance, and the S-wave contribution is analyzed using the unitarized chiral perturbation theory. The obtained branching fraction for D → ρlν, at the order 10{sup -3}, is consistent with the available experimental data. The S-wave contribution has a branching ratio at the order of 10{sup -4}, and this prediction can be tested by experiments like BESIII and LHCb. Future measurements can also be used to examine the π-π scattering phase shift. (orig.)

  19. Matrix product operators for symmetry-protected topological phases: Gauging and edge theories

    Science.gov (United States)

    Williamson, Dominic J.; Bultinck, Nick; Mariën, Michael; Şahinoǧlu, Mehmet B.; Haegeman, Jutho; Verstraete, Frank

    2016-11-01

    Projected entangled pair states (PEPS) provide a natural ansatz for the ground states of gapped, local Hamiltonians in which global characteristics of a quantum state are encoded in properties of local tensors. We develop a framework to describe onsite symmetries, as occurring in systems exhibiting symmetry-protected topological (SPT) quantum order, in terms of virtual symmetries of the local tensors expressed as a set of matrix product operators (MPOs) labeled by distinct group elements. These MPOs describe the possibly anomalous symmetry of the edge theory, whose local degrees of freedom are concretely identified in a PEPS. A classification of SPT phases is obtained by studying the obstructions to continuously deforming one set of MPOs into another, recovering the results derived for fixed-point models [Chen et al., Phys. Rev. B 87, 155114 (2013), 10.1103/PhysRevB.87.155114]. Our formalism accommodates perturbations away from fixed-point models, opening the possibility of studying phase transitions between different SPT phases. We also demonstrate that applying the recently developed quantum state gauging procedure to a SPT PEPS yields a PEPS with topological order determined by the initial symmetry MPOs. The MPO framework thus unifies the different approaches to classifying SPT phases, via fixed-point models, boundary anomalies, or gauging the symmetry, into the single problem of classifying inequivalent sets of matrix product operator symmetries that are defined purely in terms of a PEPS.

  20. Bulk superconducting gap of V{sub 3}Si studied by low-energy ultrahigh-resolution photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sato, T., E-mail: t-sato@arpes.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Souma, S. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Nakayama, K. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Sugawara, K. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Toyota, N. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Takahashi, T. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2016-04-15

    Highlights: • We report ultrahigh-resolution photoemission spectroscopy of A15 compound V{sub 3}Si. • We found a sharp quasiparticle peak due to superconducting-gap opening. • The surface metallic component is negligibly small in the bulk-sensitive measurement. • We show that V{sub 3}Si is a single-gap s-wave superconductor. - Abstract: We have performed low-energy ultrahigh-resolution photoemission spectroscopy (PES) of A15 compound V{sub 3}Si with a xenon-plasma discharge lamp to elucidate the bulk superconducting gap. Below the superconducting transition temperature (T{sub c} = 15.9 K), we found a sharp quasiparticle peak at the Fermi level in the PES spectrum. The gap spectrum is well fitted by a single s-wave superconducting-gap function together with a dip structure at ∼30 meV suggestive of a strong electron-phonon coupling. The anomalous in-gap state previously observed in the PES measurement with high-energy photons is absent or negligibly small in the present bulk-sensitive measurement. The present PES result shows that V{sub 3}Si is a single-gap s-wave superconductor.

  1. Estimation of earthquake source parameters in the Kachchh seismic zone, Gujarat, India, using three component S-wave spectra

    Science.gov (United States)

    Nagamani, Durgada; Mandal, Prantik

    2017-07-01

    Earthquake source parameters and crustal Q0 values for the 138 selected local events of (Mw{:}2.5{-}4.4) the 2001 Bhuj earthquake sequence have been computed through inversion modelling of S-waves from three-component broadband seismometer data. SEISAN software has been used to locate the identified local earthquakes, which were recorded at least three or more stations of the Kachchh seismological network. Three component spectra of S-wave are being inverted by using the Levenberg-Marquardt non-linear inversion technique, wherein the inversion scheme is formulated based on ω 2 source model. SAC Software (seismic analysis code) is being utilized for calculating three-component displacement and velocity spectra of S-wave. The displacement spectra are used for estimating corner frequency (in Hz) and long period spectral level (in nm-s). These two parameters play a key role in estimating earthquake source parameters. The crustal {Q}0 values have been computed simultaneously for each component of three-component broadband seismograph. The estimated seismic moment (M0) and source radius ( r) using S-wave spectra range from 7.03E+12 to 5.36E+15 N-m and 178.56 to 565.21 m, respectively. The corner frequencies for S-wave vary from 3.025 to 7.425 Hz. We also estimated the radiated energy (ES) using velocity spectra, which is varying from 2.76E+06 to 4.07E+11 Joules. The estimated apparent stress drop and static stress drop values range from 0.01 to 2.56 and 0.53 to 36.79 MPa, respectively. Our study also reveals that estimated Q0 values vary from 119.0 to 7229.5, with an average Q0 value of 701. Another important parameter, by which the earthquake rupture process can be recognized, is Zuniga parameter. It suggests that most of the Kachchh events follow the frictional overshoot model. Our estimated static stress drop values are higher than the apparent stress drop values. And the stress drop values are quite larger for intraplate earthquakes than the interplate earthquakes.

  2. Symmetry breaking of zero energy landau level in monolayer graphene

    Science.gov (United States)

    Zhao, Yue; Cadden-Zimansky, Paul; Ghahari, Fereshte; Kim, Philip

    2011-03-01

    We experimentally study the nature of the symmetry breaking of the zero energy landau level (LL) in monolayer graphene using Corbino geometry and Hall bar geometry devices. At high magnetic fields, in the absence of the edge state channel connection in Corbino devices, we observe a gap opening in ν = 0 QH state whose gap is independent of in-plane magnetic field. In Hall-bar geometry devices where edge state connection is allowed, we observe similar QH Insulator behavior independent of the in-plane magnetic field, indicating that the observed insulating behavior at the charge neutrality point of monolayer graphene at high magnetic field is originated from the degeneracy lifting of the zero LL via the valley pseudospin polarization rather spin polarization.

  3. Universal Quantum Computation with Gapped Boundaries

    Science.gov (United States)

    Cong, Iris; Cheng, Meng; Wang, Zhenghan

    2017-10-01

    This Letter discusses topological quantum computation with gapped boundaries of two-dimensional topological phases. Systematic methods are presented to encode quantum information topologically using gapped boundaries, and to perform topologically protected operations on this encoding. In particular, we introduce a new and general computational primitive of topological charge measurement and present a symmetry-protected implementation of this primitive. Throughout the Letter, a concrete physical example, the Z3 toric code [D (Z3)], is discussed. For this example, we have a qutrit encoding and an abstract universal gate set. Physically, gapped boundaries of D (Z3) can be realized in bilayer fractional quantum Hall 1 /3 systems. If a practical implementation is found for the required topological charge measurement, these boundaries will give rise to a direct physical realization of a universal quantum computer based on a purely Abelian topological phase.

  4. Hidden symmetries of deformed oscillators

    Directory of Open Access Journals (Sweden)

    Sergey Krivonos

    2017-11-01

    Full Text Available We associate with each simple Lie algebra a system of second-order differential equations invariant under a non-compact real form of the corresponding Lie group. In the limit of a contraction to a Schrödinger algebra, these equations reduce to a system of ordinary harmonic oscillators. We provide two clarifying examples of such deformed oscillators: one system invariant under SO(2,3 transformations, and another system featuring G2(2 symmetry. The construction of invariant actions requires adding semi-dynamical degrees of freedom; we illustrate the algorithm with the two examples mentioned.

  5. Crossing symmetry in Alpha space

    CERN Document Server

    CERN. Geneva

    2017-01-01

    The conformal bootstrap program aims to catalog all conformal field theories (second-order phase transitions) in D dimensions. Despite its ambitious scope much progress has been made over the past decade, e.g. in computing critical exponents for the 3D O(N) models to high precision. At this stage, analytic methods to explore the CFT landscape are not as well developed. In this talk I will describe a new mathematical framework for the bootstrap known as "alpha space", which reduces crossing symmetry to a set of integral equations. Based on arXiv:1702.08471 (with Balt van Rees) and arXiv:1703.08159.

  6. History of electroweak symmetry breaking

    CERN Document Server

    Kibble, T W B

    2015-01-01

    In this talk, I recall the history of the development of the unified electroweak theory, incorporating the symmetry-breaking Higgs mechanism, as I saw it from my standpoint as a member of Abdus Salam's group at Imperial College. I start by describing the state of physics in the years after the Second World War, explain how the goal of a unified gauge theory of weak and electromagnetic interactions emerged, the obstacles encountered, in particular the Goldstone theorem, and how they were overcome, followed by a brief account of more recent history, culminating in the historic discovery of the Higgs boson in 2012.

  7. Why we still don`t know the symmetry of the order parameter in high temperature superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Klemm, R.A. [Argonne National Lab., IL (United States). Materials Science Div.

    1997-03-01

    One of the most elusive topics in the study of high temperature superconductors (HTCS) is the orbital symmetry of the superconducting order parameter {Delta}. The low temperature T behavior observed in many experiments suggests that {Delta} might exhibit line nodes, as expected for d{sub x}{sub {minus}y}2 orbital symmetry. However, such behavior also arises from intrinsic proximity coupling and surface states, etc. The paramagnetic Meissner effect, once cited as indirect evidence for a d-wave {Delta}, was recently observed in Nb. Some phase-sensitive Josephson junction experiments gave strong evidence for a substantial isotropic, or s-wave, component to {Delta}, whereas others supported the above d-wave form. However, such experiments are intrinsically unreliable in experimental geometries with sample corners, or with meandering grain boundary junctions and stoichiometry inhomogeneities. Finally, the pseudogap observed recently in underdoped HTCS could arise from a charge-density wave.

  8. Interocular symmetry in myopic anisometropia.

    Science.gov (United States)

    Vincent, Stephen J; Collins, Michael J; Read, Scott A; Carney, Leo G; Yap, Maurice K H

    2011-12-01

    To investigate the interocular symmetry of optical, biometric, and biomechanical characteristics between the fellow eyes of myopic anisometropes. Thirty-four young, healthy myopic anisometropic adults (≥ 1 D spherical equivalent difference between eyes) without amblyopia or strabismus were recruited. A range of biometric and optical parameters were measured in both eyes of each subject including axial length, ocular aberrations, intraocular pressure, corneal topography, and biomechanics. Ocular sighting dominance was also measured. Mean absolute spherical equivalent anisometropia was 1.70 ± 0.74 D, and there was a strong correlation between the degree of anisometropia and the interocular difference in axial length (r = 0.81, p anisometropia exceeded 1.75 D, the more myopic eye was more likely to be the dominant sighting eye than for lower levels of anisometropia (p = 0.002). Subjects with greater levels of anisometropia (>1.75 D) also showed high levels of correlation between the dominant and non-dominant eyes in their biometric, biomechanical, and optical characteristics. Although significantly different in axial length, anisometropic eyes display a high degree of interocular symmetry for a range of anterior eye biometrics and optical parameters. For higher levels of anisometropia, the more myopic eye tends to be the dominant sighting eye.

  9. Discrete symmetries with neutral mesons

    Science.gov (United States)

    Bernabéu, José

    2018-01-01

    Symmetries, and Symmetry Breakings, in the Laws of Physics play a crucial role in Fundamental Science. Parity and Charge Conjugation Violations prompted the consideration of Chiral Fields in the construction of the Standard Model, whereas CP-Violation needed at least three families of Quarks leading to Flavour Physics. In this Lecture I discuss the Conceptual Basis and the present experimental results for a Direct Evidence of Separate Reversal-in-Time T, CP and CPT Genuine Asymmetries in Decaying Particles like Neutral Meson Transitions, using Quantum Entanglement and the Decay as a Filtering Measurement. The eight transitions associated to the Flavour-CP eigenstate decay products of entangled neutral mesons have demonstrated with impressive significance a separate evidence of TRV and CPV in Bd-physics, whereas a CPTV asymmetry shows a 2σ effect interpreted as an upper limit. Novel CPTV observables are discussed for K physics at KLOE-2, including the difference between the semileptonic asymmetries from KL and KS, the ratios of double decay rate Intensities to Flavour-CP eigenstate decay products and the ω-effect. Their observation would lead to a change of paradigm beyond Quantum Field Theory, however there is nothing in Quantum Mechanics forbidding CPTV.

  10. Gauge Invariance and Broken Symmetries in Anyon Superfluids

    Science.gov (United States)

    Boyanovsky, Daniel

    We review aspects of broken symmetry and the nature of long range order in theories of anyons starting with bosons with a statistical interaction. We introduce a novel gauge invariant quantization scheme that allows the identification of local and gauge invariant order parameters. The connection between spin and statistics is reviewed and the consequences of broken symmetries in the anyon representation are discussed. An anyon gas is studied in the Bogoliubov approximation, it is determined that the ground state is a condensate of charge-flux composites with “quasi-long-range order” at zero temperature, a “weak” gap in the spectrum and finite helicity modulus. The system is disordered at nonzero temperatures. The disorder is not caused by Goldstone bosons but by the strong infrared behavior arising from the Coulomb interaction induced by the long-range statistical interaction. The properties of topological vortices in nonrelativistic and in relativistic Landau-Ginzburg theories are studied in detail. We study the physics of the mean-field ansatz and quasi-long range order in a simple exactly soluble relativistic model. This model exhibits a novel phenomenon of charge redistribution to the boundaries and restoration of translational invariance in the infinite volume limit. It also illuminates the physics of quasi-long-range order with a gap in the spectrum, statistical charge polarization by external magnetic fields and the role of “large” gauge transformations.

  11. Topology and symmetry of surface Majorana arcs in cyclic superconductors

    Science.gov (United States)

    Mizushima, Takeshi; Nitta, Muneto

    2018-01-01

    We study the topology and symmetry of surface Majorana arcs in superconductors with nonunitary "cyclic" pairing. Cyclic p -wave pairing may be realized in a cubic or tetrahedral crystal, while it is a candidate for the interior P32 superfluids of neutron stars. The cyclic state is an admixture of full gap and nodal gap with eight Weyl points and the low-energy physics is governed by itinerant Majorana fermions. We here show the evolution of surface states from Majorana cone to Majorana arcs under rotation of surface orientation. The Majorana cone is protected solely by an accidental spin rotation symmetry and fragile against spin-orbit coupling, while the arcs are attributed to two topological invariants: the first Chern number and one-dimensional winding number. Lastly, we discuss how topologically protected surface states inherent to the nonunitary cyclic pairing can be captured from surface probes in candidate compounds, such as U1 -xThxBe13 . We examine tunneling conductance spectra for two competitive scenarios in U1 -xThxBe13 —the degenerate Eu scenario and the accidental scenario.

  12. Symmetries of Ginsparg-Wilson Chiral Fermions

    OpenAIRE

    Mandula, Jeffrey E.

    2009-01-01

    The group structure of the variant chiral symmetry discovered by Luscher in the Ginsparg-Wilson description of lattice chiral fermions is analyzed. It is shown that the group contains an infinite number of linearly independent symmetry generators, and the Lie algebra is given explicitly. CP is an automorphism of this extended chiral group, and the CP transformation properties of the symmetry generators are found. The group has an infinite-parameter invariant subgroup, and the factor group, wh...

  13. Inverse semigroups the theory of partial symmetries

    CERN Document Server

    Lawson, Mark V

    1998-01-01

    Symmetry is one of the most important organising principles in the natural sciences. The mathematical theory of symmetry has long been associated with group theory, but it is a basic premise of this book that there are aspects of symmetry which are more faithfully represented by a generalization of groups called inverse semigroups. The theory of inverse semigroups is described from its origins in the foundations of differential geometry through to its most recent applications in combinatorial group theory, and the theory tilings.

  14. Systems with Symmetry Breaking and Restoration

    Directory of Open Access Journals (Sweden)

    Vyacheslav I. Yukalov

    2010-01-01

    Full Text Available Statistical systems, in which spontaneous symmetry breaking can be accompanied by spontaneous local symmetry restoration, are considered. A general approach to describing such systems is formulated, based on the notion of weighted Hilbert spaces and configuration averaging. The approach is illustrated by the example of a ferroelectric with mesoscopic fluctuations of paraelectric phase. The influence of the local symmetry restoration on the system characteristics, such as sound velocity and Debye-Waller factor, is discussed.

  15. Anomalous Mirror Symmetry Generated by Optical Illusion

    Directory of Open Access Journals (Sweden)

    Kokichi Sugihara

    2016-04-01

    Full Text Available This paper introduces a new concept of mirror symmetry, called “anomalous mirror symmetry”, which is physically impossible but can be perceived by human vision systems because of optical illusion. This symmetry is characterized geometrically and a method for creating cylindrical surfaces that create this symmetry is constructed. Examples of solid objects constructed by a 3D printer are also shown.

  16. The near-symmetry of proteins.

    Science.gov (United States)

    Bonjack-Shterengartz, Maayan; Avnir, David

    2015-04-01

    The majority of protein oligomers form clusters which are nearly symmetric. Understanding of that imperfection, its origins, and perhaps also its advantages requires the conversion of the currently used vague qualitative descriptive language of the near-symmetry into an accurate quantitative measure that will allow to answer questions such as: "What is the degree of symmetry deviation of the protein?," "how do these deviations compare within a family of proteins?," and so on. We developed quantitative methods to answer this type of questions, which are capable of analyzing the whole protein, its backbone or selected portions of it, down to comparison of symmetry-related specific amino-acids, and which are capable of visualizing the various levels of symmetry deviations in the form of symmetry maps. We have applied these methods on an extensive list of homomers and heteromers and found that apparently all proteins never reach perfect symmetry. Strikingly, even homomeric protein clusters are never ideally symmetric. We also found that the main burden of symmetry distortion is on the amino-acids near the symmetry axis; that it is mainly the more hydrophilic amino-acids that take place in symmetry-distortive interactions; and more. The remarkable ability of heteromers to preserve near-symmetry, despite the different sequences, was also shown and analyzed. The comprehensive literature on the suggested advantages symmetric oligomerizations raises a yet-unsolved key question: If symmetry is so advantageous, why do proteins stop shy of perfect symmetry? Some tentative answers to be tested in further studies are suggested in a concluding outlook. © 2014 Wiley Periodicals, Inc.

  17. Site symmetry and crystal symmetry: a spherical tensor analysis

    Energy Technology Data Exchange (ETDEWEB)

    Brouder, Christian; Juhin, Amelie; Bordage, Amelie; Arrio, Marie-Anne [Institut de Mineralogie et de Physique des Milieux Condenses, CNRS UMR 7590, Universites Paris 6 et 7, IPGP, 140 rue de Lourmel, 75015 Paris (France)], E-mail: christian.brouder@impmc.jussieu.fr

    2008-11-12

    The relation between the properties of a specific crystallographic site and the properties of the full crystal is discussed by using spherical tensors. The concept of spherical tensors is introduced and the way it transforms under the symmetry operations of the site and from site to site is described in detail. The law of spherical tensor coupling is given and illustrated with the example of the electric dipole and quadrupole transitions in x-ray absorption spectroscopy. The main application of the formalism is the reduction of computation time in the calculation of the properties of crystals by band-structure methods. The general approach is illustrated by the examples of substitutional chromium in spinel and substitutional vanadium in garnet.

  18. 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).

  19. Anisotropy of S wave velocity in the lowermost mantle using broad-band data recorded at Syowa in Antarctica

    Science.gov (United States)

    Usui, Y.; Hiramatsu, Y.; Furumoto, M.; Kanao, M.

    2003-12-01

    We investigate the velocity structure of the lowermost mantle (D") beneath the Antarctic Ocean. We analyze seismograms from 16 deep earthquakes in south Pacific subduction zones from 1990 to 2001 recorded by STS-1 broad-band seismographs at Syowa station in Antarctica. The source-receiver combinations span distances range 85\\deg-95\\deg with associated S waves passing through D" beneath the Antarctic ocean. Differential travel times of split S waves are estimated to be up to 2s, showing that longitudinal components (SV) energy arrives earlier than transverse components (SH) energy. The absence of significant splitting for S waves with turning points more than four hundred kilometers above the core-mantle boundary (CMB) indicates that anisotropy is localized within the D" region. Differential travel times among S, ScS and SKS phases and waveform modeling are used to construct the velocity structure in D". We calculate synthetic waveforms by the Direct Solution Method (DSM: Geller and Ohminato, 1994; Geller and Takeuchi, 1995). SH shows a double arrival at the epicentral distance near 89\\deg. However SV in this range remains a single arrival. Isotropic model_@can not explain these observation. We find that synthetics for transverse isotropic models with SH velocity discontinuity (SYYM model) explain well the observed differential travel times and waveforms. The thickness of the anisotropic zone, where SH wave is faster up to 2.0% than SV wave, estimated to be about 350 km. This study region corresponds to the high velocity region at the lowermost mantle by tomographic studies (Kuo et al., 2000; Masters et al., 2000). This kind of transverse anisotropy correlates with high velocity regions where paleo-slabs may descend into the lower mantle (Kendall and Silver, 1996; Garnero and Lay, 1997). We conclude that these observations may be explained by an anisotropic D" layer and D" layer anisotropy is attributed to the paleo-slab material subducted during 120Myr-180Myr.

  20. Intrinsic and scattering attenuation of high-frequency S-waves in the central part of the External Dinarides

    Science.gov (United States)

    Majstorović, Josipa; Belinić, Tena; Namjesnik, Dalija; Dasović, Iva; Herak, Davorka; Herak, Marijan

    2017-09-01

    The central part of the External Dinarides (CED) is a geologically and tectonically complex region formed in the collision between the Adriatic microplate and the European plate. In this study, the contributions of intrinsic and scattering attenuation ( Q i - 1 and Q sc - 1 , respectively) to the total S-wave attenuation were calculated for the first time. The multiple lapse-time window analysis (MLTWA method), based on the assumptions of multiple isotropic scattering in a homogeneous medium with uniformly distributed scatterers, was applied to seismograms of 450 earthquakes recorded at six seismic stations. Selected events have hypocentral distances between 40 and 90 km with local magnitudes between 1.5 and 4.7. The analysis was performed over 11 frequency bands with central frequencies between 1.5 and 16 Hz. Results show that the seismic albedo of the studied area is less than 0.5 and Q i - 1 > Q sc - 1 at all central frequencies and for all stations. These imply that the intrinsic attenuation dominates over scattering attenuation in the whole study area. Calculated total S-wave and expected coda wave attenuation for CED are in a very good agreement with the ones measured in previous studies using the coda normalization and the coda-Q methods. All estimated attenuation factors decrease with increasing frequency. The intrinsic attenuation for CED is among the highest observed elsewhere, which could be due to the highly fractured and fluid-filled carbonates in the upper crust. The scattering and the total S-wave attenuation for CED are close to the average values obtained in other studies performed worldwide. In particular, good agreement of frequency dependence of total attenuation in CED and in the regions that contributed most strong-motion records for ground motion prediction equations used in PSHA in Croatia indicates that those were well chosen and applicable to this area as far as their attenuation properties are concerned.

  1. Symmetry energy in nuclear density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Nazarewicz, W. [University of Tennessee Knoxville, Department of Physics and Astronomy, Knoxville, Tennessee (United States); Oak Ridge National Laboratory, Oak Ridge, Tennessee (United States); University of Warsaw, Faculty of Physics, Warsaw (Poland); Reinhard, P.G. [Universitaet Erlangen/Nuernberg, Institut fuer Theoretische Physik, Erlangen (Germany); Satula, W. [University of Warsaw, Faculty of Physics, Warsaw (Poland); Vretenar, D. [University of Zagreb, Physics Department, Faculty of Science, Zagreb (Croatia)

    2014-02-15

    The nuclear symmetry energy represents a response to the neutron-proton asymmetry. In this paper we discuss various aspects of symmetry energy in the framework of nuclear density functional theory, considering both non-relativistic and relativistic self-consistent mean-field realizations side by side. Key observables pertaining to bulk nucleonic matter and finite nuclei are reviewed. Constraints on the symmetry energy and correlations between observables and symmetry energy parameters, using statistical covariance analysis, are investigated. Perspectives for future work are outlined in the context of ongoing experimental efforts. (orig.)

  2. Noether gauge symmetry approach in quintom cosmology

    Science.gov (United States)

    Aslam, Adnan; Jamil, Mubasher; Momeni, Davood; Myrzakulov, Ratbay; Rashid, Muneer Ahmad; Raza, Muhammad

    2013-12-01

    In literature usual point like symmetries of the Lagrangian have been introduced to study the symmetries and the structure of the fields. This kind of Noether symmetry is a subclass of a more general family of symmetries, called Noether gauge symmetries (NGS). Motivated by this mathematical tool, in this paper, we study the generalized Noether symmetry of quintom model of dark energy, which is a two component fluid model with quintessence and phantom scalar fields. Our model is a generalization of the Noether symmetries of a single and multiple components which have been investigated in detail before. We found the general form of the quintom potential in which the whole dynamical system has a point like symmetry. We investigated different possible solutions of the system for diverse family of gauge function. Specially, we discovered two family of potentials, one corresponds to a free quintessence (phantom) and the second is in the form of quadratic interaction between two components. These two families of potential functions are proposed from the symmetry point of view, but in the quintom models they are used as phenomenological models without clear mathematical justification. From integrability point of view, we found two forms of the scale factor: one is power law and second is de-Sitter. Some cosmological implications of the solutions have been investigated.

  3. Chaotic inflation in supergravity with Heisenberg symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Antusch, Stefan [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Muenchen (Germany); Bastero-Gil, Mar [Departamento de Fisica Teorica y del Cosmos and Centro Andaluz de Fisica de Particulas Elementales, Universidad de Granada, 19071 Granada (Spain); Dutta, Koushik [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Muenchen (Germany)], E-mail: koushik@mppmu.mpg.de; King, Steve F. [School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ (United Kingdom); Kostka, Philipp M. [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Muenchen (Germany)

    2009-09-07

    We propose the introduction of a Heisenberg symmetry of the Kaehler potential to solve the problems with chaotic inflation in supergravity, as a viable alternative to the use of shift symmetry. The slope of the inflaton potential emerges from a small Heisenberg symmetry breaking term in the superpotential. The modulus field of the Heisenberg symmetry is stabilized and made heavy with the help of the large vacuum energy density during inflation. The observable predictions are indistinguishable from those of typical chaotic inflation models, however the form of the inflationary superpotential considered here may be interpreted in terms of sneutrino inflation arising from certain classes of string theory.

  4. Chaotic inflation in supergravity with Heisenberg symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Antusch, Stefan; Dutta, Koushik; Kostka, Philipp M. [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Muenchen (Germany); Bastero-Gil, Mar [Departamento de Fisica Teorica y del Cosmos, Centro Andaluz de Fisica de Particulas Elementales, Universidad de Granada, 19071 Granada (Spain); King, Steve F. [School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ (United Kingdom)

    2010-07-01

    We propose the introduction of a Heisenberg symmetry of the Kaehler potential to solve the problems with chaotic inflation in supergravity, as a viable alternative to the use of shift symmetry. The slope of the inflaton potential emerges from a small Heisenberg symmetry breaking term in the superpotential. The modulus field of the Heisenberg symmetry is stabilized and made heavy with the help of the large vacuum energy density during inflation. The observable predictions are indistinguishable from those of typical chaotic inflation models, however the form of the inflationary superpotential considered here may be interpreted in terms of sneutrino inflation.

  5. ``Gauging'' Non-on-site Symmetries and Symmetry Protected Topological Phases

    Science.gov (United States)

    Hsieh, Chang-Tse; Cho, Gil Young; Ryu, Shinsei

    2015-03-01

    We gauge non-on-site symmetries, such as parity symmetries, for a general (1+1)D conformal field theory (CFT) which is the boundary of (2+1)D symmetry protected topological (SPT) phases. This provides an efficient method to diagnose stability of SPT phases with the discrete non-on-site symmetries. To gauge the non-on- site symmetries, we are naturally led to consider field theories defined on a non-orientied manifold, such as Klein bottle. The partner states of the ``vortices'' (or twist operators) of the gauged non-on-site symmetries, the so-called crosscap states, provide information about the classification of the corresponding SPT phases. Our method also provide a way to gauging time-reversal symmetry, which is ``topologically'' related to parity symmetry by CPT theorem. NSF Grants DMR-1064319.

  6. PREFACE: Symmetries in Science XV

    Science.gov (United States)

    Schuch, Dieter; Ramek, Michael

    2012-08-01

    Logo Bregenz, the peaceful monastery of Mehrerau and the Opera on the Floating Stage again provided the setting for the international symposium 'Symmetries in Science'. The series which has been running for more than 30 years brings together leading theoreticians whose area of research is, in one way or another, related to symmetry. Since 1992 the meeting took place biannually in Brengez until 2003. In 2009, with the endorsement of the founder, Professor Bruno Gruber, we succeeded in re-establishing the series without external funding. The resounding success of that meeting encouraged us to continue in 2011 and, following on the enthusiasm and positive feedback of the participants, we expect to continue in 2013. Yet again, our meeting in 2011 was very international in flavour and brought together some 30 participants representing 12 nationalities, half of them from countries outside the European Union (from New Zealand to Mexico, Russia to Israel). The broad spectrum, a mixture of experienced experts and highly-motivated newcomers, the intensive exchange of ideas in a harmonious and relaxed atmosphere and the resulting joint projects are probably the secrets of why this meeting is considered to be so special to its participants. At the resumption in 2009 some leading experts and younger scientists from economically weak countries were unable to attend due to the lack of financial resources. This time, with the very worthy and unbureaucratic support of the 'Vereinigung von Freunden und Förderern der J W Goethe-Universität Frankfurt am Main' (in short: 'Friends and Supporters of the Frankfurt University'), it was possible for all candidates to participate. In particular some young, inspired scientists had the chance of presenting their work to a very competent, but also friendly, audience. We wish to thank the 'Freunde und Förderer' for supporting Symmetries in Science XV. Almost all participants contributed to the publication of this Conference Proceedings. There

  7. Lower critical field and SNS-Andreev spectroscopy of 122-arsenides: Evidence of nodeless superconducting gap

    Science.gov (United States)

    Abdel-Hafiez, M.; Pereira, P. J.; Kuzmichev, S. A.; Kuzmicheva, T. E.; Pudalov, V. M.; Harnagea, L.; Kordyuk, A. A.; Silhanek, A. V.; Moshchalkov, V. V.; Shen, B.; Wen, Hai-Hu; Vasiliev, A. N.; Chen, Xiao-Jia

    2014-08-01

    Using two experimental techniques, we studied single crystals of the 122-FeAs family with almost the same critical temperature, Tc. We investigated the temperature dependence of the lower critical field Hc1(T ) of a Ca0.32Na0.68Fe2As2 (Tc≈34K) single crystal under static magnetic fields H parallel to the c axis. The temperature dependence of the London penetration depth can be described equally well either by a single anisotropic s-wave-like gap or by a two-gap model, while a d-wave approach cannot be used to fit the London penetration depth data. Intrinsic multiple Andreev reflection effect spectroscopy was used to detect bulk gap values in single crystals of the intimate compound Ba0.65K0.35Fe2As2, with the same Tc. We estimated the range of the large gap value ΔL=6-8 meV (depending on small variation of Tc) and its a k space anisotropy of about 30%, and the small gap ΔS≈1.7±0.3 meV. This clearly indicates that the gap structure of our investigated systems more likely corresponds to a nodeless s-wave two gaps.

  8. Seismic velocity structure of the Guerrero gap, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Dominguez, Jaime [Colegio de Ciencias y Humanidades, Plantel Sur, Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico); Suarez, Gerardo [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico); Comte, Diana [Departamento de Geofisica, Universidad de Chile, Santiago (Chile); Quintanar, Luis [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)

    2006-04-15

    A two-dimensional velocity structure of the Guerrero gap was obtained by applying a damped least square method to hypocenters of local seismicity recorded by a telemetric network situated on the Guerrero coast, above Cocos plate subduction zone. The region was parameterized by a mesh of 64 cubes in six layers, a total of 384 blocks. The results of 3-D inversion showed that differences of P-wave velocity values among blocks along the strike of the subduction zone were {approx}0.25 km/s, effectively showing a two-dimensional symmetry. A 2-D inversion taking into account velocity similarities among the 2-D bands generated megablocks. A final inversion procedure yields P-wave velocity values ranging from 5.4 to 8.2 km/s, and S-wave values from 3.2 and 4.7 km/s, suggesting a continental crust with a thickness of {approx}32 km composed of four flat megablocks with a P-wave velocity interval of 5.4 to 7.1 km/s. The Moho interface lies at {approx}32 km depth and above a mantle wedge between continental and oceanic crust. The downgoing oceanic crust has three layers (7.2-7.7 km/s), dipping at an angle of {approx}26 degrees. A sharp velocity change at a depth of {approx}30 km suggests a phase change from basalt to eclogite (7.2 to 7.6 km/s). The mantle has an average velocity of 8.2 km/s. The new velocity model reduced the error in locations and fits better the characteristics of the Guerrero gap. [Spanish] Se obtiene la estructura bidimensional de velocidades sismicas de la brecha de Guerrero aplicando el metodo de minimos cuadrados amortiguados a los datos de la sismicidad local registrada por una red telemetrica situada en la costa, ubicada en la zona de subduccion de la placa de Cocos. La region se parametrizo con una malla de 64 cubos en seis capas, un total de 384 bloques. Los resultados de esta inversion tridimensional (3-D) mostraron una diferencia de velocidad de onda P, entre bloques adyacentes y paralelos a la costa, no mayor de 0.25 km/s, mostrando una simetria

  9. Finite temperature study of the axial U(1) symmetry on the lattice with overlap fermion formulation

    Science.gov (United States)

    Cossu, Guido; Aoki, Sinya; Fukaya, Hidenori; Hashimoto, Shoji; Kaneko, Takashi; Matsufuru, Hideo; Noaki, Jun-Ichi

    2013-06-01

    We examine the axial U(1) symmetry near and above the finite-temperature phase transition in two-flavor QCD using lattice QCD simulations. Although the axial U(1) symmetry is always violated by quantization, i.e., the chiral anomaly, the correlation functions may manifest effective restoration of the symmetry in the high-temperature phase. We explicitly study this possibility by calculating the meson correlators as well as the Dirac operator spectral density near the critical point. Our numerical simulations are performed on a 163×8 lattice with two flavors of dynamical quarks represented by the overlap fermion formalism. Chiral symmetry and its violation due to the axial anomaly is manifestly realized with this formulation, which is a prerequisite for the study of the effective restoration of the axial U(1) symmetry. In order to avoid discontinuity in the gauge configuration space, which occurs for the exactly chiral lattice fermions, the simulation is confined in a fixed topological sector. It induces a finite-volume effect, which is well described by a formula based on the Fourier transform from the θ vacua. We confirm this formula at finite temperature by calculating the topological susceptibility in the quenched theory. Our two-flavor simulations show degeneracy of the meson correlators and a gap in the Dirac operator spectral density, which implies that the axial U(1) symmetry is effectively restored in the chirally symmetric phase.

  10. Probing the pairing symmetry of the iron pnictides with electronic Raman scattering

    Energy Technology Data Exchange (ETDEWEB)

    Boyd, G.R.

    2010-04-29

    An important issue in the study of the iron-arsenic based superconductors is the symmetry of the superconducting gap, a problem complicated by multiple gaps on different Fermi surface sheets. Electronic Raman scattering is a flexible bulk probe which allows one in principle to determine gap magnitudes and test for gap nodes in different regions of the Brillouin zone by employing different photon polarization states. Here we calculate the clean Raman intensity for A{sub 1g}, B{sub 1g} and B{sub 2g} polarizations, and discuss the peak structures and low-energy power laws which might be expected for several popular models of the superconducting gap in these systems.

  11. Three-dimensional S-wave velocity model of the Bohemian Massif from Bayesian ambient noise tomography

    Science.gov (United States)

    Valentová, Lubica; Gallovič, František; Maierová, Petra

    2017-10-01

    We perform two-step surface wave tomography of phase-velocity dispersion curves obtained by ambient noise cross-correlations in the Bohemian Massif. In the first step, the inter-station dispersion curves were inverted for each period (ranging between 4 and 20 s) separately into phase-velocity maps using 2D adjoint method. In the second step, we perform Bayesian inversion of the set of the phase-velocity maps into an S-wave velocity model. To sample the posterior probability density function, the parallel tempering algorithm is employed providing over 1 million models. From the model samples, not only mean model but also its uncertainty is determined to appraise the reliable features. The model is correlated with known main geologic structures of the Bohemian Massif. The uppermost low-velocity anomalies are in agreement with thick sedimentary basins. In deeper parts (4-20 km), the S-wave velocity anomalies correspond, in general, to main tectonic domains of the Bohemian Massif. The exception is a stable low-velocity body in the middle of the high-velocity Moldanubian domain and high-velocity body resembling a promontory of the Moldanubian into the Teplá-Barrandian domain. The most pronounced (high-velocity) anomaly is located beneath the Eger Rift that is a part of a Tertiary rift system across Europe.

  12. The Study on S-Wave Velocity Structure of Upper Crust in Three Gorges Region of Yangtze River

    Science.gov (United States)

    Li, X.; Zhu, P.; Zhou, Q.

    2014-12-01

    The profile of S-wave velocity structure along Badong-Maoping-Tumen is presented using the ambient noise data observed at 10 stations from mobile broadband seismic array which is located at Three Gorges Region. All of available vertical component time series during April and May,2011 have been cross-correlated to estimate the empirical Green functions. Group velocity dispersion curves were measured by applying multiple filtering technique. Using these dispersion curves,we obtain high resolution pure-path dispersions at 0.5-10 second periods. The S-wave velocity structure,which was reconstructed by inverting the pure-path dispersions,reveals the velocity variations of upper crust at Three Gorges Region. Main conclusions are as follows:(1)The velocity variations in the study region have a close relationship with the geological structure and the velocity profile suggests a anticline unit which core area is Huangling block;(2)The relative fast velocity variations beneath Jiuwanxi and its surrounding areas may correspond to the geological structure and earthquake activity there;(3) The high velocity of the upper crustal in Sandouping indicates that the Reservoir Dam of Three Gorges is located at a tectonic stable region.

  13. P Wave and S Wave Acoustic Velocities of Partial Molten Peridotite at Mantle P-T and MHz Frequencies

    Science.gov (United States)

    Weidner, D. J.; Li, L.; Whitaker, M. L.; Triplett, R.

    2016-12-01

    The speed that acoustic waves travel in a partially molten peridotite are crucial parameters to detect not only the presence of melt in the Earth's deep interior, but also understand many issues about the structure and dynamics of the mantle. Technical challenges have hindered such measurements in the laboratory. Here we report the experimental results on the ultrasonic acoustic wave velocities in a partial molten peridotite using multi-anvil high pressure apparatus located at beamline BM6 Advance Photon Source. We use the newly installed ultrasonic equipment using the pulse-echo-overlap method coupled with D-DIA device. X-ray radiography is used to measure sample length at high P-T. The X-ray diffraction spectrum is used to determine the pressure and sample conditions. Precise measurements of P and S wave velocities are obtained at 60 and 35 MHz respectively and are nearly simultaneous. We use a double reflector method to enable measurement of elastic wave velocities of cold-pressed polycrystalline sample which is sintered in situ at high P-T. Experiments were carried out up to 3 GPa and 1500 oC. Our preliminary results indicate that the KLB1 peridotite sample experienced a few percent decrease of both p and s wave velocities as partial melting occurs. The data define a small decrease in the bulk modulus as well as the shear modulus upon melting. This implies that dynamic melting is a significant process at megahertz frequencies.

  14. Blobs strengthen repetition but weaken symmetry

    NARCIS (Netherlands)

    Csathó, A.I.; Vloed, G. van der; Helm, P.A. van der

    2003-01-01

    The human visual system is more sensitive to symmetry than to repetition. According to the so-called holographic approach [J. Math. Psychol. 35 (1991) 151; Psychol. Rev. 103 (1996) 429; Psychol. Rev. 106 (1999) 622], however, this perceptual difference between symmetry and repetition depends

  15. Symmetries of nonlinear ordinary differential equations: The ...

    Indian Academy of Sciences (India)

    2015-10-21

    Oct 21, 2015 ... Lie symmetry analysis is one of the powerful tools to analyse nonlinear ordinary dif- ferential equations. We review the effectiveness of this method in terms of various symmetries. We present the method .... coincides with the linearized equation, then the underlying system is self-adjoint and in this case the ...

  16. Symmetry : Between indecision and equality of choice

    NARCIS (Netherlands)

    Barakova, EI; Spaanenburg, L; Mira, J; MorenoDiaz, R; Cabestany, J

    1997-01-01

    The training of a neural network is an intricate balance between knowledge, randomness and symmetry. Symmetry can both be beneficial and detrimental to the learning process by respectively equality of choice and indecision. The paper provides a critical review and classification, and offers a

  17. Nuclear symmetry energy: An experimental overview

    Indian Academy of Sciences (India)

    Abstract. The nuclear symmetry energy is a fundamental quantity important for study- ing the structure of systems as diverse as the atomic nucleus and the neutron star. Con- siderable efforts are being made to experimentally extract the symmetry energy and its dependence on nuclear density and temperature. In this article ...

  18. The golden ratio in facial symmetry

    NARCIS (Netherlands)

    Prokopakis, E. P.; Vlastos, I. M.; Picavet, V. A.; Nolst Trenite, G.; Thomas, R.; Cingi, C.; Hellings, P. W.

    2013-01-01

    Symmetry is believed to be a hallmark of appealing faces. However, this does not imply that the most aesthetically pleasing proportions are necessary those that arise from the simple division of the face into thirds or fifths. Based on the etymology of the word symmetry, as well as on specific

  19. Mathematical models of spontaneous symmetry breaking

    OpenAIRE

    Sardanashvily, G.

    2008-01-01

    The Higgs mechanism of mass generation is the main ingredient in the contemporary Standard Model and its various generalizations. However, there is no comprehensive theory of spontaneous symmetry breaking. We summarize the relevant mathematical results characterizing spontaneous symmetry breaking phenomena in algebraic quantum theory, axiomatic quantum field theory, group theory, and classical gauge theory.

  20. Superfield approach to symmetry invariance in quantum ...

    Indian Academy of Sciences (India)

    (anti-)BRST symmetry transformations that are associated with the matter fields of the above interacting 1-form gauge ... in some sense, generalized) so as to derive the nilpotent (anti-)BRST symmetry transformations ...... One of the central objectives of our present investigation was to understand the geometrical meaning of ...

  1. Symmetry breaking signaling mechanisms during cell polarization

    NARCIS (Netherlands)

    Bruurs, LJM|info:eu-repo/dai/nl/413640779

    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.

  2. Nuclear symmetry energy: An experimental overview

    Indian Academy of Sciences (India)

    The nuclear symmetry energy is a fundamental quantity important for studying the structure of systems as diverse as the atomic nucleus and the neutron star. Considerable efforts are being made to experimentally extract the symmetry energy and its dependence on nuclear density and temperature. In this article, the ...

  3. Solution of the gap equation in neutron matter

    Energy Technology Data Exchange (ETDEWEB)

    Khodel, V.A. [Washington Univ., St. Louis, MO (United States). Dept. of Physics; Khodel, V.V. [Washington Univ., St. Louis, MO (United States). Dept. of Physics; Clark, J.W. [Washington Univ., St. Louis, MO (United States). Dept. of Physics

    1996-03-04

    The problem of solving the gap equation for S-wave pairing in pure neutron matter is considered for the case that the pairing matrix elements V(p,p`) are calculated directly from a realistic bare neutron-neutron potential containing a strong short-range repulsion. The original gap equation is replaced identically by a coupled set of equations: a non-singular quasilinear integral equation for the dimensionless gap function {chi}(p) defined by {Delta}(p)={Delta}{sub F}{chi}(p) and a non-linear algebraic equation for the gap magnitude {Delta}{sub F}={Delta}(p{sub F}) at the Fermi surface. This reformulation admits a robust and rapidly convergent iteration procedure for the determination of the gap function. The treatment may be extended to singlet or triplet pairing in non-zero angular momentum states. S-wave pairing is investigated numerically for the Reid-soft-core interaction. Although the pairing matrix elements of this potential are everywhere positive, non-trivial solutions of the gap equation are obtained on the range 0 < p{sub F} < p{sub c}=1.7496.. fm{sup -1} of Fermi momenta, with the gap parameter {Delta}{sub F} reaching a maximum of some 3 MeV near p{sub F}=0.85 fm{sup -1}. Numerical results are also provided for the highly realistic Argonne v{sub 14} and v{sub 18} interactions. Within the context of the new computational scheme, a condition for closure of the gap is derived in terms of the first zero p{sub 0} of the gap function {Delta}(p). It is shown that {Delta}{sub F} vanishes exponentially not only in the low-density limit p{sub F}{yields}0, but also as the Fermi momentum rises and approaches the upper critical value p{sub c} specified by p{sub F}=p{sub 0}(p{sub F}), beyond which there exists no non-trivial solution of the gap equation. The numerical results for the function {Delta}(p) in neutron matter display a remarkable universality of structure, visible especially in the stability of p{sub 0} under variation of density. (orig./WL).

  4. Dirac mass generation from crystal symmetry breaking on the surfaces of topological crystalline insulators.

    Science.gov (United States)

    Zeljkovic, Ilija; Okada, Yoshinori; Serbyn, Maksym; Sankar, R; Walkup, Daniel; Zhou, Wenwen; Liu, Junwei; Chang, Guoqing; Wang, Yung Jui; Hasan, M Zahid; Chou, Fangcheng; Lin, Hsin; Bansil, Arun; Fu, Liang; Madhavan, Vidya

    2015-03-01

    The tunability of topological surface states and controllable opening of the Dirac gap are of fundamental and practical interest in the field of topological materials. In the newly discovered topological crystalline insulators (TCIs), theory predicts that the Dirac node is protected by a crystalline symmetry and that the surface state electrons can acquire a mass if this symmetry is broken. Recent studies have detected signatures of a spontaneously generated Dirac gap in TCIs; however, the mechanism of mass formation remains elusive. In this work, we present scanning tunnelling microscopy (STM) measurements of the TCI Pb1-xSnxSe for a wide range of alloy compositions spanning the topological and non-topological regimes. The STM topographies reveal a symmetry-breaking distortion on the surface, which imparts mass to the otherwise massless Dirac electrons-a mechanism analogous to the long sought-after Higgs mechanism in particle physics. Interestingly, the measured Dirac gap decreases on approaching the trivial phase, whereas the magnitude of the distortion remains nearly constant. Our data and calculations reveal that the penetration depth of Dirac surface states controls the magnitude of the Dirac mass. At the limit of the critical composition, the penetration depth is predicted to go to infinity, resulting in zero mass, consistent with our measurements. Finally, we discover the existence of surface states in the non-topological regime, which have the characteristics of gapped, double-branched Dirac fermions and could be exploited in realizing superconductivity in these materials.

  5. Tests of Gravitational Symmetries with Radio Pulsars

    CERN Document Server

    Shao, Lijing

    2016-01-01

    Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universality of free fall for self-gravitating bodies, time-shift symmetry in the gravitational constant, local position invariance and local Lorentz invariance of gravity, and spacetime translational symmetries. Recent experimental explorations for post-Newtonian gravity are discussed, of which, those from pulsar astronomy are highlighted. All of these tests, of very different aspects of gravity theories, at very different length scales, favor to very high precision the predictions of the strong equivalence principle (SEP) and, in particular, general relativity which embodies SEP completely. As the founding principles of gravity, these symmetries are motivated to be promoted to even stricter tests in future.

  6. Complex Networks and Symmetry I: A Review

    Directory of Open Access Journals (Sweden)

    Riccardo Basosi

    2010-09-01

    Full Text Available In this review we establish various connections between complex networks and symmetry. While special types of symmetries (e.g., automorphisms are studied in detail within discrete mathematics for particular classes of deterministic graphs, the analysis of more general symmetries in real complex networks is far less developed. We argue that real networks, as any entity characterized by imperfections or errors, necessarily require a stochastic notion of invariance. We therefore propose a definition of stochastic symmetry based on graph ensembles and use it to review the main results of network theory from an unusual perspective. The results discussed here and in a companion paper show that stochastic symmetry highlights the most informative topological properties of real networks, even in noisy situations unaccessible to exact techniques.

  7. Anomalous Symmetry Fractionalization and Surface Topological Order

    Directory of Open Access Journals (Sweden)

    Xie Chen

    2015-10-01

    Full Text Available In addition to possessing fractional statistics, anyon excitations of a 2D topologically ordered state can realize symmetry in distinct ways, leading to a variety of symmetry-enriched topological (SET phases. While the symmetry fractionalization must be consistent with the fusion and braiding rules of the anyons, not all ostensibly consistent symmetry fractionalizations can be realized in 2D systems. Instead, certain “anomalous” SETs can only occur on the surface of a 3D symmetry-protected topological (SPT phase. In this paper, we describe a procedure for determining whether a SET of a discrete, on-site, unitary symmetry group G is anomalous or not. The basic idea is to gauge the symmetry and expose the anomaly as an obstruction to a consistent topological theory combining both the original anyons and the gauge fluxes. Utilizing a result of Etingof, Nikshych, and Ostrik, we point out that a class of obstructions is captured by the fourth cohomology group H^{4}(G,U(1, which also precisely labels the set of 3D SPT phases, with symmetry group G. An explicit procedure for calculating the cohomology data from a SET is given, with the corresponding physical intuition explained. We thus establish a general bulk-boundary correspondence between the anomalous SET and the 3D bulk SPT whose surface termination realizes it. We illustrate this idea using the chiral spin liquid [U(1_{2}] topological order with a reduced symmetry Z_{2}×Z_{2}⊂SO(3, which can act on the semion quasiparticle in an anomalous way. We construct exactly solved 3D SPT models realizing the anomalous surface terminations and demonstrate that they are nontrivial by computing three-loop braiding statistics. Possible extensions to antiunitary symmetries are also discussed.

  8. Translational Symmetry and Microscopic Constraints on Symmetry-Enriched Topological Phases: A View from the Surface

    Directory of Open Access Journals (Sweden)

    Meng Cheng

    2016-12-01

    Full Text Available The Lieb-Schultz-Mattis theorem and its higher-dimensional generalizations by Oshikawa and Hastings require that translationally invariant 2D spin systems with a half-integer spin per unit cell must either have a continuum of low energy excitations, spontaneously break some symmetries, or exhibit topological order with anyonic excitations. We establish a connection between these constraints and a remarkably similar set of constraints at the surface of a 3D interacting topological insulator. This, combined with recent work on symmetry-enriched topological phases with on-site unitary symmetries, enables us to develop a framework for understanding the structure of symmetry-enriched topological phases with both translational and on-site unitary symmetries, including the effective theory of symmetry defects. This framework places stringent constraints on the possible types of symmetry fractionalization that can occur in 2D systems whose unit cell contains fractional spin, fractional charge, or a projective representation of the symmetry group. As a concrete application, we determine when a topological phase must possess a “spinon” excitation, even in cases when spin rotational invariance is broken down to a discrete subgroup by the crystal structure. We also describe the phenomena of “anyonic spin-orbit coupling,” which may arise from the interplay of translational and on-site symmetries. These include the possibility of on-site symmetry defect branch lines carrying topological charge per unit length and lattice dislocations inducing degeneracies protected by on-site symmetry.

  9. Efficient Symmetry Reduction and the Use of State Symmetries for Symbolic Model Checking

    Directory of Open Access Journals (Sweden)

    Christian Appold

    2010-06-01

    Full Text Available One technique to reduce the state-space explosion problem in temporal logic model checking is symmetry reduction. The combination of symmetry reduction and symbolic model checking by using BDDs suffered a long time from the prohibitively large BDD for the orbit relation. Dynamic symmetry reduction calculates representatives of equivalence classes of states dynamically and thus avoids the construction of the orbit relation. In this paper, we present a new efficient model checking algorithm based on dynamic symmetry reduction. Our experiments show that the algorithm is very fast and allows the verification of larger systems. We additionally implemented the use of state symmetries for symbolic symmetry reduction. To our knowledge we are the first who investigated state symmetries in combination with BDD based symbolic model checking.

  10. Single Nodal Loop of Accidental Degeneracies in Minimal Symmetry: Triclinic CaAs3

    Science.gov (United States)

    Quan, Y.; Yin, Z. P.; Pickett, W. E.

    2017-04-01

    The existence of closed loops of degeneracies in crystals has been intimately connected with associated crystal symmetries, raising the following question: What is the minimum symmetry required for topological character, and can one find an example? Triclinic CaAs3 , in the space group P 1 ¯ with only a center of inversion, has been found to display, without need for tuning, a nodal loop of accidental degeneracies with topological character, centered on one face of the Brillouin zone that is otherwise fully gapped. The small loop is very flat in energy, yet is cut four times by the Fermi energy, a condition that results in an intricate repeated touching of inversion related pairs of Fermi surfaces at Weyl points. Spin-orbit coupling lifts the fourfold degeneracy along the loop, leaving trivial Kramers pairs. With its single nodal loop that emerges without protection from any point group symmetry, CaAs3 represents the primal "hydrogen atom" of nodal loop systems.

  11. Chlorophylls, Symmetry, Chirality, and Photosynthesis

    Directory of Open Access Journals (Sweden)

    Mathias O. Senge

    2014-09-01

    Full Text Available Chlorophylls are a fundamental class of tetrapyrroles and function as the central reaction center, accessory and photoprotective pigments in photosynthesis. Their unique individual photochemical properties are a consequence of the tetrapyrrole macrocycle, the structural chemistry and coordination behavior of the phytochlorin system, and specific substituent pattern. They achieve their full potential in solar energy conversion by working in concert in highly complex, supramolecular structures such as the reaction centers and light-harvesting complexes of photobiology. The biochemical function of these structures depends on the controlled interplay of structural and functional principles of the apoprotein and pigment cofactors. Chlorophylls and bacteriochlorophylls are optically active molecules with several chiral centers, which are necessary for their natural biological function and the assembly of their supramolecular complexes. However, in many cases the exact role of chromophore stereochemistry in the biological context is unknown. This review gives an overview of chlorophyll research in terms of basic function, biosynthesis and their functional and structural role in photosynthesis. It highlights aspects of chirality and symmetry of chlorophylls to elicit further interest in their role in nature.

  12. Structural symmetry in evolutionary games

    Science.gov (United States)

    McAvoy, Alex; Hauert, Christoph

    2015-01-01

    In evolutionary game theory, an important measure of a mutant trait (strategy) is its ability to invade and take over an otherwise-monomorphic population. Typically, one quantifies the success of a mutant strategy via the probability that a randomly occurring mutant will fixate in the population. However, in a structured population, this fixation probability may depend on where the mutant arises. Moreover, the fixation probability is just one quantity by which one can measure the success of a mutant; fixation time, for instance, is another. We define a notion of homogeneity for evolutionary games that captures what it means for two single-mutant states, i.e. two configurations of a single mutant in an otherwise-monomorphic population, to be ‘evolutionarily equivalent’ in the sense that all measures of evolutionary success are the same for both configurations. Using asymmetric games, we argue that the term ‘homogeneous’ should apply to the evolutionary process as a whole rather than to just the population structure. For evolutionary matrix games in graph-structured populations, we give precise conditions under which the resulting process is homogeneous. Finally, we show that asymmetric matrix games can be reduced to symmetric games if the population structure possesses a sufficient degree of symmetry. PMID:26423436

  13. PREFACE: Symmetries in Science XVI

    Science.gov (United States)

    2014-10-01

    This volume of the proceedings ''Symmetries in Science XVI'' is dedicated to the memory of Miguel Lorente and Allan Solomon who both participated several times in these Symposia. We lost not only two great scientists and colleagues, but also two wonderful persons of high esteem whom we will always remember. Dieter Schuch, Michael Ramek There is a German saying ''all good things come in threes'' and ''Symmetries in Science XVI'', convened July 20-26, 2013 at the Mehrerau Monastery, was our third in the sequel of these symposia since taking it over from founder Bruno Gruber who instigated it in 1988 (then in Lochau). Not only the time seemed to have been perfect (one week of beautiful sunshine), but also the medley of participants could hardly have been better. This time, 34 scientists from 16 countries (more than half outside the European Union) came together to report and discuss their latest results in various fields of science, all related to symmetries. The now customary grouping of renowned experts and talented newcomers was very rewarding and stimulating for all. The informal, yet intense, discussions at ''Gasthof Lamm'' occurred (progressively later) each evening till well after midnight and finally till almost daybreak! However, prior to the opening ceremony and during the conference, respectively, we were informed that Miguel Lorente and Allan Solomon had recently passed away. Both attended the SIS Symposia several times and had many friends among present and former participants. Professor Peter Kramer, himself a long-standing participant and whose 80th birthday commemoration prevented him from attending SIS XVI, kindly agreed to write the obituary for Miguel Lorente. Professors Richard Kerner and Carol Penson (both also former attendees) penned, at very short notice, the tribute to Allan Solomon. The obituaries are included in these Proceedings and further tributes have been posted to our conference website. In 28 lectures and an evening poster

  14. Symmetries of Ginsparg-Wilson chiral fermions

    Science.gov (United States)

    Mandula, Jeffrey E.

    2009-10-01

    The group structure of the variant chiral symmetry discovered by Lüscher in the Ginsparg-Wilson description of lattice chiral fermions is analyzed. It is shown that the group contains an infinite number of linearly independent symmetry generators, and the Lie algebra is given explicitly. CP is an automorphism of this extended chiral group, and the CP transformation properties of the symmetry generators are found. The group has an infinite-parameter invariant subgroup, and the factor group, whose elements are its cosets, is isomorphic to the continuum chiral symmetry group. Features of the currents associated with these symmetries are discussed, including the fact that some different, noncommuting symmetry generators lead to the same Noether current. These are universal features of lattice chiral fermions based on the Ginsparg-Wilson relation; they occur in the overlap, domain-wall, and perfect-action formulations. In a solvable example, free overlap fermions, these noncanonical elements of lattice chiral symmetry are related to complex energy singularities that violate reflection positivity and impede continuation to Minkowski space.

  15. Relativity symmetries and Lie algebra contractions

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Dai-Ning; Kong, Otto C.W., E-mail: otto@phy.ncu.edu.tw

    2014-12-15

    We revisit the notion of possible relativity or kinematic symmetries mutually connected through Lie algebra contractions under a new perspective on what constitutes a relativity symmetry. Contractions of an SO(m,n) symmetry as an isometry on an m+n dimensional geometric arena which generalizes the notion of spacetime are discussed systematically. One of the key results is five different contractions of a Galilean-type symmetry G(m,n) preserving a symmetry of the same type at dimension m+n−1, e.g. a G(m,n−1), together with the coset space representations that correspond to the usual physical picture. Most of the results are explicitly illustrated through the example of symmetries obtained from the contraction of SO(2,4), which is the particular case for our interest on the physics side as the proposed relativity symmetry for “quantum spacetime”. The contractions from G(1,3) may be relevant to real physics.

  16. Automatic Affective Evaluation of Visual Symmetry

    Directory of Open Access Journals (Sweden)

    Alexis Makin

    2012-05-01

    Full Text Available It is possible that the neural mechanisms that detect symmetry are linked to those that produce positive affect. We conducted a set of behavioural and electrophysiological studies designed to investigate the nature of this putative connection. First, we used the Implicit Association Test (IAT to measure implicit preference for visual regularity. On some trials, participants saw symmetrical or random dot patterns. On interleaved trials, they saw positive or negative words. When the same button was used to report symmetrical patterns and positive words, response times were faster than when the same button was used to report symmetrical patterns and negative words. This classic IAT effect demonstrated an implicit preference for symmetry. In further experiments, the same procedure was used to record implicit preference for reflection over other types of regularity, such as translation or rotational symmetry. Second, we simultaneously recorded EEG and EMG from the same participants while they observed reflection or random dot patterns. Contrary to previous findings, we found that early visual components (P1 and N1 were modulated by symmetry. Moreover, there was increased activity in the Zygomaticus Major (the muscle responsible for smiling when participants viewed reflectional symmetry, indicating a positive affective response. Rotational symmetry produced different ERPs, and no affective response. Together, our data suggest that, once the patterns are attended, most participants spontaneously form a preference for reflectional symmetry, even in the absence of any explicit instruction to engage in aesthetic evaluation.

  17. Characterization of U.S. Wave Energy Converter (WEC) Test Sites: A Catalogue of Met-Ocean Data.

    Energy Technology Data Exchange (ETDEWEB)

    Dallman, Ann Renee; Neary, Vincent Sinclair

    2014-10-01

    This report presents met - ocean data and wave energy characteristics at three U.S. wave energy converter (WEC) test and potential deployment sites . Its purpose is to enable the compari son of wave resource characteristics among sites as well as the select io n of test sites that are most suitable for a developer's device and that best meet their testing needs and objectives . It also provides essential inputs for the design of WEC test devices and planning WEC tests, including the planning of deployment and op eration s and maintenance. For each site, this report catalogues wave statistics recommended in the (draft) International Electrotechnical Commission Technical Specification (IEC 62600 - 101 TS) on Wave Energy Characterization, as well as the frequency of oc currence of weather windows and extreme sea states, and statistics on wind and ocean currents. It also provides useful information on test site infrastructure and services .

  18. Determination of the {ital S}-wave scattering length in pionic deuterium with a high resolution crystal spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Chatellard, D.; Egger, J.; Jeannet, E. [Institut de Physique de l`Universite, Breguet 1, CH-2000 Neuchatel (Switzerland); Badertscher, A.; Bogdan, M.; Goudsmit, P.F.A.; Leisi, H.J.; Matsinos, E.; Schroeder, H.; Sigg, D.; Zhao, Z.G. [Institut fuer Teilchenphysik der Eidgenoessische Technische Hochschule Zuerich, CH-5232 Villigen PSI (Switzerland); Aschenauer, E.C.; Gabathuler, K.; Hauser, P.; Simons, L.M. [Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Rusi, A.J.; Hassani, E. [Ecole Mohammadia des Ingenieurs, Rabat (Morocco)

    1995-05-22

    The pionic deuterium 3{ital P}{minus}1{ital S} x-ray transition was measured with a quartz crystal spectrometer in combination with a cyclotron trap and charge coupled device detectors. The strong interaction shift and total decay width of the 1{ital S} level are {epsilon}{sub 1{ital S}}(shift)=2.48{plus_minus}0.10 eV (repulsive), {Gamma}{sub 1{ital S}}(width)=1.02{plus_minus}0.21 eV, where the statistical and systematic errors were added linearly. They yield the total pionic deuterium {ital S}-wave scattering length: {ital a}{sub {pi}{sup {minus}}{ital d}}= {minus}0.0264({plus_minus}0.0011)+{ital i}0.0054({plus_minus}0.0011){ital m}{sub {pi}}{sup {minus}1}.

  19. Upper-mantle P- and S-wave velocities below Scandinavia and East Greenland from teleseismic traveltime tomography

    DEFF Research Database (Denmark)

    Hejrani, Babak

    2014-01-01

    This dissertation deals with the resolution of P- and S-velocity variations in the upper mantle (down to 600 km) using teleseismic P- and S-wave arrival times. The natural laboratory is the land areas bordering the North Atlantic; the Scandinavian and East Greenland Caledonides and the Northern...... improved resolution when stations follow profiles. The method was tested on the SCANLIPS array across the Scandinavian Peninsula (Paper I). On the data side, I performed a complete reorganization of the in-house MATLAB-based system (Medhus et al., 2012a,b) for handling event extraction, filtering, cross....../VS put important constraints on the required compositional differences in mantle lithosphere and asthenosphere in the region. Second study focused on the Scandinavian Caledonides, using a dense network south of Trondheim (including SCANLIPS profile) and more sparse station coverage to the north. The UMVB...

  20. Theory of edge states in a quantum anomalous Hall insulator/spin-singlet s-wave superconductor hybrid system

    Science.gov (United States)

    Ii, Akihiro; Yada, Keiji; Sato, Masatoshi; Tanaka, Yukio

    2011-06-01

    We study the edge states for a quantum anomalous Hall system (QAHS) coupled with a spin-singlet s-wave superconductor through the proximity effect, and clarify the topological nature of them. When we consider a superconducting pair potential induced in the QAHS, there appear topological phases with nonzero Chern numbers, i.e., N=1 and N=2, where Andreev bound states appear as chiral Majorana edge modes. We calculate the energy spectrum of the edge modes and the resulting local density of states. It is found that the degenerate chiral Majorana edge modes for N=2 are lifted off by applying a Zeeman magnetic field parallel to the interface or the shift of the chemical potential by doping. The degeneracy of the chiral Majorana edge modes and its lifting are explained by two different winding numbers defined at the time-reversal invariant point of the edge momentum.

  1. Hairs of discrete symmetries and gravity

    Directory of Open Access Journals (Sweden)

    Kang Sin Choi

    2017-06-01

    Full Text Available Gauge symmetries are known to be respected by gravity because gauge charges carry flux lines, but global charges do not carry flux lines and are not conserved by gravitational interaction. For discrete symmetries, they are spontaneously broken in the Universe, forming domain walls. Since the realization of discrete symmetries in the Universe must involve the vacuum expectation values of Higgs fields, a string-like configuration (hair at the intersection of domain walls in the Higgs vacua can be realized. Therefore, we argue that discrete charges are also respected by gravity.

  2. Nonanomalous discrete R symmetry decrees three generations.

    Science.gov (United States)

    Evans, Jason L; Ibe, Masahiro; Kehayias, John; Yanagida, Tsutomu T

    2012-11-02

    We show that more than two generations of quarks and leptons are required to have an anomaly free discrete R symmetry larger than R parity, provided that the supersymmetric standard model can be minimally embedded into a grand unified theory. This connects an explanation for the number of generations with seemingly unrelated problems such as supersymmetry breaking, proton decay, the μ problem, and the cosmological constant through a discrete R symmetry. We also show that three generations is uniquely required by a nonanomalous discrete R symmetry in classes of grand unified theories such as the ones based on (semi)simple gauge groups.

  3. Model for chiral symmetry breaking in QCD

    Energy Technology Data Exchange (ETDEWEB)

    Govaerts, J.; Weyers, J.; Mandula, J.E.

    1984-04-30

    A recently proposed model for dynamical breaking of chiral symmetry in QCD is extended and developed for the calculation of pion and chiral symmetry breaking parameters. The pion is explicitly realized as a massless Goldstone boson and as a bound state of the constituent quarks. We compute, in the limit of exact chiral symmetry, Msub(Q), the constituent quark mass, fsub(..pi..), the pion decay coupling, , the constituent quark loop density, ..mu..sub(..pi..)/sup 2//msub(q), the ratio of the Goldstone boson mass squared to the bare quark mass, and sub(..pi..), the pion electromagnetic charge radius squared.

  4. Symmetry in Image Registration and Deformation Modeling

    DEFF Research Database (Denmark)

    Sommer, Stefan; Jacobs, Henry O.

    We survey the role of symmetry in diffeomorphic registration of landmarks, curves, surfaces, images and higher-order data. The infinite dimensional problem of finding correspondences between objects can for a range of concrete data types be reduced resulting in compact representations of shape...... and spatial structure. This reduction is possible because the available data is incomplete in encoding the full deformation model. Using reduction by symmetry, we describe the reduced models in a common theoretical framework that draws on links between the registration problem and geometric mechanics...... problem. We outline these constructions and further cases where reduction by symmetry promises new approaches to registration of complex data types....

  5. 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.

  6. Exploring Symmetry to Assist Alzheimer's Disease Diagnosis

    Science.gov (United States)

    Illán, I. A.; Górriz, J. M.; Ramírez, J.; Salas-Gonzalez, D.; López, M.; Padilla, P.; Chaves, R.; Segovia, F.; Puntonet, C. G.

    Alzheimer's disease (AD) is a progressive neurodegenerative disorder first affecting memory functions and then gradually affecting all cognitive functions with behavioral impairments and eventually causing death. Functional brain imaging as Single-Photon Emission Computed Tomography (SPECT) is commonly used to guide the clinician's diagnosis. The essential left-right symmetry of human brains is shown to play a key role in coding and recognition. In the present work we explore the implications of this symmetry in AD diagnosis, showing that recognition may be enhanced when considering this latent symmetry.

  7. Hairs of discrete symmetries and gravity

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kang Sin [Scranton Honors Program, Ewha Womans University, Seodaemun-Gu, Seoul 03760 (Korea, Republic of); Center for Fields, Gravity and Strings, CTPU, Institute for Basic Sciences, Yuseong-Gu, Daejeon 34047 (Korea, Republic of); Kim, Jihn E., E-mail: jihnekim@gmail.com [Department of Physics, Kyung Hee University, 26 Gyungheedaero, Dongdaemun-Gu, Seoul 02447 (Korea, Republic of); Center for Axion and Precision Physics Research (IBS), 291 Daehakro, Yuseong-Gu, Daejeon 34141 (Korea, Republic of); Kyae, Bumseok [Department of Physics, Pusan National University, 2 Busandaehakro-63-Gil, Geumjeong-Gu, Busan 46241 (Korea, Republic of); Nam, Soonkeon [Department of Physics, Kyung Hee University, 26 Gyungheedaero, Dongdaemun-Gu, Seoul 02447 (Korea, Republic of)

    2017-06-10

    Gauge symmetries are known to be respected by gravity because gauge charges carry flux lines, but global charges do not carry flux lines and are not conserved by gravitational interaction. For discrete symmetries, they are spontaneously broken in the Universe, forming domain walls. Since the realization of discrete symmetries in the Universe must involve the vacuum expectation values of Higgs fields, a string-like configuration (hair) at the intersection of domain walls in the Higgs vacua can be realized. Therefore, we argue that discrete charges are also respected by gravity.

  8. Constraints on leptogenesis from a symmetry viewpoint

    CERN Document Server

    Felipe, R Gonzalez

    2009-01-01

    It is shown that type-I seesaw models based on the Standard Model Lagrangian extended with three heavy Majorana right-handed fields do not have leptogenesis in leading order, if the symmetries of mass matrices are also the residual symmetry of the Lagrangian. In particular, flavor models that lead to a mass-independent leptonic mixing have a vanishing leptogenesis CP-asymmetry. Based on symmetry arguments, we prove that in these models the Dirac-neutrino Yukawa coupling combinations relevant for leptogenesis are always real in the physical basis where the charged leptons and heavy Majorana neutrinos are diagonal.

  9. Particle-Dependent Deformations of Lorentz Symmetry

    Directory of Open Access Journals (Sweden)

    Giovanni Amelino-Camelia

    2012-07-01

    Full Text Available I report results suggesting that it is possible to introduce laws of relativistic kinematics endowing different types of particles with suitably different deformed-Lorentz-symmetry properties. I also consider some possible applications of these results, among which I highlight those relevant for addressing a long-standing challenge in the description of composite particles, such as atoms, within quantum-gravity-inspired scenarios with Planck-scale deformations of Lorentz symmetry. Some of the new elements here introduced in the formulation of relativistic kinematics appear to also provide the starting point for the development of a correspondingly novel mathematical formulation of spacetime-symmetry algebras.

  10. Gauge origin of discrete flavor symmetries in heterotic orbifolds

    Directory of Open Access Journals (Sweden)

    Florian Beye

    2014-09-01

    Full Text Available We show that non-Abelian discrete symmetries in orbifold string models have a gauge origin. This can be understood when looking at the vicinity of a symmetry enhanced point in moduli space. At such an enhanced point, orbifold fixed points are characterized by an enhanced gauge symmetry. This gauge symmetry can be broken to a discrete subgroup by a nontrivial vacuum expectation value of the Kähler modulus T. Using this mechanism it is shown that the Δ(54 non-Abelian discrete symmetry group originates from a SU(3 gauge symmetry, whereas the D4 symmetry group is obtained from a SU(2 gauge symmetry.

  11. Degree 16 model of S-wave heterogeneity in the upper mantle determined by the Direct Solution Method

    Science.gov (United States)

    Hara, T.

    2001-12-01

    We determine degree 16 model of S-wave heterogeneity in the upper mantle by waveform inversion of long period surface wave data. We use the Direct Solution Method (DSM. Hara et al., [1991]) for theoretical calculations. Although the high accuracy of the DSM can improve the accuracy of earth models (Hara and Geller [2000]), the resolution of the model is still limited due to its heavy computational requirements (e.g., Hara and Geller [2000] obtained an degree 8 model of the upper mantle S-wave velocity). It is necessary to improve the DSM computational efficiency to raise the model resolution. Recently, Hara [2000] implemented the DSM codes on vector-parallel supercomputer to find that the improvement of_@computational efficiency is almost proportional to the number of processing elements. In the present study, we apply these codes to analyses of surface wave data in the frequency band 2-4mHz. The upper mantle is divided into three layers (11-216 km, 216-421 km, and 421-671 km), and the lateral heterogeneity is expanded using spherical harmonics up to degree 16. Long wavelength features of this new model are similar to the model of Hara and Geller [2000]. There is a good correlation between low velocities and hot spot distributions in the shallow upper mantle (11-216 km). There are low velocities in the transition zone under some hot spots (e.g., south Pacific), which suggests that it is possible to trace temperature and/or chemical heterogeneities related to hot spots by surface wave studies.

  12. Symmetry and models of single-walled TiO2 nanotubes with rectangular morphology

    Science.gov (United States)

    Evarestov, Robert A.; Zhukovskii, Yuri F.; Bandura, Andrei V.; Piskunov, Sergei

    2011-04-01

    The formalism of line symmetry groups for one-periodic (1D) nanostructures with rotohelical symmetry has been applied for symmetry analysis of single-walled titania nanotubes (SW TiO2 NTs) formed by rolling up the stoichiometric two-periodic (2D) slabs of anatase structure. Either six- or twelve-layer (101) slabs have been cut from TiO2 crystal in a stable anatase phase. After structural optimization, the latter keeps the centered rectangular symmetry of initial slab slightly compressed along a direction coincided with large sides of elemental rectangles. We have considered two sets of SW TiO2 NTs with optimized six- and twelve-layer structures, which possess chiralities (- n, n) and ( n, n) of anatase nanotubes. To analyze the structural and electronic properties of titania slabs and nanotubes, we have performed their ab initio LCAO calculations, using the hybrid Hartree-Fock/Kohn-Sham exchange-correlation functional PBE0. The band gaps (Δ ɛ gap ) and strain energies ( E strain ) of six-layer nanotubes have been computed and analyzed as functions of NT diameter ( D NT). As to models of 12-layer SW TiO2 NTs of both chiralities, their optimization results in structural exfoliation, i.e., the multi-walled structure should be rather formed in nanotubes with such a number of atomic layers.

  13. Appropriate conditions to realize a p -wave superfluid state starting from a spin-orbit-coupled s -wave superfluid Fermi gas

    Science.gov (United States)

    Yamaguchi, T.; Inotani, D.; Ohashi, Y.

    2017-05-01

    We theoretically investigate a spin-orbit-coupled s -wave superfluid Fermi gas, to examine the time evolution of the system, after an s -wave pairing interaction is replaced by a p -wave one at t =0 . In our recent paper [T. Yamaguchi, D. Inotani, and Y. Ohashi, J. Phys. Soc. Jpn. 86, 013001 (2017), 10.7566/JPSJ.86.013001], we proposed that this manipulation may realize a p -wave superfluid Fermi gas because the p -wave pair amplitude that is induced in the s -wave superfluid state by a parity-broken antisymmetric spin-orbit interaction gives a nonvanishing p -wave superfluid order parameter, immediately after the p -wave interaction is turned on. In this paper, using a time-dependent Bogoliubov-de Gennes theory, we assess this idea under various conditions with respect to the s -wave and p -wave interaction strengths, as well as the spin-orbit coupling strength. From these, we clarify that the momentum distribution of Fermi atoms in the initial s -wave state (t gas physics, our results may provide a possible way to accomplish this.

  14. S-wave velocity structure and tectonic implications of the northwestern sub-basin and Macclesfield of the South China Sea

    Science.gov (United States)

    Wei, Xiaodong; Ruan, Aiguo; Li, Jiabiao; Niu, Xiongwei; Wu, Zhenli; Ding, Weiwei

    2017-06-01

    Based on the optimum P-wave model, the S-wave velocity structure of a wide angle seismic profile (OBS2006-1), across the northwestern sub-basin (NWSB) and the Macclesfield, is simulated by a 2-D ray-tracing method. The results indicate the S-wave velocities in the upper and lower crust of the NWSB are 3.2-3.6 km/s and 3.6-4.0 km/s, with Vp/ Vs ratios of 1.82-1.88 and 1.74-1.82, respectively, which reflect typical oceanic crust characteristics. The S-wave velocity in the upper crust of the NWSB is a little higher in the NNW segment than that in the SSE segment, while the lateral variation of Vp/ Vs ratio is in the opposite. We suggest that the NWSB might have experienced asymmetrical magma flows during sea floor spreading, which may have blurred the magnetic anomaly lineation. The comparison of S-wave velocities along the northern margin of the SCS shows that the west section is different from the east section, and the northwestern margin has a non-volcanic crust structure. The S-wave structures and P-wave velocity models along the northern margin, Macclesfield and Reed Bank show that the Macclesfield might have a conjugate relationship with the Reed Bank.

  15. Topologically Protected Defect States in Open Photonic Systems with Non-Hermitian Charge-Conjugation and Parity-Time Symmetry.

    Science.gov (United States)

    Malzard, Simon; Poli, Charles; Schomerus, Henning

    2015-11-13

    We show that topologically protected defect states can exist in open (leaky or lossy) systems even when these systems are topologically trivial in the closed limit. The states appear from within the continuum, thus in the absence of a band gap, and are generated via exceptional points (a spectral transition that occurs in open wave and quantum systems with a generalized time-reversal symmetry), or via a degeneracy induced by charge-conjugation symmetry (which is related to the pole transition of Majorana zero modes). We demonstrate these findings for a leaking passive coupled-resonator optical waveguide with asymmmetric internal scattering, where the required symmetries (non-Hermitian versions of time-reversal symmetry, chirality, and charge conjugation) emerge dynamically.

  16. The fermion dynamical symmetry model

    Energy Technology Data Exchange (ETDEWEB)

    Cheng-Li Wu [Chung Yuan Christian Univ., Taiwan (China)]|[Holifield Heavy Ion Accelerator, Oak Ridge, TN (United States); Da Hsuan Feng [Drexel Univ., Philadelphia, PA (United States); Guidry, M. [Univ. of Tennessee, Knoxville, TN (United States)]|[Oak Ridge National Lab., TN (United States)

    1994-12-31

    The bulk of contemporary research in nuclear structure physics deals with nuclei that are at least moderately collective in their low-lying states. These are usually well removed from closed shells and constitute a difficult theoretical problem. The most successful descriptions of such nuclei have neglected the many-body nature of the problem, replacing it instead with some form of single-particle field, often deformed, always violating fundamental symmetries that must be restored through projection. Such approaches allow calculations that otherwise would have been impossible, and have been central to the rapid advance in quantitative descriptions of nuclear structure. But in many-body systems, two is more than one and one, and nuclear physics cannot be reduced to a sum of single-particle contributions. The success of mean-field solutions to what is demonstrably a many-body problem has been bought at a price: The quantitative achievements of these methods are dependent on empirical recipes such as the Strutinsky shell correction or the use of phenomenological reference bands in the cranked shell model. Such recipes are clever and successful; they are not without microscopic justification, but in the final analysis they remain recipes, not microscopic theories. It is obviously desirable to construct a theory of nuclear structure that views the nucleus as a correlated many-body system, rather than approximating it by a mean field. In this chapter we wish to present a new approach that aspires to a description of collective nuclei in such terms. Let us provide a rationale for this development by reviewing briefly the history of the nuclear many-body problem.

  17. Time-reversal symmetry breaking in the noncentrosymmetric superconductor Re6Hf : Further evidence for unconventional behavior in the α -Mn family of materials

    Science.gov (United States)

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

    2017-11-01

    The discovery of new families of unconventional superconductors is important both experimentally and theoretically, especially if it challenges current models and thinking. By using muon spin relaxation in zero field, time-reversal symmetry breaking has been observed in Re6Hf . Moreover, the temperature dependence of the superfluid density exhibits s -wave superconductivity with an enhanced electron-phonon coupling. This, coupled with the results from isostructural Re6Zr , shows that the Re6X family is indeed a new and important group of unconventional superconductors.

  18. Will Science and Consciousness Ever Meat? Complexity, Symmetry and Qualia

    Directory of Open Access Journals (Sweden)

    Roger Vergauwen

    2010-06-01

    Full Text Available Within recent discussions in the Philosophy of Mind, the nature of conscious phenomenal states or qualia (also called ‘raw feels’ or the feel of ‘what it is like to be’ has been an important focus of interest. Proponents of Mind-Body Type-Identity theories have claimed that mental states can be reduced to neurophysiological states of the brain. Others have denied that such a reduction is possible; for them, there remains an explanatory gap. In this paper, functionalist, physicalist, epiphenomenalist, and biological models of the mind are discussed and compared. Donald Davidson’s Anomalous Monism is proposed as a unifying framework for a non-reductive theory of qualia and consciousness. Downward Causation, Emergence through Symmetry-breaking, and Dynamical Systems Theory are used to show how consciousness and qualia emerge from their neural substrate and can also be causally efficacious.

  19. Bottom-up discrete symmetries for Cabibbo mixing

    Energy Technology Data Exchange (ETDEWEB)

    De Medeiros Varzielas, Ivo [Southampton Univ. (United Kingdom). School of Physics and Astronomy; Rasmussen, Rasmus W. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Talbert, Jim [Oxford Univ. (United Kingdom). Rudolf Peierls Centre for Theoretical Physics

    2016-05-15

    We perform a bottom-up search for discrete non-Abelian symmetries capable of quantizing the Cabibbo angle that parameterizes CKM mixing. Given a particular Abelian symmetry structure in the up and down sectors, we construct representations of the associated residual generators which explicitly depend on the degrees of freedom present in our effective mixing matrix. We then discretize those degrees of freedom and utilize the Groups, Algorithms, Programming (GAP) package to close the associated finite groups. This short study is performed in the context of recent results indicating that, without resorting to special model-dependent corrections, no small-order finite group can simultaneously predict all four parameters of the three-generation CKM matrix and that only groups of O(10{sup 2}) can predict the analogous parameters of the leptonic PMNS matrix, regardless of whether neutrinos are Dirac or Majorana particles. Therefore a natural model of flavour might instead incorporate small(er) finite groups whose predictions for fermionic mixing are corrected via other mechanisms.

  20. New symmetries for the gravitational S-matrix

    Energy Technology Data Exchange (ETDEWEB)

    Campiglia, Miguel [Instituto de Física, Facultad de Ciencias,Montevideo 11400 (Uruguay); Laddha, Alok [Chennai Mathematical Institute,Siruseri 603103 (India)

    2015-04-15

    In http://dx.doi.org/10.1103/PhysRevD.90.124028 we proposed a generalization of the BMS group G which is a semi-direct product of supertranslations and smooth diffeomorphisms of the conformal sphere. Although an extension of BMS, G is a symmetry group of asymptotically flat space times. By taking G as a candidate symmetry group of the quantum gravity S-matrix, we argued that the Ward identities associated to the generators of Diff(S{sup 2}) were equivalent to the Cachazo-Strominger subleading soft graviton theorem. Our argument however was based on a proposed definition of the Diff(S{sup 2}) charges which we could not derive from first principles as G does not have a well defined action on the radiative phase space of gravity. Here we fill this gap and provide a first principles derivation of the Diff(S{sup 2}) charges. The result of this paper, in conjunction with the results of http://arxiv.org/abs/1401.7026http://dx.doi.org/10.1103/PhysRevD.90.124028 prove that the leading and subleading soft theorems are equivalent to the Ward identities associated to G.

  1. Student understanding of Symmetry and Gauss' law

    CERN Document Server

    Singh, Chandralekha

    2016-01-01

    Helping students learn why Gauss' law can or cannot be easily applied to determine the strength of the electric field at various points for a particular charge distribution, and then helping them learn to determine the shape of the Gaussian surfaces if sufficient symmetry exists can develop their reasoning and problem solving skills. We investigate the difficulties that students in calculus-based introductory physics courses have with the concepts of symmetry, electric field and electric flux that are pivotal to Gauss' law of electricity. Determination of the electric field using Gauss' law requires discerning the symmetry of a particular charge distribution and being able to predict the direction of the electric field everywhere if a high symmetry exists. It requires a good grasp of how to add the electric field vectors using the principle of superposition, and the concepts of area vector and electric flux. We administered free response and multiple-choice questions and conducted interviews with individual s...

  2. Nobel Prize for work on broken symmetries

    CERN Multimedia

    2008-01-01

    The 2008 Nobel Prize for Physics goes to three physicists who have worked on broken symmetries in particle physics. The announcement of the 2008 Nobel Prize for physics was transmitted to the Globe of Science and Innovation via webcast on the occasion of the preview of the Nobel Accelerator exhibition.On 7 October it was announced that the Royal Swedish Academy of Sciences had awarded the 2008 Nobel Prize for physics to three particle physicists for their fundamental work on the mechanisms of broken symmetries. Half the prize was awarded to Yoichiro Nambu of Fermilab for "the discovery of the mechanism of spontaneous broken symmetry in subatomic physics". The other half is shared by Makato Kobayashi of Japan’s KEK Institute and Toshihide Maskawa of the Yukawa Institute at the University of Kyoto "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in Nature". At th...

  3. R parity violation from discrete R symmetries

    Directory of Open Access Journals (Sweden)

    Mu-Chun Chen

    2015-02-01

    Full Text Available We consider supersymmetric extensions of the standard model in which the usual R or matter parity gets replaced by another R or non-R discrete symmetry that explains the observed longevity of the nucleon and solves the μ problem of MSSM. In order to identify suitable symmetries, we develop a novel method of deriving the maximal ZN(R symmetry that satisfies a given set of constraints. We identify R parity violating (RPV and conserving models that are consistent with precision gauge unification and also comment on their compatibility with a unified gauge symmetry such as the Pati–Salam group. Finally, we provide a counter-example to the statement found in the recent literature that the lepton number violating RPV scenarios must have μ term and the bilinear κLHu operator of comparable magnitude.

  4. Centre vortex removal restores chiral symmetry

    Science.gov (United States)

    Trewartha, Daniel; Kamleh, Waseem; Leinweber, Derek B.

    2017-12-01

    The influence of centre vortices on dynamical chiral symmetry breaking is investigated through the light hadron spectrum on the lattice. Recent studies of the quark propagator and other quantities have provided evidence that centre vortices are the fundamental objects underpinning dynamical chiral symmetry breaking in {SU}(3) gauge theory. For the first time, we use the chiral overlap fermion action to study the low-lying hadron spectrum on lattice ensembles consisting of Monte Carlo, vortex-removed, and vortex-projected gauge fields. We find that gauge field configurations consisting solely of smoothed centre vortices are capable of reproducing all the salient features of the hadron spectrum, including dynamical chiral symmetry breaking. The hadron spectrum on vortex-removed fields shows clear signals of chiral symmetry restoration at light values of the bare quark mass, while at heavy masses the spectrum is consistent with a theory of weakly interacting constituent quarks.

  5. Symmetry and the Cosmic Microwave Background

    Science.gov (United States)

    Wollock, Edward J.

    2012-01-01

    A brief historical introduction to the development of observational astronomy and cosmology will be presented. The close relationship between the properties of light, symmetry, and our understanding the contents of our universe will be explored.

  6. Deconfined quantum critical points: symmetries and dualities

    Science.gov (United States)

    Wang, Chong; Nahum, Adam; Metlitski, Max; Xu, Cenke; Senthil, T.

    The deconfined quantum critical point (QCP) between the Neel and the valence bond solid (VBS) phases was proposed as an example of (2 + 1) d conformal field theories that are fundamentally different from all the standard Landau-Ginzburg-Wilson-Fisher fixed points. In this work we demonstrate that the deconfined QCP, both the easy-plane version and the version with an explicit SU(2) spin symmetry, have multiple equivalent descriptions. In particular, the easy-plane deconfined QCP, besides its self-duality that was discussed before, is also dual to the Nf = 2 fermionic quantum electrodynamics (QED), which has its own self-duality and hence has an O(4) ×Z2T symmetry; the deconfined QCP with the explicit SU(2) spin symmetry is dual to the Nf = 2 QED-Gross-Neveu fixed point, and could have an emergent SO(5) symmetry, as was conjectured before.

  7. Fractals and Hidden Symmetries in DNA

    Directory of Open Access Journals (Sweden)

    Carlo Cattani

    2010-01-01

    complex representation, together with the corresponding walks on DNA; in particular, it is shown that DNA walks are fractals. Finally, by using the wavelet analysis, the existence of symmetries is proven.

  8. Nonlinear (super)symmetries and amplitudes

    Energy Technology Data Exchange (ETDEWEB)

    Kallosh, Renata [Physics Department, Stanford University,382 Via Pueblo Mall, Stanford, CA 94305-4060 (United States)

    2017-03-07

    There is an increasing interest in nonlinear supersymmetries in cosmological model building. Independently, elegant expressions for the all-tree amplitudes in models with nonlinear symmetries, like D3 brane Dirac-Born-Infeld-Volkov-Akulov theory, were recently discovered. Using the generalized background field method we show how, in general, nonlinear symmetries of the action, bosonic and fermionic, constrain amplitudes beyond soft limits. The same identities control, for example, bosonic E{sub 7(7)} scalar sector symmetries as well as the fermionic goldstino symmetries. We present a universal derivation of the vanishing amplitudes in the single (bosonic or fermionic) soft limit. We explain why, universally, the double-soft limit probes the coset space algebra. We also provide identities describing the multiple-soft limit. We discuss loop corrections to N≥5 supergravity, to the D3 brane, and the UV completion of constrained multiplets in string theory.

  9. Symmetry energy of warm nuclear systems

    Energy Technology Data Exchange (ETDEWEB)

    Agrawal, B.K.; De, J.N.; Samaddar, S.K. [Saha Institute of Nuclear Physics, Kolkata (India); Centelles, M.; Vinas, X. [Universitat de Barcelona, Departament d' Estructura i Constituents de la Materia, Facultat de Fisica, and Institut de Ciencies del Cosmos, Barcelona (Spain)

    2014-02-15

    The temperature dependence of the symmetry energy and symmetry free energy coefficients of infinite nuclear matter and of finite nuclei is investigated. For infinite matter, both these coefficients are found to have a weaker dependence on temperature at densities close to saturation; at low but homogeneous densities, the temperature dependence becomes stronger. For finite systems, different definitions of symmetry energy coefficients are encountered in the literature yielding different values. A resolution to this problem is suggested from a global liquid-drop-inspired fit of the energies and free energies of a host of nuclei covering the entire periodic table. The hot nucleus is modeled in a subtracted finite-temperature Thomas-Fermi framework, with dynamical surface phonon coupling to nucleonic motion plugged in. Contrary to infinite nuclear matter, a substantial change in the symmetry energy coefficients is observed for finite nuclei with temperature. (orig.)

  10. Symmetry and group theory throughout physics

    Directory of Open Access Journals (Sweden)

    Villain J.

    2012-03-01

    Full Text Available As noticed in 1884 by Pierre Curie [1], physical properties of matter are tightly related to the kind of symmetry of the medium. Group theory is a systematic tool, though not always easy to handle, to exploit symmetry properties, for instance to find the eigenvectors and eigenvalues of an operator. Certain properties (optical activity, piezoelectricity are forbidden in molecules or crystals of high symmetry. A few theorems (Noether, Goldstone establish general relations between physical properties and symmetry. Applications of group theory to condensed matter physics, elementary particle physics, quantum mechanics, electromagnetism are reviewed. Group theory is not only a tool, but also a beautiful construction which casts insight into natural phenomena.

  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. Teaching symmetry in the introductory physics curriculum

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Christopher T.; Lederman, Leon M.

    2000-01-01

    Modern physics is largely defined by fundamental symmetry principles and Noether's Theorem. Yet these are not taught, or rarely mentioned, to beginning students, thus missing an opportunity to reveal that the subject of physics is as lively and contemporary as molecular biology, and as beautiful as the arts. We prescribe a symmetry module to insert into the curriculum, of a week's length.

  13. Symmetry processing in Nafsat al-Masdur

    Directory of Open Access Journals (Sweden)

    Aliakbar Samkhaniani

    2016-06-01

    B: Co-ornament: the second kind of rhetorical symmetry processing is co-ornament and co-ornament is so that the author or poet applies similar ornaments in two phrases or two hemistich or two verses. If co-ornament is particularly well balanced formed, i.e. every ornament is in a well-balanced status with its symmetry, shows the capabilities and skills of its creator.

  14. Reverse-symmetry waveguides: Theory and fabrication

    DEFF Research Database (Denmark)

    Horvath, R.; Lindvold, Lars René; Larsen, N.B.

    2002-01-01

    We present an extensive theoretical analysis of reverse-symmetry waveguides with special focus on their potential application as sensor components in aqueous media and demonstrate a novel method for fabrication of such waveguides. The principle of reverse symmetry is based on making the refractiv...... has the advantage of deeper penetration of the evanescent electromagnetic field into the cover medium, theoretically permitting higher sensitivity to analytes compared to traditional waveguide designs. We present calculated sensitivities and probing depths of conventional and reverse...

  15. On some Symmetry Axioms in Relativity Theories

    CERN Document Server

    Székely, Gergely

    2016-01-01

    In this paper we review two symmetry axioms of special relativity and their connections to each other together with their role in some famous predictions of relativity theory, such as time dilation, length contraction, and the twin paradox. We also discuss briefly counterparts of these symmetry axioms in general relativity and formulate a conjecture, namely that without them the axioms of general relativity would capture general relativistic spacetimes only up to conformal equivalence.

  16. Noether symmetries in the phase space

    Directory of Open Access Journals (Sweden)

    Bogar Díaz

    2014-09-01

    Full Text Available The constants of motion of a mechanical system with a finite number of degrees of freedom are related to the variational symmetries of a Lagrangian constructed from the Hamiltonian of the original system. The configuration space for this Lagrangian is the phase space of the original system. The symmetries considered in this manner include transformations of the time and may not be canonical in the standard sense.

  17. The central role of symmetry in physics

    CERN Document Server

    Das, Saurya

    2016-01-01

    Spacetime and internal symmetries can be used to severely restrict the form of the equations for the fundamental laws of physics. The success of this approach in the context of general relativity and particle physics motivates the conjecture that symmetries may help us to one day uncover the ultimate theory that provides a unique, unified description of all observed physical phenomena. We examine some of the strengths and weaknesses of this conjecture.

  18. Relabeling symmetries in hydrodynamics and magnetohydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Padhye, N.; Morrison, P.J.

    1996-04-01

    Lagrangian symmetries and concomitant generalized Bianchi identities associated with the relabeling of fluid elements are found for hydrodynamics and magnetohydrodynamics (MHD). In hydrodynamics relabeling results in Ertel`s theorem of conservation of potential vorticity, while in MHD it yields the conservation of cross helicity. The symmetries of the reduction from Lagrangian (material) to Eulerian variables are used to construct the Casimir invariants of the Hamiltonian formalism.

  19. Continuous point symmetries in Group Field Theories

    CERN Document Server

    Kegeles, Alexander

    2016-01-01

    We discuss the notion of symmetries in non-local field theories characterized by integro-differential equation of motion, from a geometric perspective. We then focus on Group Field Theory (GFT) models of quantum gravity. We provide a general analysis of their continuous point symmetry transformations, including the generalized conservation laws following from them, and apply it to several GFT models of interest to current research.

  20. Microscopic Symmetry Imposed by Rotational Symmetry Boundary Conditions in Molecular Dynamics Simulation

    Science.gov (United States)

    Roy, Amitava; Post, Carol Beth

    2011-01-01

    A large number of viral capsids, as well as other macromolecular assemblies, have icosahedral structure or structures with other rotational symmetries. This symmetry can be exploited during molecular dynamics (MD) to model in effect the full viral capsid using only a subset of primary atoms plus copies of image atoms generated from rotational symmetry boundary conditions (RSBC). A pure rotational symmetry operation results in both primary and image atoms at short range, and within nonbonded interaction distance of each other, so that nonbonded interactions can not be specified by the minimum image convention and explicit treatment of image atoms is required. As such an unavoidable consequence of RSBC is that the enumeration of nonbonded interactions in regions surrounding certain rotational axes must include both a primary atom and its copied image atom, thereby imposing microscopic symmetry for some forces. We examined the possibility of artifacts arising from this imposed microscopic symmetry of RSBC using two simulation systems: a water shell and human rhinovirus 14 (HRV14) capsid with explicit water. The primary unit was a pentamer of the icosahedron, which has the advantage of direct comparison of icosahedrally equivalent spatial regions, for example regions near a 2-fold symmetry axis with imposed symmetry and a 2-fold axis without imposed symmetry. Analysis of structural and dynamic properties of water molecules and protein atoms found similar behavior near symmetry axes with imposed symmetry and where the minimum image convention fails compared with that in other regions in the simulation system, even though an excluded volume effect was detected for water molecules near the axes with imposed symmetry. These results validate the use of RSBC for icosahedral viral capsids or other rotationally symmetric systems. PMID:22096451

  1. Optical Dark-Field and Electron Energy Loss Imaging and Spectroscopy of Symmetry-Forbidden Modes in Loaded Nanogap Antennas.

    Science.gov (United States)

    Brintlinger, Todd; Herzing, Andrew A; Long, James P; Vurgaftman, Igor; Stroud, Rhonda; Simpkins, B S

    2015-06-23

    We have produced large numbers of hybrid metal-semiconductor nanogap antennas using a scalable electrochemical approach and systematically characterized the spectral and spatial character of their plasmonic modes with optical dark-field scattering, electron energy loss spectroscopy with principal component analysis, and full wave simulations. The coordination of these techniques reveal that these nanostructures support degenerate transverse modes which split due to substrate interactions, a longitudinal mode which scales with antenna length, and a symmetry-forbidden gap-localized transverse mode. This gap-localized transverse mode arises from mode splitting of transverse resonances supported on both antenna arms and is confined to the gap load enabling (i) delivery of substantial energy to the gap material and (ii) the possibility of tuning the antenna resonance via active modulation of the gap material's optical properties. The resonant position of this symmetry-forbidden mode is sensitive to gap size, dielectric strength of the gap material, and is highly suppressed in air-gapped structures which may explain its absence from the literature to date. Understanding the complex modal structure supported on hybrid nanosystems is necessary to enable the multifunctional components many seek.

  2. Gait Symmetry in Children with Autism

    Directory of Open Access Journals (Sweden)

    Victoria L. Chester

    2012-01-01

    Full Text Available Most studies examining gait asymmetry have focused on infants and toddlers and have tended to use subjective methods of evaluating movement. No previous studies have examined gait symmetry in older children with autism using objective motion capture systems. The purpose of this paper was to quantify gait symmetry in children with autism versus age-matched controls. Fourteen children with autism (N=14 and twenty-two (N=22 age, height, and weight-matched controls participated in the study. An eight camera Vicon motion capture system and four Kistler force plates were used to compute temporal-spatial parameters and symmetry indices during walking. Group differences in these measures were tested using MANOVAs. No significant differences between the autism and control group were found for any of the temporal-spatial measures or symmetry indices. Therefore, results suggest that children with autism demonstrate typical symmetry or interlimb movement during gait. Further research is needed to examine the use of different gait inputs to the symmetry indices (e.g., joint angles and moments. A greater awareness of the movement patterns associated with autism may increase our understanding of this disorder and have important implications for treatment planning.

  3. Effect of hydrogenation on the band gap of graphene nano-flakes

    Energy Technology Data Exchange (ETDEWEB)

    Tachikawa, Hiroto, E-mail: hiroto@eng.hokudai.ac.jp; Iyama, Tetsuji; Kawabata, Hiroshi

    2014-03-03

    The effects of hydrogenation on the band gap of graphene have been investigated by means of density functional theory method. It is generally considered that the band gap increases with increasing coverage of hydrogen atom on the graphene. However, the present study shows that the band gap decreases first with increasing hydrogen coverage and reaches the lowest value at finite coverage (γ = 0.3). Next, the band gap increases to that of insulator with coverage from 0.3 to 1.0. This specific feature of the band gap is reasonably explained by broken symmetry model and the decrease of pi-conjugation. The electronic states of hydrogenated graphene are discussed. - Highlights: • Density functional theory calculations were carried out for hydrogen on graphene • Effects of hydrogenation on the band gap of graphene were examined. • The band gap showed a minimum at a finite coverage. • Mechanism of specific band gap feature was discussed.

  4. Spontaneous Symmetry Breaking in Nonrelativistic Systems

    Science.gov (United States)

    Watanabe, Haruki

    The subject of condensed matter physics is very rich --- there are an infinite number of parameters producing a diversity of exciting phenomena. As a theorist, my goal is to distill general principles out of this complexity --- to construct theories that can coherently explain many known examples altogether. This thesis is composed of several attempts to develop such theories in topics related to spontaneously symmetry breaking. A remarkable feature of many-body interacting systems is that although they are described by equations respecting various symmetries, they may spontaneously organize into a state that explicitly breaks symmetries. Examples are numerous: various types of crystalline and magnetic orders, Bose-Einstein condensates of cold atoms, superfluids of liquid helium, chiral symmetry in QCD, neutron stars, and cosmic inflation. These systems with spontaneously broken continuous symmetries have gapless excitations, so called Nambu-Goldstone bosons (NGBs). Although the properties of NGBs are well understood in Lorentz-invariant systems, surprisingly, some basic properties of NGBs such as their number and dispersion in nonrelativistic systems have not been discussed from a general perspective. In the first part of this thesis, we solve this issue by developing and analyzing an effective Lagrangian that coherently captures the low-energy, long-distance physics of many different symmetry-breaking states all at once. Next, we examine whether these NGBs originating from spontaneous symmetry breaking remain to be well-defined excitations inside a metal, where low-energy electrons near Fermi surface can collide with them. Our result is a one equation criterion that specifies whether the interactions between electrons and NGBs can be ignored, or whether it completely changes their character. In the latter case, unusual phases of matter such as non-Fermi liquids may arise; in that case, NGBs are overdamped and cannot form particle-like excitations in spite of the

  5. Gap and density theorems

    CERN Document Server

    Levinson, N

    1940-01-01

    A typical gap theorem of the type discussed in the book deals with a set of exponential functions { \\{e^{{{i\\lambda}_n} x}\\} } on an interval of the real line and explores the conditions under which this set generates the entire L_2 space on this interval. A typical gap theorem deals with functions f on the real line such that many Fourier coefficients of f vanish. The main goal of this book is to investigate relations between density and gap theorems and to study various cases where these theorems hold. The author also shows that density- and gap-type theorems are related to various propertie

  6. Bridging the Gap

    DEFF Research Database (Denmark)

    Kramer Overgaard, Majken; Broeng, Jes; Jensen, Monika Luniewska

    Bridging the Gap (BtG) is a 2-year project funded by The Danish Industry Foundation. The goal of Bridging the Gap has been to create a new innovation model which will increase the rate at which Danish universities can spinout new technology ventures.......Bridging the Gap (BtG) is a 2-year project funded by The Danish Industry Foundation. The goal of Bridging the Gap has been to create a new innovation model which will increase the rate at which Danish universities can spinout new technology ventures....

  7. Perception of Mirror Symmetry in Autism Spectrum Disorders

    Science.gov (United States)

    Falter, Christine M.; Bailey, Anthony J.

    2012-01-01

    Gestalt grouping in autism spectrum disorders (ASD) is selectively impaired for certain organization principles but for not others. Symmetry is a fundamental Gestalt principle characterizing many biological shapes. Sensitivity to symmetry was tested using the Picture Symmetry Test, which requires finding symmetry lines on pictures. Individuals…

  8. Azimuthal Seismic Amplitude Variation with Offset and Azimuth Inversion in Weakly Anisotropic Media with Orthorhombic Symmetry

    Science.gov (United States)

    Pan, Xinpeng; Zhang, Guangzhi; Yin, Xingyao

    2017-10-01

    Seismic amplitude variation with offset and azimuth (AVOaz) inversion is well known as a popular and pragmatic tool utilized to estimate fracture parameters. A single set of vertical fractures aligned along a preferred horizontal direction embedded in a horizontally layered medium can be considered as an effective long-wavelength orthorhombic medium. Estimation of Thomsen's weak-anisotropy (WA) parameters and fracture weaknesses plays an important role in characterizing the orthorhombic anisotropy in a weakly anisotropic medium. Our goal is to demonstrate an orthorhombic anisotropic AVOaz inversion approach to describe the orthorhombic anisotropy utilizing the observable wide-azimuth seismic reflection data in a fractured reservoir with the assumption of orthorhombic symmetry. Combining Thomsen's WA theory and linear-slip model, we first derive a perturbation in stiffness matrix of a weakly anisotropic medium with orthorhombic symmetry under the assumption of small WA parameters and fracture weaknesses. Using the perturbation matrix and scattering function, we then derive an expression for linearized PP-wave reflection coefficient in terms of P- and S-wave moduli, density, Thomsen's WA parameters, and fracture weaknesses in such an orthorhombic medium, which avoids the complicated nonlinear relationship between the orthorhombic anisotropy and azimuthal seismic reflection data. Incorporating azimuthal seismic data and Bayesian inversion theory, the maximum a posteriori solutions of Thomsen's WA parameters and fracture weaknesses in a weakly anisotropic medium with orthorhombic symmetry are reasonably estimated with the constraints of Cauchy a priori probability distribution and smooth initial models of model parameters to enhance the inversion resolution and the nonlinear iteratively reweighted least squares strategy. The synthetic examples containing a moderate noise demonstrate the feasibility of the derived orthorhombic anisotropic AVOaz inversion method, and the

  9. Azimuthal Seismic Amplitude Variation with Offset and Azimuth Inversion in Weakly Anisotropic Media with Orthorhombic Symmetry

    Science.gov (United States)

    Pan, Xinpeng; Zhang, Guangzhi; Yin, Xingyao

    2018-01-01

    Seismic amplitude variation with offset and azimuth (AVOaz) inversion is well known as a popular and pragmatic tool utilized to estimate fracture parameters. A single set of vertical fractures aligned along a preferred horizontal direction embedded in a horizontally layered medium can be considered as an effective long-wavelength orthorhombic medium. Estimation of Thomsen's weak-anisotropy (WA) parameters and fracture weaknesses plays an important role in characterizing the orthorhombic anisotropy in a weakly anisotropic medium. Our goal is to demonstrate an orthorhombic anisotropic AVOaz inversion approach to describe the orthorhombic anisotropy utilizing the observable wide-azimuth seismic reflection data in a fractured reservoir with the assumption of orthorhombic symmetry. Combining Thomsen's WA theory and linear-slip model, we first derive a perturbation in stiffness matrix of a weakly anisotropic medium with orthorhombic symmetry under the assumption of small WA parameters and fracture weaknesses. Using the perturbation matrix and scattering function, we then derive an expression for linearized PP-wave reflection coefficient in terms of P- and S-wave moduli, density, Thomsen's WA parameters, and fracture weaknesses in such an orthorhombic medium, which avoids the complicated nonlinear relationship between the orthorhombic anisotropy and azimuthal seismic reflection data. Incorporating azimuthal seismic data and Bayesian inversion theory, the maximum a posteriori solutions of Thomsen's WA parameters and fracture weaknesses in a weakly anisotropic medium with orthorhombic symmetry are reasonably estimated with the constraints of Cauchy a priori probability distribution and smooth initial models of model parameters to enhance the inversion resolution and the nonlinear iteratively reweighted least squares strategy. The synthetic examples containing a moderate noise demonstrate the feasibility of the derived orthorhombic anisotropic AVOaz inversion method, and the

  10. Substrate-induced band gap opening in epitaxial graphene

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, S.Y.; Gweon, G.-H.; Fedorov, A.V.; First, P.N.; de Heer,W.A.; Lee, D.-H.; Guinea, F.; Castro Neto, A.H.; Lanzara, A.

    2007-09-08

    Graphene has shown great application potential as the hostmaterial for next-generation electronic devices. However, despite itsintriguing properties, one of the biggest hurdles for graphene to beuseful as an electronic material is the lack of an energy gap in itselectronic spectra. This, for example, prevents the use of graphene inmaking transistors. Although several proposals have been made to open agap in graphene's electronic spectra, they all require complexengineering of the graphene layer. Here, we show that when graphene isepitaxially grown on SiC substrate, a gap of ~;0.26 eV is produced. Thisgap decreases as the sample thickness increases and eventually approacheszero when the number of layers exceeds four. We propose that the originof this gap is the breaking of sublattice symmetry owing to thegraphene-substrate interaction. We believe that our results highlight apromising direction for band gap engineering of graphene.

  11. Gapped fermions in top-down holographic superconductors

    Science.gov (United States)

    DeWolfe, Oliver; Gubser, Steven S.; Henriksson, Oscar; Rosen, Christopher

    2017-04-01

    We use holography to compute spectral functions of certain fermionic operators in three different finite-density, zero-temperature states of Aharony-Bergman-Jafferis-Maldacena (ABJM) theory with a broken U (1 ) symmetry. In each of the three states, dual to previously studied domain wall solutions of four-dimensional gauged supergravity, we find that the fermionic operators have gapped spectra. In one case the gap can be traced to the small charge of the fermions, while in the other cases it is due to a particular interaction that mixes particles and holes.

  12. An upper-mantle S-wave velocity model for Northern Europe from Love and Rayleigh group velocities

    Science.gov (United States)

    Weidle, Christian; Maupin, Valérie

    2008-12-01

    A model of upper-mantle S-wave velocity and transverse anisotropy beneath northwestern Europe is presented, based on regional surface wave observations. Group velocities for both Love and Rayleigh surface waves are measured on waveform data from international and regional data archives (including temporary deployments) and then inverted for group velocity maps, using a method accounting for Fresnel zone sensitivity. The group velocity variations are larger than in global reference maps, and we are able to resolve unprecedented details. We then apply a linear inversion scheme to invert for local 1-D shear wave velocity profiles which are consequently assembled to a 3-D model. By choosing conservative regularization parameters in the 2-D inversion, we ensure the smoothness of the group velocity maps and hence of the resulting 3-D shear wave speed model. To account for the different tectonic regimes in the study region and investigate the sensitivity of the 1-D inversions to inaccuracies in crustal parameters, we analyse inversions with different reference models of increasing complexity (pure 1-D, 3-D crust/1-D mantle and pure 3-D). We find that all inverted models are very consistent at depths below 70 km. At shallower depths, the constraints put by the reference models, primarily Moho depth which we do not invert for, remain the main cause for uncertainty in our inversion. The final 3-D model shows large variations in S-wave velocity of up to +/-12 per cent. We image an intriguing low-velocity anomaly in the depth range 70-150 km that extends from the Iceland plume beneath the North Atlantic and in a more than 400 km wide channel under Southern Scandinavia. Beneath Southern Norway, the negative perturbations are around 10 per cent with respect to ak135, and a shallowing of the anomaly is indicated which could be related to the sustained uplift of Southern Scandinavia in Neogene times. Furthermore, our upper-mantle model reveals good alignment to ancient plate

  13. SYMMETRY – MATHEMATICAL CONCEPTS AND APPLICATIONS IN TECHNOLOGY AND ENGINEERING

    Directory of Open Access Journals (Sweden)

    Dobre Daniel

    2009-07-01

    Full Text Available This article discusses the relation between the concept of symmetry and its applications in engineering. "Symmetry" is interpreted in a broad sense as repeated, coplanar shape fragments. An analysis of symmetry, which justifies its applications in engineering is given and discussed. After a brief explication of group theory and symmetry types, we show that there are industrial workpieces where symmetry is omnipresent. The analysis of symmetry can also be utilized for future research concerns the combining symmetry information with other functional characteristic of digital 3D design.

  14. 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 ...

  15. Group Parametrized Tunneling and Local Symmetry Conditions

    Science.gov (United States)

    Harter, William; Mitchell, Justin

    2010-06-01

    Recently, Hougen showed an ad hoc symmetry-based parameterization scheme for analyzing tunneling dynamics and high resolution spectra of fluxional molecular structure similar to S-parameter analysis of superfine structure in SF_6 or NH_3 maser inversion dynamics by Feynman et.al. The problem is that ad hoc parametrization, like path integration in general, can lead to logjams of parameters or ``paths'' with no way to pick out the relevant ones. We show a way to identify and use relevant parameters for a tunneling Hamiltonian H having global G-symmetry-defined bases by first expressing H as a linear combination bar γ ^i {bar g}_i of operators in dual symmetry group bar G. The coefficients bar γ ^i are parameters that define a complete set of allowed paths for any H with G-symmetry and are related thru spectral decomposition of G to eigensolutions of H. Quantum G vs.bar G duality generalizes lab -vs. -body and state -vs. -particle. The number of relevant bar γ ^i-parameters is reduced if a system tends to stick in states of a local symmetry subgroup LsubsetG so the H spectrum forms level clusters labeled by induced representations d(ℓ)(L)\\uparrowG. A cluster-(ℓ) has one E(epsilon)-level labeled by G species (epsilon) for each L species (ℓ) in Depsilon(G)downarrowL by Frobenius reciprocity. Then we apply local symmetry conditions to each irrep Depsilon(bar γ ^i {bar g}_i) that has already been reduced with respect to local symmetry L. This amounts to setting each off-diagonal component Dj,kepsilon(H) to zero. Local symmetry conditions may tell which bar γ ^i-parameters are redundant or zero and directly determine d(ℓ)\\uparrowG tunneling matrix eigenvalues that give E(epsilon)-levels as well as eigenvectors. Otherwise one may need to choose a particular localizing subgroup chain LsubsetL_1subsetL_2...G and further reduce the number of path parameters to facilitate spectral fitting. J.T. Hougen, 2009 MSS RJ01, {J Mol Spect 123, 197 (1987) W.G. Harter and

  16. Bridge the Gap

    DEFF Research Database (Denmark)

    Marselis, Randi Lorenz

    2017-01-01

    This article focuses on photo projects organised for teenage refugees by the Society for Humanistic Photography (Berlin, Germany). These projects, named Bridge the Gap I (2015), and Bridge the Gap II (2016), were carried out in Berlin and brought together teenagers with refugee and German...

  17. Yukawa Textures from Family Symmetry and Unification

    CERN Document Server

    Allanach, Benjamin C; Leontaris, George K; Lola, S

    1997-01-01

    In this letter, we show how the combination of both a gauged U(1)_X family symmetry and an extended vertical gauge symmetry in a single model, allows for the presence of additional Clebsch texture zeroes in the fermion mass matrices. This leads to new structures for the textures, with increased predictivity, as compared to schemes with enhanced family symmetries only. We illustrate these ideas in the context of the Pati-Salam gauge group SU(4)xSU(2)_LxSU(2)_R$ supplemented by a U(1)_X gauged family symmetry. In the case of symmetric mass matrices, two of the solutions of Ramond, Roberts and Ross that may not be obtained by family symmetries only, are accurately reproduced. For non-symmetric textures, new structures arise in models of this type. To distinguish between the solutions in this latter case, we performed a numerical fit to the charged fermion mass and mixing data. The best solution we found allows a fit with a total chi^2 of 0.39, for three degrees of freedom.

  18. Violation of Particle Anti-particle Symmetry

    CERN Multimedia

    CERN. Geneva

    2001-01-01

    Symmetry is a fundamental concept which can be found in the whole range of human activities e. g. from arts to science. The beauty of a statues is often related to its symmetric form. In physics, all the laws are related to some sort of symmetry. Equally important is a small breakdown ofsymmetry. Even for the case of a statue, its beauty might be enhanced by introducing small distortions. In this course, we investigate the role symmetry in the world of elementary particles. Some symmetries found there are very similar to those which can be seen in our daily life, while others are more exotic and related to the quantum nature of the elementary particles. Our particular focus ismade on symmetry and its violation between the matter and anti-matter, known as CP violation. It is experimentally well established that particleand anti-particle behave a tiny bit differently in the world of elementary particles. We discuss how this would be explained and how we can extendour knowledge. Evolution of our universe is stro...

  19. Symmetry in social exchange and health

    Science.gov (United States)

    Siegrist, Johannes

    2005-10-01

    Symmetry is a relevant concept in sociological theories of exchange. It is rooted in the evolutionary old norm of social reciprocity and is particularly important in social contracts. Symmetry breaking through violation of the norm of reciprocity generates strain in micro-social systems and, above all, in victims of non-symmetric exchange. In this contribution, adverse healthconsequences of symmetry breaking in contractual social exchange are analysed, with a main focus on the employment contract. Scientific evidence is derived from prospective epidemiological studies testing the model of effort-reward imbalance at work. Overall, a twofold elevated risk of incident disease is observed in employed men and women who are exposed to non-symmetric exchange. Health risks include coronary heart disease, depression and alcohol dependence, among others. Preliminary results suggest similar effects on health produced by symmetry breaking in other types of social relationships (e.g. partnership, parental roles). These findings underline the importance of symmetry in contractual social exchange for health and well-being.

  20. A method for quantifying rotational symmetry.

    Science.gov (United States)

    Frey, Frank M; Robertson, Aaron; Bukoski, Michael

    2007-01-01

    Here, a new approach for quantifying rotational symmetry based on vector analysis was described and compared with information obtained from a geometric morphometric analysis and a technique based on distance alone. A new method was developed that generates a polygon from the length and angle data of a structure and then quantifies the minimum change necessary to convert that polygon into a regular polygon. This technique yielded an asymmetry score (s) that can range from 0 (perfect symmetry) to 1 (complete asymmetry). Using digital images of Geranium robertianum flowers, this new method was compared with a technique based on lengths alone and with established geometric morphometric methods used to quantify shape variation. Asymmetry scores (s) more clearly described variation in symmetry and were more consistent with a visual assessment of the images than either comparative technique. This procedure is the first to quantify the asymmetry of radial structures accurately, uses easily obtainable measures to calculate the asymmetry score and allows comparisons among individuals and species, even when the comparisons involve structures with different patterns of symmetry. This technique enables the rigorous analysis of polysymmetric structures and provides a foundation for a better understanding of symmetry in nature.

  1. The arithmetic symmetry of monoatomic 2-nets.

    Science.gov (United States)

    Fadda, G; Zanzotto, G

    2000-01-01

    A recent paper [Pitteri & Zanzotto (1998). Acta Cryst. A54, 359-373] has proposed a framework for the study of the 'arithmetic symmetry' of multilattices (discrete triply periodic point sets in the affine space). The classical approach to multilattice symmetry considers the well known 'space groups', that is, the groups of affine isometries leaving a multilattice invariant. The ensuing classification counts 219 affine conjugacy (or isomorphism) classes of space groups in three dimensions, and 17 classes in two dimensions ('plane groups'). The arithmetic criterion gives a finer classification of multilattice symmetry than space (or plane) groups do. This paper is concerned with the systematic investigation of the arithmetic symmetry of multilattices in the simplest nontrivial case, that is, monoatomic 2-nets (planar lattices with two identical atoms in their unit cell). We show the latter to belong to five distinct arithmetic types. We also give the complete description of a fundamental domain for the action of the global symmetry group of 2-nets on the space of 2-net metrics.

  2. Dynamical symmetries of the shell model

    Energy Technology Data Exchange (ETDEWEB)

    Van Isacker, P

    2000-07-01

    The applications of spectrum generating algebras and of dynamical symmetries in the nuclear shell model are many and varied. They stretch back to Wigner's early work on the supermultiplet model and encompass important landmarks in our understanding of the structure of the atomic nucleus such as Racah's SU(2) pairing model and Elliot's SU(3) rotational model. One of the aims of this contribution has been to show the historical importance of the idea of dynamical symmetry in nuclear physics. Another has been to indicate that, in spite of being old, this idea continues to inspire developments that are at the forefront of today's research in nuclear physics. It has been argued in this contribution that the main driving features of nuclear structure can be represented algebraically but at the same time the limitations of the symmetry approach must be recognised. It should be clear that such approach can only account for gross properties and that any detailed description requires more involved numerical calculations of which we have seen many fine examples during this symposium. In this way symmetry techniques can be used as an appropriate starting point for detailed calculations. A noteworthy example of this approach is the pseudo-SU(3) model which starting from its initial symmetry Ansatz has grown into an adequate and powerful description of the nucleus in terms of a truncated shell model. (author)

  3. A new AVA attribute based on P-wave and S-wave reflectivities for overpressure prediction

    Science.gov (United States)

    Aleardi, Mattia; Mapelli, Luca; Mazzotti, Alfredo

    2017-05-01

    Pore pressure prediction is a key step for safe well drilling operations and is usually performed by deriving a velocity-pressure relationship calibrated to a reference well. However, in the last few decades, other seismic-based methods, such as the Amplitude versus Angle (AVA) technique, have been extended to predict anomalous pressure values. Concerning AVA analysis, in this work, we show that the expected pressure effect on the elastic rock properties is very different from the fluid effect, thus making the classical AVA attributes used for fluid prediction ineffective at highlighting pressure anomalies. Therefore, we propose a new AVA attribute to evidence the decrease in P-wave and S-wave reflectivity that usually occurs when passing from an overlying formation to an underlying overpressured one. This attribute can be easily derived from the intercept and gradient values extracted from the recorded seismic pre-stack data by means of the Shuey equation. To demonstrate the applicability of this new attribute for pore pressure prediction we show examples on synthetic seismic data and three applications to different field datasets over already drilled prospects. In the case of overpressured layers, this attribute shows anomalous responses, thus demonstrating its effectiveness in highlighting anomalous pore pressure regimes. In contrast, no anomalous attribute values are observed in cases characterized by a hydrostatic pore pressure regime.

  4. Shallow P- and S-wave velocities and site resonances in the St. Louis region, Missouri-Illinois

    Science.gov (United States)

    Williams, R.A.; Odum, J.K.; Stephenson, W.J.; Herrmann, Robert B.

    2007-01-01

    As part of the seismic hazard-mapping efforts in the St. Louis metropolitan area we determined the compressional and shear-wave velocities (Vp and Vs) to about a 40-m depth at 17 locations in this area. The Vs measurements were made using high-resolution seismic refraction and reflection methods. We find a clear difference in the Vs profiles between sites located on the river floodplains and those located in the upland urban areas of St. Louis. Vs30 (average Vs to 30-m depth) values in floodplain areas range from 200 to 290 m/s (NEHRP category D) and contrast with sites on the upland areas of St. Louis, which have Vs30 values ranging from 410 to 785 m/s (NEHRP categories C and B). The lower Vs30 values and earthquake recordings in the floodplains suggest a greater potential for stronger and more prolonged ground shaking in an earthquake. Spectral analysis of a M3.6 earthquake recorded on the St. Louis-area ANSS seismograph network indicates stronger shaking and potentially damaging S-wave resonant frequencies at NEHRP category D sites compared to ground motions at a rock site located on the Saint Louis University campus. ?? 2007, Earthquake Engineering Research Institute.

  5. Geometrical symmetries of nuclear systems: {{ D }}_{3h} and {{ T }}_{d} symmetries in light nuclei

    Science.gov (United States)

    Bijker, Roelof

    2016-07-01

    The role of discrete (or point-group) symmetries in α-cluster nuclei is discussed in the framework of the algebraic cluster model which describes the relative motion of the α-particles. Particular attention is paid to the discrete symmetry of the geometric arrangement of the α-particles, and the consequences for the structure of the corresponding rotational bands. The method is applied to study cluster states in the nuclei 12C and 16O. The observed level sequences can be understood in a simple way as a consequence of the underlying discrete symmetry that characterizes the geometrical configuration of the α-particles, i.e. an equilateral triangle with {{ D }}3h symmetry for 12C, and a tetrahedron with {{ T }}d symmetry for 16O. The structure of rotational bands provides a fingerprint of the underlying geometrical configuration of α-particles.

  6. Band gaps and cavity modes in dual phononic and photonic strip waveguides

    Directory of Open Access Journals (Sweden)

    Y. Pennec

    2011-12-01

    Full Text Available We discuss theoretically the simultaneous existence of phoxonic, i.e., dual phononic and photonic, band gaps in a periodic silicon strip waveguide. The unit-cell of this one-dimensional waveguide contains a hole in the middle and two symmetric stubs on the sides. Indeed, stubs and holes are respectively favorable for creating a phononic and a photonic band gap. Appropriate geometrical parameters allow us to obtain a complete phononic gap together with a photonic gap of a given polarization and symmetry. The insertion of a cavity inside the perfect structure provides simultaneous confinement of acoustic and optical waves suitable to enhance the phonon-photon interaction.

  7. Operational symmetries basic operations in physics

    CERN Document Server

    Saller, Heinrich

    2017-01-01

    This book describes the endeavour to relate the particle spectrum with representations of operational electroweak spacetime, in analogy to the atomic spectrum as characterizing representations of hyperbolic space. The spectrum of hyperbolic position space explains the properties of the nonrelativistic atoms; the spectrum of electroweak spacetime is hoped to explain those of the basic interactions and elementary particles. In this book, the theory of operational symmetries is developed from the numbers, from Plato’s and Kepler’s symmetries over the simple Lie groups to their applications in nonrelativistic, special relativistic and general relativistic quantum theories with the atomic spectrum for hyperbolic position and, in first attempts, the particle spectrum for electroweak spacetime. The standard model of elementary particles and interactions is characterized by a symmetry group. In general, as initiated by Weyl and stressed by Heisenberg, quantum theory can be built as a theory of operation groups an...

  8. Symmetry transforms for ideal magnetohydrodynamics equilibria.

    Science.gov (United States)

    Bogoyavlenskij, Oleg I

    2002-11-01

    A method for constructing ideal magnetohydrodynamics (MHD) equilibria is introduced. The method consists of the application of symmetry transforms to any known MHD equilibrium [ O. I. Bogoyavlenskij, Phys. Rev. E. 62, 8616, (2000)]. The transforms break the geometrical symmetries of the field-aligned solutions and produce continuous families of the nonsymmetric MHD equilibria. The method of symmetry transforms also allows to obtain MHD equilibria with current sheets and exact solutions with noncollinear vector fields B and V. A model of the nonsymmetric astrophysical jets outside of their accretion disks is developed. The total magnetic and kinetic energy of the jet is finite in any layer c(1)ball lightning with dynamics of plasma inside the fireball.

  9. Supersymmetric defect models and mirror symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Hook, Anson; Kachru, Shamit; Torroba, Gonzalo

    2013-11-01

    We study supersymmetric field theories in three space-time dimensions doped by various configurations of electric charges or magnetic fluxes. These are supersymmetric avatars of impurity models. In the presence of additional sources such configurations are shown to preserve half of the supersymmetries. Mirror symmetry relates the two sets of configurations. We discuss the implications for impurity models in 3d NN = 4 QED with a single charged hypermultiplet (and its mirror, the theory of a free hypermultiplet) as well as 3d NN = 2 QED with one flavor and its dual, a supersymmetric Wilson-Fisher fixed point. Mirror symmetry allows us to find backreacted solutions for arbitrary arrays of defects in the IR limit of NN = 4 QED. Our analysis, complemented with appropriate string theory brane constructions, sheds light on various aspects of mirror symmetry, the map between particles and vortices and the emergence of ground state entropy in QED at finite density.

  10. New Algorithms For Automated Symmetry Recognition

    Science.gov (United States)

    Paul, Jody; Kilgore, Tammy Elaine; Klinger, Allen

    1988-02-01

    In this paper we present new methods for computer-based symmetry identification that combine elements of group theory and pattern recognition. Detection of symmetry has diverse applications including: the reduction of image data to a manageable subset with minimal information loss, the interpretation of sensor data,1 such as the x-ray diffraction patterns which sparked the recent discovery of a new "quasicrystal" phase of solid matter,2 and music analysis and composition.3,4,5 Our algorithms are expressed as parallel operations on the data using the matrix representation and manipulation features of the APL programming language. We demonstrate the operation of programs that characterize symmetric and nearly-symmetric patterns by determining the degree of invariance with respect to candidate symmetry transformations. The results are completely general; they may be applied to pattern data of arbitrary dimension and from any source.

  11. Homological mirror symmetry and tropical geometry

    CERN Document Server

    Catanese, Fabrizio; Kontsevich, Maxim; Pantev, Tony; Soibelman, Yan; Zharkov, Ilia

    2014-01-01

    The relationship between Tropical Geometry and Mirror Symmetry goes back to the work of Kontsevich and Y. Soibelman (2000), who applied methods of non-archimedean geometry (in particular, tropical curves) to Homological Mirror Symmetry. In combination with the subsequent work of Mikhalkin on the “tropical” approach to Gromov-Witten theory, and the work of Gross and Siebert, Tropical Geometry has now become a powerful tool. Homological Mirror Symmetry is the area of mathematics concentrated around several categorical equivalences connecting symplectic and holomorphic (or algebraic) geometry. The central ideas first appeared in the work of Maxim Kontsevich (1993). Roughly speaking, the subject can be approached in two ways: either one uses Lagrangian torus fibrations of Calabi-Yau manifolds (the so-called Strominger-Yau-Zaslow picture, further developed by Kontsevich and Soibelman) or one uses Lefschetz fibrations of symplectic manifolds (suggested by Kontsevich and further developed by Seidel). Tropical Ge...

  12. Quantum mechanics and hidden superconformal symmetry

    Science.gov (United States)

    Bonezzi, R.; Corradini, O.; Latini, E.; Waldron, A.

    2017-12-01

    Solvability of the ubiquitous quantum harmonic oscillator relies on a spectrum generating osp (1 |2 ) superconformal symmetry. We study the problem of constructing all quantum mechanical models with a hidden osp (1 |2 ) symmetry on a given space of states. This problem stems from interacting higher spin models coupled to gravity. In one dimension, we show that the solution to this problem is the Vasiliev-Plyushchay family of quantum mechanical models with hidden superconformal symmetry obtained by viewing the harmonic oscillator as a one dimensional Dirac system, so that Grassmann parity equals wave function parity. These models—both oscillator and particlelike—realize all possible unitary irreducible representations of osp (1 |2 ).

  13. Symmetry issues in Directly Irradiated Targets

    Directory of Open Access Journals (Sweden)

    Ramis R.

    2013-11-01

    Full Text Available In direct drive Inertial Confinement Fusion (ICF, the typical laser beam to laser beam angle is around 30°. This fact makes the study of the irradiation symmetry a genuine 3D problem. In this paper we use the three dimensional version of the MULTI hydrocode to assess the symmetry of such ICF implosions. More specifically, we study a shock-ignition proposal for the Laser-Mégajoule facility (LMJ in which two of the equatorial beam cones are used to implode and precompress a spherical capsule (the “reference” capsule of HiPER project made of 0.59 mg of pure Deuterium-Tritium mixture. The symmetry of this scheme is analysed and optimized to get a design inside the operating limits of LMJ. The studied configuration has been found essentially axial-symmetric, so that the use of 2D hydrocodes would be appropriate for this specific situation.

  14. 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.

  15. STS, symmetry and post-truth.

    Science.gov (United States)

    Lynch, Michael

    2017-08-01

    This essay takes up a series of questions about the connection between 'symmetry' in Science and Technology Studies (STS) and 'post-truth' in contemporary politics. A recent editorial in this journal by Sergio Sismondo argues that current discussions of 'post-truth' have little to do with conceptions of 'symmetry' or with concerns about 'epistemic democracy' in STS, while others, such as Steve Fuller and Harry Collins, insist that there are such connections. The present essay discusses a series of questions about the meaning of 'post-truth' and 'symmetry', and the connections of those concepts to each other and to 'epistemic democracy'. The essay ends with a series of other questions about STS and contemporary politics, and an invitation to further discussions.

  16. 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.

  17. Increased sensitivity to mirror symmetry in autism.

    Directory of Open Access Journals (Sweden)

    Audrey Perreault

    2011-04-01

    Full Text Available Can autistic people see the forest for the trees? Ongoing uncertainty about the integrity and role of global processing in autism gives special importance to the question of how autistic individuals group local stimulus attributes into meaningful spatial patterns. We investigated visual grouping in autism by measuring sensitivity to mirror symmetry, a highly-salient perceptual image attribute preceding object recognition. Autistic and non-autistic individuals were asked to detect mirror symmetry oriented along vertical, oblique, and horizontal axes. Both groups performed best when the axis was vertical, but across all randomly-presented axis orientations, autistics were significantly more sensitive to symmetry than non-autistics. We suggest that under some circumstances, autistic individuals can take advantage of parallel access to local and global information. In other words, autistics may sometimes see the forest and the trees, and may therefore extract from noisy environments genuine regularities which elude non-autistic observers.

  18. Conservation Laws, Symmetries, and Elementary Particles

    Science.gov (United States)

    Hoekzema, Dick; Schooten, Gert; van den Berg, Ed; Lijnse, Piet

    2005-05-01

    The following student text on conservation laws, symmetries, and elementary particles was developed in a Dutch project for teaching modern physics to the top stream of the sixth year of secondary education (age 17-18). In a series of 35 lessons of 45-50 minutes each, students study particle-wave duality, the Heisenberg principle, probability models for properties of particles, the particle in a box, and applications, elementary particles, and astrophysics (http://www.phys.uu.nl/˜wwwpmn). In this paper we focus on particle physics and the key concepts of this chapter are: transformation, reaction equation, conservation laws, and symmetry. For recent literature regarding the teaching of symmetries and/or elementary particles, we refer to articles by Hill & Lederman, Pascolini & Pietroni,2 Kalmus,3 O'Connell,4 and Hanley.5

  19. Confinement/deconfinement transition from symmetry breaking in gauge/gravity duality

    Energy Technology Data Exchange (ETDEWEB)

    Čubrović, Mihailo [Institute for Theoretical Physics, University of Cologne,Zülpicher Strasse 77, D-50937, Cologne (Germany)

    2016-10-19

    We study the confinement/deconfinement transition in a strongly coupled system triggered by an independent symmetry-breaking quantum phase transition in gauge/gravity duality. The gravity dual is an Einstein-scalar-dilaton system with AdS near-boundary behavior and soft wall interior at zero scalar condensate. We study the cases of neutral and charged condensate separately. In the former case the condensation breaks the discrete ℤ{sub 2} symmetry while a charged condensate breaks the continuous U(1) symmetry. After the condensation of the order parameter, the non-zero vacuum expectation value of the scalar couples to the dilaton, changing the soft wall geometry into a non-confining and anisotropically scale-invariant infrared metric. In other words, the formation of long-range order is immediately followed by the deconfinement transition and the two critical points coincide. The confined phase has a scale — the confinement scale (energy gap) which vanishes in the deconfined case. Therefore, the breaking of the symmetry of the scalar (ℤ{sub 2} or U(1)) in turn restores the scaling symmetry in the system and neither phase has a higher overall symmetry than the other. When the scalar is charged the phase transition is continuous which goes against the Ginzburg-Landau theory where such transitions generically only occur discontinuously. This phenomenon has some commonalities with the scenario of deconfined criticality. The mechanism we have found has applications mainly in effective field theories such as quantum magnetic systems. We briefly discuss these applications and the relation to real-world systems.

  20. Microtremor exploration for shallow S-wave velocity profiles at stations in local strong motion network in Bursa, Yalova, and Kocaeli in north-western Turkey

    Science.gov (United States)

    Özmen, Özgür Tuna; Yamanaka, Hiroaki; Chimoto, Kosuke; Çeken, Ulubey; Alkan, Mehmet Akif; Tekin, Kudret; Ateş, Erkan

    2017-05-01

    We conducted microtremor array surveys for shallow S-wave velocity profiles at 20 sites in Bursa, Yalova and Kocaeli provinces in the north-western part of Turkey to provide fundamental data to assess the seismic hazard in the area. All of the measurement sites were positioned very close to strong motion stations belonging to the Disaster and Emergency Management Presidency of Turkey (AFAD) in order to further understand site amplification factors in strong motion records. Of the 20 study sites, two were located in Yalova, four in Bursa and 14 in Kocaeli. We temporarily installed two small arrays to obtain simultaneous records of vertical microtremors. Then, the spatial autocorrelation method was applied to retrieve Rayleigh wave phase velocity curves in a frequency range from 1 to 30 Hz from the array records. The phase velocities in the western part of the Kocaeli area are low across a wide frequency range, while relatively high phase velocities are found in the eastern part of the Kocaeli province. The phase velocities in the Yalova and Bursa provinces are widely distributed suggesting large variations in soil conditions. The observed phase velocity curve at each site was inverted to a one-dimensional (1D) S-wave velocity profile to a depth of 100 m, using a hybrid heuristic inversion method. All the S-wave velocity profiles in the eastern Kocaeli area are similar; however, the sites in the western Kocaeli and Yalova-Bursa areas have profiles with different features from the others. Finally, we discuss amplification factors for S-waves using the inverted profiles. The dominant fundamental periods of the amplification factors were distributed in a frequency range from 0.7 to 5 Hz. The profiles obtained are also used to map average S-wave velocities in the study area, with an addition of existing data at strong motion stations of the AFAD.

  1. Chiral symmetry in light-front QCD

    Science.gov (United States)

    Wu, Menh-Hsiu; Zhang, Wei-Min

    2004-04-01

    The definition of chiral transformations in light-front field theory is very different from the conventional form in equal-time formalism. We study the consistency of chiral transformations and chiral symmetry in light-front QCD and derive a complete new light-front axial-vector current for QCD. The breaking of chiral symmetry in light-front QCD is only associated with helicity flip interaction between quarks and gluons. Remarkably, the new axial-vector current does not contain the pion pole part so that the associate chiral charge smoothly describes pion transitions for various hadronic processes.

  2. Chiral Symmetry in Light-front QCD

    OpenAIRE

    Wu, Meng-Hsiu; Zhang, Wei-Min

    2003-01-01

    The definition of chiral transformations in light-front field theory is very different from the conventional form in equal-time formalism. We study the consistency of chiral transformations and chiral symmetry in light-front QCD and derive a complete new light-front axial-vector current for QCD. The breaking of chiral symmetry in light-front QCD is only associated with helicity flip interaction between quarks and gluons. Remarkably, the new axial-vector current does not contain the pion pole ...

  3. Toward Measuring Network Aesthetics Based on Symmetry

    Directory of Open Access Journals (Sweden)

    Zengqiang Chen

    2017-05-01

    Full Text Available In this exploratory paper, we discuss quantitative graph-theoretical measures of network aesthetics. Related work in this area has typically focused on geometrical features (e.g., line crossings or edge bendiness of drawings or visual representations of graphs which purportedly affect an observer’s perception. Here we take a very different approach, abandoning reliance on geometrical properties, and apply information-theoretic measures to abstract graphs and networks directly (rather than to their visual representaions as a means of capturing classical appreciation of structural symmetry. Examples are used solely to motivate the approach to measurement, and to elucidate our symmetry-based mathematical theory of network aesthetics.

  4. Black Hole Thermodynamics and Lorentz Symmetry

    Science.gov (United States)

    Jacobson, Ted; Wall, Aron C.

    2010-08-01

    Recent developments point to a breakdown in the generalized second law of thermodynamics for theories with Lorentz symmetry violation. It appears possible to construct a perpetual motion machine of the second kind in such theories, using a black hole to catalyze the conversion of heat to work. Here we describe and extend the arguments leading to that conclusion. We suggest the inference that local Lorentz symmetry may be an emergent property of the macroscopic world with origins in a microscopic second law of causal horizon thermodynamics.

  5. Partial restoration of chiral symmetry inside hadrons

    Energy Technology Data Exchange (ETDEWEB)

    Iritani, Takumi [Yukawa Institute for Theoretical Physics (YITP) (Japan); Cossu, Guido [High Energy Accelerator Research Organization (KEK) (Japan); Hashimoto, Shoji [High Energy Accelerator Research Organization (KEK) (Japan); School of High Energy Accelerator Science, The Graduate University for Advanced Studies (Sokendai) (Japan)

    2016-01-22

    We investigate the spatial distribution of the chiral condensate around static color sources for both quark-antiquark and three-quark systems. In the QCD vacuum a tube-like structure of chromo fields appears between color sources, which leads to a linearly confining potential. We show that the magnitude of the condensate is reduced inside the flux-tube, which suggests that chiral symmetry is partially restored inside the hadrons. By using a static baryon source in a periodic box as a model of the nuclear matter, we estimate the restoration of chiral symmetry with finite baryon number density.

  6. Partial restoration of chiral symmetry inside hadrons

    Science.gov (United States)

    Iritani, Takumi; Cossu, Guido; Hashimoto, Shoji

    2016-01-01

    We investigate the spatial distribution of the chiral condensate around static color sources for both quark-antiquark and three-quark systems. In the QCD vacuum a tube-like structure of chromo fields appears between color sources, which leads to a linearly confining potential. We show that the magnitude of the condensate is reduced inside the flux-tube, which suggests that chiral symmetry is partially restored inside the hadrons. By using a static baryon source in a periodic box as a model of the nuclear matter, we estimate the restoration of chiral symmetry with finite baryon number density.

  7. Gauge symmetries and structure of proteins

    Directory of Open Access Journals (Sweden)

    Molochkov Alexander

    2017-01-01

    Full Text Available We discuss the gauge field theory approach to protein structure study, which allows a natural way to introduce collective degrees of freedom and nonlinear topological structures. Local symmetry of proteins and its breaking in the medium is considered, what allows to derive Abelian Higgs model of protein backbone, correct folding of which is defined by gauge symmetry breaking due hydrophobic forces. Within this model structure of protein backbone is defined by superposition of one-dimensional topological solitons (kinks, what allows to reproduce the three-dimensional structure of the protein backbone with precision up to 1A and to predict its dynamics.

  8. Singularities, horizons, firewalls, and local conformal symmetry

    CERN Document Server

    Hooft, Gerard 't

    2015-01-01

    The Einstein-Hilbert theory of gravity can be rephrased by focusing on local conformal symmetry as an exact, but spontaneously broken symmetry of nature. The conformal component of the metric field is then treated as a dilaton field with only renormalizable interactions. This imposes constraints on the theory, which can also be viewed as demanding regularity of the action as the dilaton field variable tends to 0. In other words, we have constraints on the small distance behaviour. Our procedure appears to turn a black hole into a regular, topologically trivial soliton without singularities, horizons of firewalls, but many questions remain.

  9. Symmetry characterization of electrons and lattice excitations

    Directory of Open Access Journals (Sweden)

    Schober H.

    2012-03-01

    Full Text Available Symmetry concerns all aspects of a physical system from the electronic orbitals to structural and magnetic excitations. In this article we will try to elaborate the fundamental connection between symmetry and excitations. As excitations are manyfold in physical systems it is impossible to treat them exhaustively. We thus concentrate on the two topics of Bloch electrons and phonons. These two examples are complementary in the sense that Bloch electrons describe single particles in an external periodic potential while phonons exemplify a decoupled system of interacting particles. The way we develop the argument gives as by-product a short account of molecular orbitals and molecular vibrations.

  10. Symmetry in bonding and spectra an introduction

    CERN Document Server

    Douglas, Bodie E

    1985-01-01

    Many courses dealing with the material in this text are called ""Applications of Group Theory."" Emphasizing the central role and primary importance of symmetry in the applications, Symmetry in Bonding and Spectra enables students to handle applications, particularly applications to chemical bonding and spectroscopy. It contains the essential background in vectors and matrices for the applications, along with concise reviews of simple molecular orbital theory, ligand field theory, and treatments of molecular shapes, as well as some quantum mechanics. Solved examples in the text illustra

  11. Masses, mixings, Yukawa couplings and their symmetries

    CERN Document Server

    Santamaría, A

    1993-01-01

    We present a method to find the number of real and imaginary observable parameters coming from the Yukawa sector in an arbitrary gauge theory. The method leads naturally to a classification of Yukawa couplings according to their symmetries and suggests a new parametrization of masses and mixings that is useful to study the behaviour of Yukawa couplings under the renormalization group. We apply it to some examples based on the Standard Model with Yukawa couplings obeying various chiral symmetries. We also show how our method of parameter counting can be used in some models with an enlarged leptonic sector.

  12. High-symmetry organic scintillator systems

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Patrick L.

    2017-09-05

    An ionizing radiation detector or scintillator system includes a scintillating material comprising an organic crystalline compound selected to generate photons in response to the passage of ionizing radiation. The organic compound has a crystalline symmetry of higher order than monoclinic, for example an orthorhombic, trigonal, tetragonal, hexagonal, or cubic symmetry. A photodetector is optically coupled to the scintillating material, and configured to generate electronic signals having pulse shapes based on the photons generated in the scintillating material. A discriminator is coupled to the photon detector, and configured to discriminate between neutrons and gamma rays in the ionizing radiation based on the pulse shapes of the output signals.

  13. Spontaneous symmetry breaking in gauge theories.

    Science.gov (United States)

    Kibble, T W B

    2015-01-13

    The aim of this historical article is to describe the development of the idea of spontaneous symmetry breaking in gauge theories as seen from my perspective as a member of Abdus Salam's group at Imperial College London, UK. Beginning with an account of particle physics in the years after the Second World War, I describe early attempts at constructing a unified theory of weak and electromagnetic interactions, the obstacles encountered and how they were eventually overcome with the mass-generating mechanism incorporating the idea of spontaneous symmetry breaking, one of whose features is the now-famous Higgs boson.

  14. High-symmetry organic scintillator systems

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Patrick L.

    2018-02-06

    An ionizing radiation detector or scintillator system includes a scintillating material comprising an organic crystalline compound selected to generate photons in response to the passage of ionizing radiation. The organic compound has a crystalline symmetry of higher order than monoclinic, for example an orthorhombic, trigonal, tetragonal, hexagonal, or cubic symmetry. A photodetector is optically coupled to the scintillating material, and configured to generate electronic signals having pulse shapes based on the photons generated in the scintillating material. A discriminator is coupled to the photon detector, and configured to discriminate between neutrons and gamma rays in the ionizing radiation based on the pulse shapes of the output signals.

  15. The role of symmetry in the interpretation of physical theories

    Science.gov (United States)

    Caulton, Adam

    2015-11-01

    The symmetries of a physical theory are often associated with two things: conservation laws (via e.g. Noether's and Schur's theorems) and representational redundancies ("gauge symmetry"). But how can a physical theory's symmetries give rise to interesting (in the sense of non-trivial) conservation laws, if symmetries are transformations that correspond to no genuine physical difference? In this paper, I argue for a disambiguation in the notion of symmetry. The central distinction is between what I call "analytic" and "synthetic" symmetries, so called because of an analogy with analytic and synthetic propositions. "Analytic" symmetries are the turning of idle wheels in a theory's formalism, and correspond to no physical change; "synthetic" symmetries cover all the rest. I argue that analytic symmetries are distinguished because they act as fixed points or constraints in any interpretation of a theory, and as such are akin to Poincaré's conventions or Reichenbach's 'axioms of co-ordination', or 'relativized constitutive a priori principles'.

  16. Continuous Global Symmetries and Hyperweak Interactions in String Compactifications

    CERN Document Server

    Burgess, C P; Hung, L-Y; Kom, C H; Maharana, A; Quevedo, Fernando

    2008-01-01

    We revisit general arguments for the absence of exact continuous global symmetries in string compactifications and extend them to D-brane models. We elucidate the various ways approximate continuous global symmetries arise in the 4-dimensional effective action. In addition to two familiar methods - axionic Peccei-Quinn symmetries and remnant global abelian symmetries from Green-Schwarz gauge symmetry breaking - we identify new ways to generate approximate continuous global symmetries. Two methods stand out, both of which occur for local brane constructions within the LARGE volume scenario of moduli stabilisation. The first is the generic existence of continuous non-abelian global symmetries associated with local Calabi-Yau isometries. These symmetries are exact in the non-compact limit and are spontaneously broken by the LARGE volume, with breaking effects having phenomenologically interesting sizes \\sim 0.01 for plausible choices for underlying parameters. Such approximate flavour symmetries are phenomenolog...

  17. Two-gap superconductivity in Mo8Ga41 and its evolution upon vanadium substitution

    Science.gov (United States)

    Verchenko, V. Yu.; Khasanov, R.; Guguchia, Z.; Tsirlin, A. A.; Shevelkov, A. V.

    2017-10-01

    Zero-field and transverse-field muon spin rotation/relaxation (μ SR ) experiments were undertaken in order to elucidate the microscopic properties of a strongly coupled superconductor Mo8Ga41 with Tc=9.8 K. The upper critical field extracted from the transverse-field μ SR data exhibits significant reduction with respect to the data from thermodynamic measurements indicating the coexistence of two independent length scales in the superconducting state. Accordingly, the temperature-dependent magnetic penetration depth of Mo8Ga41 is described using a model in which two s wave superconducting gaps are assumed. A V for Mo substitution in the parent compound leads to the complete suppression of one superconducting gap, and Mo7VGa41 is well described within the single s wave gap scenario. The reduction in the superfluid density and the evolution of the low-temperature resistivity upon V substitution indicate the emergence of a competing state in Mo7VGa41 that may be responsible for the closure of one of the superconducting gaps.

  18. Crust-mantle coupling mechanism in Cameroon, West Africa, revealed by 3D S-wave velocity and azimuthal anisotropy

    Science.gov (United States)

    Ojo, Adebayo Oluwaseun; Ni, Sidao; Chen, Haopeng; Xie, Jun

    2018-01-01

    To understand the depth variation of deformation beneath Cameroon, West Africa, we developed a new 3D model of S-wave isotropic velocity and azimuthal anisotropy from joint analysis of ambient seismic noise and earthquake surface wave dispersion. We found that the Cameroon Volcanic Line (CVL) is well delineated by slow phase velocities in contrast with the neighboring Congo Craton, in agreement with previous studies. Apart from the Congo Craton and the Oubanguides Belt, the uppermost mantle revealed a relatively slow velocity indicating a thinned or thermally altered lithosphere. The direction of fast axis in the upper crust is mostly NE-SW, but trending approximately N-S around Mt. Oku and the southern CVL. The observed crustal azimuthal anisotropy is attributed to alignment of cracks and crustal deformation related to magmatic activities. A widespread zone of weak-to-zero azimuthal anisotropy in the mid-lower crust shows evidence for vertical mantle flow or isotropic mid-lower crust. In the uppermost mantle, the fast axis direction changed from NE-SW to NW-SE around Mt. Oku and northern Cameroon. This suggests a layered mechanism of deformation and revealed that the mantle lithosphere has been deformed. NE-SW fast azimuths are observed beneath the Congo Craton and are consistent with the absolute motion of the African plate, suggesting a mantle origin for the observed azimuthal anisotropy. Our tomographically derived fast directions are consistent with the local SKS splitting results in some locations and depths, enabling us to constrain the origin of the observed splitting. The different feature of azimuthal anisotropy in the upper crust and the uppermost mantle implies decoupling between deformation of crust and mantle in Cameroon.

  19. Insights in P- and S-wave relative traveltime tomography from analysing finite-frequency Fréchet kernels

    Science.gov (United States)

    Maupin, Valérie; Kolstrup, Marianne Lanzky

    2015-09-01

    Regional body-wave tomography, also called ACH tomography, is the inversion of relative traveltime residuals of teleseismic body waves measured at regional networks. We analyse the characteristics of the finite-frequency Fréchet kernels for P and S waves for this kind of tomography. Using a simplified geometry enables us to use the complete Green's function in the expression of the Fréchet kernels and analyse elements, which are usually neglected, like the importance of the near-field terms and the P-wave traveltime sensitivity to shear wave velocity variations. By comparing the kernels of the relative residuals and absolute ones, we show that relative residuals have a reduced sensitivity to heterogeneities of large dimensions, and that this reduction is a generalization of the fact that the average model is not recovered in ACH tomography. This sensitivity reduction affects equally short- and long-period residuals. We show in addition the presence of a sensitivity reduction at large depth for the long-period waves. Kernels and reflectivity impulse responses of the crust are used to analyse if crustal corrections should be made frequency-dependent in finite-frequency regional tomography. We find that in most cases the frequency dependence due to reverberations is substantial, and that in many realistic network configurations ray theory is unlikely to be well appropriate to compute crustal corrections for the long-period waves. We also find that the lateral dimensions of the crust affecting the traveltimes is frequency dependent and reaches, at long periods, 50 km for sedimentary basins and 100 km for Moho depth.

  20. Topological Symmetry, Spin Liquids and CFT Duals of Polyakov Model with Massless Fermions

    Energy Technology Data Exchange (ETDEWEB)

    Unsal, Mithat

    2008-04-30

    We prove the absence of a mass gap and confinement in the Polyakov model with massless complex fermions in any representation of the gauge group. A U(1){sub *} topological shift symmetry protects the masslessness of one dual photon. This symmetry emerges in the IR as a consequence of the Callias index theorem and abelian duality. For matter in the fundamental representation, the infrared limits of this class of theories interpolate between weakly and strongly coupled conformal field theory (CFT) depending on the number of flavors, and provide an infinite class of CFTs in d = 3 dimensions. The long distance physics of the model is same as certain stable spin liquids. Altering the topology of the adjoint Higgs field by turning it into a compact scalar does not change the long distance dynamics in perturbation theory, however, non-perturbative effects lead to a mass gap for the gauge fluctuations. This provides conceptual clarity to many subtle issues about compact QED{sub 3} discussed in the context of quantum magnets, spin liquids and phase fluctuation models in cuprate superconductors. These constructions also provide new insights into zero temperature gauge theory dynamics on R{sup 2,1} and R{sup 2,1} x S{sup 1}. The confined versus deconfined long distance dynamics is characterized by a discrete versus continuous topological symmetry.

  1. Symmetry-protected topological phases of one-dimensional interacting fermions with spin-charge separation

    Science.gov (United States)

    Montorsi, Arianna; Dolcini, Fabrizio; Iotti, Rita C.; Rossi, Fausto

    2017-06-01

    The low energy behavior of a huge variety of one-dimensional interacting spinful fermionic systems exhibits spin-charge separation, described in the continuum limit by two sine-Gordon models decoupled in the charge and spin channels. Interaction is known to induce, besides the gapless Luttinger liquid phase, eight possible gapped phases, among which are the Mott, Haldane, charge-/spin-density, and bond-ordered wave insulators, and the Luther Emery liquid. Here we prove that some of these physically distinct phases have nontrivial topological properties, notably the presence of degenerate protected edge modes with fractionalized charge/spin. Moreover, we show that the eight gapped phases are in one-to-one correspondence with the symmetry-protected topological (SPT) phases classified by group cohomology theory in the presence of particle-hole symmetry P. The latter result is also exploited to characterize SPT phases by measurable nonlocal order parameters which follow the system evolution to the quantum phase transition. The implications on the appearance of exotic orders in the class of microscopic Hubbard Hamiltonians, possibly without P symmetry at higher energies, are discussed.

  2. Bilayer Graphene as a Platform for Bosonic Symmetry-Protected Topological States.

    Science.gov (United States)

    Bi, Zhen; Zhang, Ruixing; You, Yi-Zhuang; Young, Andrea; Balents, Leon; Liu, Chao-Xing; Xu, Cenke

    2017-03-24

    Bosonic symmetry protected topological (BSPT) states, the bosonic analogue of topological insulators, have attracted enormous theoretical interest in the last few years. Although BSPT states have been classified by various approaches, there is so far no successful experimental realization of any BSPT state in two or higher dimensions. In this paper, we propose that a two-dimensional BSPT state with U(1)×U(1) symmetry can be realized in bilayer graphene in a magnetic field. Here the two U(1) symmetries represent total spin S^{z} and total charge conservation, respectively. The Coulomb interaction plays a central role in this proposal-it gaps out all the fermions at the boundary, so that only bosonic charge and spin degrees of freedom are gapless and protected at the edge. Based on the above conclusion, we propose that the bulk quantum phase transition between the BSPT and trivial phase, which can be driven by applying both magnetic and electric fields, can become a "bosonic phase transition" with interactions. That is, only bosonic modes close their gap at the transition, which is fundamentally different from all the well-known topological insulator to trivial insulator transitions that occur for free fermion systems. We discuss various experimental consequences of this proposal.

  3. Ligament tension in the ACL-deficient knee: assessment of medial and lateral gaps.

    Science.gov (United States)

    Mayman, David; Plaskos, Christopher; Kendoff, Daniel; Wernecke, G; Pearle, Andrew D; Laskin, Richard

    2009-06-01

    Obtaining symmetric and balanced gaps under equilateral loads is a common goal in posterior cruciate ligament (PCL)-retaining and -sacrificing TKAs. Owing to limitations in existing surgical tensors, however, tensing knee ligaments with standardized and symmetric loads has been possible only with the patella subluxated or everted. We therefore determined the influences of (1) patellar eversion versus complete reduction, (2) PCL resection, and (3) load magnitude on gap symmetry and balance in the anterior cruciate ligament (ACL)-deficient knee. We used a novel computer-controlled tensioner to measure gaps in 10 cadavers with an applied force of 50 N, 75 N, and 100 N per side. Gap data were acquired at 0 masculine, 30 masculine, 60 masculine, 90 masculine, and 120 masculine flexion with the patella reduced and everted and with the PCL intact and resected. Everting the patella tightened the medial and lateral flexion gaps between 90 masculine and 120 masculine by 0.7 mm to 2.7 mm. PCL resection increased gaps from 30 degrees to 120 degrees by 1 mm to 3 mm. Increasing the force from 50 N to 100 N increased the mean gap by 0.5 mm. Everting the patella and resecting the PCL influenced gap balance and symmetry. Surgeons should be aware of how these conditions affect gaps during assessment and balancing.

  4. Wide-Gap Chalcopyrites

    CERN Document Server

    Siebentritt, Susanne

    2006-01-01

    Chalcopyrites, in particular those with a wide band gap, are fascinating materials in terms of their technological potential in the next generation of thin-film solar cells and in terms of their basic material properties. They exhibit uniquely low defect formation energies, leading to unusual doping and phase behavior and to extremely benign grain boundaries. This book collects articles on a number of those basic material properties of wide-gap chalcopyrites, comparing them to their low-gap cousins. They explore the doping of the materials, the electronic structure and the transport through interfaces and grain boundaries, the formation of the electric field in a solar cell, the mechanisms and suppression of recombination, the role of inhomogeneities, and the technological role of wide-gap chalcopyrites.

  5. Topological quantum phase transition from mirror to time reversal symmetry protected topological insulator.

    Science.gov (United States)

    Mandal, Partha S; Springholz, Gunther; Volobuev, Valentine V; Caha, Ondrej; Varykhalov, Andrei; Golias, Evangelos; Bauer, Günther; Rader, Oliver; Sánchez-Barriga, Jaime

    2017-10-17

    Topological insulators constitute a new phase of matter protected by symmetries. Time-reversal symmetry protects strong topological insulators of the Z2 class, which possess an odd number of metallic surface states with dispersion of a Dirac cone. Topological crystalline insulators are merely protected by individual crystal symmetries and exist for an even number of Dirac cones. Here, we demonstrate that Bi-doping of Pb1-x Sn x Se (111) epilayers induces a quantum phase transition from a topological crystalline insulator to a Z2 topological insulator. This occurs because Bi-doping lifts the fourfold valley degeneracy and induces a gap at [Formula: see text], while the three Dirac cones at the [Formula: see text] points of the surface Brillouin zone remain intact. We interpret this new phase transition as caused by a lattice distortion. Our findings extend the topological phase diagram enormously and make strong topological insulators switchable by distortions or electric fields.Transitions between topological phases of matter protected by different symmetries remain rare. Here, Mandal et al. report a quantum phase transition from a topological crystalline insulator to a Z2 topological insulator by doping Bi into Pb1-x Sn x Se (111) thin films.

  6. Spin and pseudospin symmetries in the single-Λ spectrum

    Science.gov (United States)

    Sun, Ting-Ting; Lu, Wan-Li; Zhang, Shi-Sheng

    2017-10-01

    We explore spin and pseudospin symmetries in the single-Λ spectrum within the framework of relativistic mean-field theory. We find that the spin symmetry of the single-Λ spectrum maintains, which is consistent with experimental results of small spin-orbit splitting, whereas the approximate pseudospin symmetry is quite similar to that of nucleons. More interestingly, the ω Λ Λ tensor coupling has opposite effects on these symmetries which makes the spin symmetry better but the pseudospin symmetry worse. This can be understood by the negative value of the ω Λ Λ tensor potential, which reduces the spin-orbit potential while increasing the pseudospin-orbit potential.

  7. The Gender Pay Gap

    OpenAIRE

    Alan Manning

    2006-01-01

    Empirical research on gender pay gaps has traditionally focused on the role of gender-specific factors, particularly gender differences in qualifications and differences in the treatment of otherwise equally qualified male and female workers (i.e., labor market discrimination). This paper explores the determinants of the gender pay gap and argues for the importance of an additional factor, wage structure, the array of prices set for labor market skills and the rewards received for employment ...

  8. Introduction "Workplace (a)symmetries: multimodal perspectives"

    DEFF Research Database (Denmark)

    Asmuss, Birte

    and gaze) serves as a resource to accomplish specific interactional goals (Schegloff, 1998; Goodwin, 2003; Stivers 2008). By linking to the growing body of research on multimodal aspects of interaction (Llewellyn 2011, Stivers and Sidnell, 2005; Mondada, 2007), the panel will thus contribute to our...... understanding of workplace symmetries and asymmetries as multimodal accomplishments....

  9. 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.

  10. Symmetries and Interactions in Matrix String Theory

    NARCIS (Netherlands)

    Hacquebord, F.H.

    1999-01-01

    This PhD-thesis reviews matrix string theory and recent developments therein. The emphasis is put on symmetries, interactions and scattering processes in the matrix model. We start with an introduction to matrix string theory and a review of the orbifold model that flows out of matrix string theory

  11. Fundamental symmetries and interactions - Some aspects

    NARCIS (Netherlands)

    Jungmann, K

    2005-01-01

    In the framework of nuclear physics and at nuclear physics facilities a large number of different experiments can be performed which render the possibility to investigate fundamental symmetries and interactions in nature. In particular, the precise measurements of properties of fundamental fermions,

  12. Unified flavor symmetry from warped dimensions

    Directory of Open Access Journals (Sweden)

    Mariana Frank

    2015-03-01

    Full Text Available In a model of warped extra-dimensions with all matter fields in the bulk, we propose a scenario which explains all the masses and mixings of the SM fermions. In this scenario, the same flavor symmetric structure is imposed on all the fermions of the Standard Model (SM, including neutrinos. Due to the exponential sensitivity on bulk fermion masses, a small breaking of this symmetry can be greatly enhanced and produce seemingly un-symmetric hierarchical masses and small mixing angles among the charged fermion zero-modes (SM quarks and charged leptons, thus washing out visible effects of the symmetry. If the Dirac neutrinos are sufficiently localized towards the UV boundary, and the Higgs field leaking into the bulk, the neutrino mass hierarchy and flavor structure will still be largely dominated and reflect the fundamental flavor structure, whereas localization of the quark sector would reflect the effects of the flavor symmetry breaking sector. We explore these features in an example based on which a family permutation symmetry is imposed in both quark and lepton sectors.

  13. 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.

  14. Neutrino mass and mixing with discrete symmetry

    Science.gov (United States)

    King, Stephen F.; Luhn, Christoph

    2013-05-01

    This is a review paper about neutrino mass and mixing and flavour model building strategies based on discrete family symmetry. After a pedagogical introduction and overview of the whole of neutrino physics, we focus on the PMNS mixing matrix and the latest global fits following the Daya Bay and RENO experiments which measure the reactor angle. We then describe the simple bimaximal, tri-bimaximal and golden ratio patterns of lepton mixing and the deviations required for a non-zero reactor angle, with solar or atmospheric mixing sum rules resulting from charged lepton corrections or residual trimaximal mixing. The different types of see-saw mechanism are then reviewed as well as the sequential dominance mechanism. We then give a mini-review of finite group theory, which may be used as a discrete family symmetry broken by flavons either completely, or with different subgroups preserved in the neutrino and charged lepton sectors. These two approaches are then reviewed in detail in separate chapters including mechanisms for flavon vacuum alignment and different model building strategies that have been proposed to generate the reactor angle. We then briefly review grand unified theories (GUTs) and how they may be combined with discrete family symmetry to describe all quark and lepton masses and mixing. Finally, we discuss three model examples which combine an SU(5) GUT with the discrete family symmetries A4, S4 and Δ(96).

  15. Configuration-mixed effective SU(3) symmetries

    CERN Document Server

    Hess, P O; Hunyadi, M; Kvi, A G; Cseh, J

    2002-01-01

    The procedure of Jarrio et al. (Nucl. Phys. A 528, 409 (1991)) for the determination of the effective SU(3) symmetry of nuclear states is extended to small deformations and to oblate nuclei. Self-consistency checks are carried out both for light and for heavy nuclei. (orig.)

  16. Anomalous transport effects and possible environmental symmetry ...

    Indian Academy of Sciences (India)

    2015-05-06

    May 6, 2015 ... The heavy-ion collision provides a unique many-body environment where local domains of strongly interacting chiral medium may occur and in a sense allow environmental symmetry 'violation' phenomena. For example, certain anomalous transport processes, forbidden in usual medium, become possible ...

  17. Asymptotic symmetry algebra of conformal gravity

    Science.gov (United States)

    Irakleidou, Maria; Lovrekovic, Iva

    2017-11-01

    We compute asymptotic symmetry algebras of conformal gravity. Due to more general boundary conditions allowed in conformal gravity in comparison to those in Einstein gravity, we can classify the corresponding algebras. The highest algebra for nontrivial boundary conditions is five dimensional and it leads to global geon solution with nonvanishing charges.

  18. Folded Fashions: Symmetry in Clothing Design.

    Science.gov (United States)

    Evered, Lisa J.

    1992-01-01

    Fashion design is a field perceived as both a female and male domain that utilizes mathematics. Presents creative activities to teach the concept of symmetry as applied in fashion designs in the style of the famous French designer Madeleine Vionnet. (MDH)

  19. Symmetry Reduction For Stochastic Hybrid Systems

    NARCIS (Netherlands)

    Bujorianu, L.M.; Katoen, Joost P.

    2008-01-01

    This paper is focused on adapting symmetry reduction, a technique that is highly successful in traditional model checking, to stochastic hybrid systems. To that end, we first show that performability analysis of stochastic hybrid systems can be reduced to a stochastic reachability analysis (SRA).

  20. Symmetry reduction for stochastic hybrid systems

    NARCIS (Netherlands)

    Bujorianu, L.M.; Katoen, Joost P.

    2009-01-01

    This paper is focused on adapting symmetry reduction, a technique that is highly successful in traditional model checking, to stochastic hybrid systems. We first show that performability analysis of stochastic hybrid systems can be reduced to a stochastic reachability analysis (SRA). Then, we

  1. Emergent quantum mechanics and emergent symmetries

    NARCIS (Netherlands)

    Hooft, G. 't

    2007-01-01

    Quantum mechanics is ‘emergent’ if a statistical treatment of large scale phenomena in a locally deterministic theory requires the use of quantum operators. These quantum operators may allow for symmetry transformations that are not present in the underlying deterministic system. Such

  2. Pole Inflation - Shift Symmetry and Universal Corrections

    NARCIS (Netherlands)

    Broy, Benedict J.; Galante, Mario; Roest, Diederik; Westphal, Alexander

    2015-01-01

    An appealing explanation for the Planck data is provided by inflationary models with a singular non-canonical kinetic term: a Laurent expansion of the kinetic function translates into a potential with a nearly shift-symmetric plateau in canonical fields. The shift symmetry can be broken at large

  3. Symmetry Properties of Optimal Relative Orbit Trajectories

    Directory of Open Access Journals (Sweden)

    Mauro Pontani

    2015-01-01

    Full Text Available The determination of minimum-fuel or minimum-time relative orbit trajectories represents a classical topic in astrodynamics. This work illustrates some symmetry properties that hold for optimal relative paths and can considerably simplify their determination. The existence of symmetry properties is demonstrated in the presence of certain boundary conditions for the problems of interest, described by the linear Euler-Hill-Clohessy-Wiltshire equations of relative motion. With regard to minimum-fuel paths, the primer vector theory predicts the existence of several powered phases, divided by coast arcs. In general, the optimal thrust sequence and duration depend on the time evolution of the switching function. In contrast, a minimum-time trajectory is composed of a single continuous-thrust phase. The first symmetry property concerns minimum-fuel and minimum-time orbit paths, both in two and in three dimensions. The second symmetry property regards minimum-fuel relative trajectories. Several examples illustrate the usefulness of these properties in determining minimum-time and minimum-fuel relative paths.

  4. Symmetry and physical properties of crystals

    CERN Document Server

    Malgrange, Cécile; Schlenker, Michel

    2014-01-01

    Crystals are everywhere, from natural crystals (minerals) through the semiconductors and magnetic materials in electronic devices and computers or piezoelectric resonators at the heart of our quartz watches to electro-optical devices. Understanding them in depth is essential both for pure research and for their applications. This book provides a clear, thorough presentation of their symmetry, both at the microscopic space-group level and the macroscopic point-group level. The implications of the symmetry of crystals for their physical properties are then presented, together with their mathematical description in terms of tensors. The conditions on the symmetry of a crystal for a given property to exist then become clear, as does the symmetry of the property. The geometrical representation of tensor quantities or properties is presented, and its use in determining important relationships emphasized. An original feature of this book is that most chapters include exercises with complete solutions. This all...

  5. The Differential Form Method for Finding Symmetries

    Directory of Open Access Journals (Sweden)

    B. Kent Harrison

    2005-08-01

    Full Text Available This article reviews the use of differential forms and Lie derivatives to find symmetries of differential equations, as originally presented in Harrison and Estabrook, J. Math. Phys., 12 (1971, 653. An outline of the method is given, followed by examples and references to recent papers using the method.

  6. Cobimaximal lepton mixing from soft symmetry breaking

    Directory of Open Access Journals (Sweden)

    W. Grimus

    2017-11-01

    Full Text Available 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.

  7. Symplectic symmetry in the nuclear shell model

    NARCIS (Netherlands)

    French, J.B.

    The nature of the general two-particle interaction which is compatible with symplectic symmetry in the jj coupling shell model is investigated. The essential result is that, to within an additive constant and an additive multiple of T2, the interaction should have the form of a sum of scalar

  8. Introduction to chiral symmetry in QCD

    Directory of Open Access Journals (Sweden)

    Sazdjian H.

    2017-01-01

    Full Text Available The main aspects of chiral symmetry in QCD are presented. The necessity of its spontaneous breakdown is explained. Some low-energy theorems are reviewed. The role of chiral effective Lagrangians in the formulation and realization of chiral perturbation theory is emphasized. The consequences of the presence of anomalies are sketched.

  9. Maintaining symmetry of simulated likelihood functions

    DEFF Research Database (Denmark)

    Andersen, Laura Mørch

    This paper suggests solutions to two different types of simulation errors related to Quasi-Monte Carlo integration. Likelihood functions which depend on standard deviations of mixed parameters are symmetric in nature. This paper shows that antithetic draws preserve this symmetry and thereby...

  10. Systematic model building with flavor symmetries

    Energy Technology Data Exchange (ETDEWEB)

    Plentinger, Florian

    2009-12-19

    The observation of neutrino masses and lepton mixing has highlighted the incompleteness of the Standard Model of particle physics. In conjunction with this discovery, new questions arise: why are the neutrino masses so small, which form has their mass hierarchy, why is the mixing in the quark and lepton sectors so different or what is the structure of the Higgs sector. In order to address these issues and to predict future experimental results, different approaches are considered. One particularly interesting possibility, are Grand Unified Theories such as SU(5) or SO(10). GUTs are vertical symmetries since they unify the SM particles into multiplets and usually predict new particles which can naturally explain the smallness of the neutrino masses via the seesaw mechanism. On the other hand, also horizontal symmetries, i.e., flavor symmetries, acting on the generation space of the SM particles, are promising. They can serve as an explanation for the quark and lepton mass hierarchies as well as for the different mixings in the quark and lepton sectors. In addition, flavor symmetries are significantly involved in the Higgs sector and predict certain forms of mass matrices. This high predictivity makes GUTs and flavor symmetries interesting for both, theorists and experimentalists. These extensions of the SM can be also combined with theories such as supersymmetry or extra dimensions. In addition, they usually have implications on the observed matter-antimatter asymmetry of the universe or can provide a dark matter candidate. In general, they also predict the lepton flavor violating rare decays {mu} {yields} e{gamma}, {tau} {yields} {mu}{gamma}, and {tau} {yields} e{gamma} which are strongly bounded by experiments but might be observed in the future. In this thesis, we combine all of these approaches, i.e., GUTs, the seesaw mechanism and flavor symmetries. Moreover, our request is to develop and perform a systematic model building approach with flavor symmetries and

  11. Asymptotic symmetries, holography and topological hair

    Science.gov (United States)

    Mishra, Rashmish K.; Sundrum, Raman

    2018-01-01

    Asymptotic symmetries of AdS4 quantum gravity and gauge theory are derived by coupling the holographically dual CFT3 to Chern-Simons gauge theory and 3D gravity in a "probe" (large-level) limit. Despite the fact that the three-dimensional AdS4 boundary as a whole is consistent with only finite-dimensional asymptotic symmetries, given by AdS isometries, infinite-dimensional symmetries are shown to arise in circumstances where one is restricted to boundary subspaces with effectively two-dimensional geometry. A canonical example of such a restriction occurs within the 4D subregion described by a Wheeler-DeWitt wavefunctional of AdS4 quantum gravity. An AdS4 analog of Minkowski "super-rotation" asymptotic symmetry is probed by 3D Einstein gravity, yielding CFT2 structure (in a large central charge limit), via AdS3 foliation of AdS4 and the AdS3/CFT2 correspondence. The maximal asymptotic symmetry is however probed by 3D conformal gravity. Both 3D gravities have Chern-Simons formulation, manifesting their topological character. Chern-Simons structure is also shown to be emergent in the Poincare patch of AdS4, as soft/boundary limits of 4D gauge theory, rather than "put in by hand" as an external probe. This results in a finite effective Chern-Simons level. Several of the considerations of asymptotic symmetry structure are found to be simpler for AdS4 than for Mink4, such as non-zero 4D particle masses, 4D non-perturbative "hard" effects, and consistency with unitarity. The last of these in particular is greatly simplified because in some set-ups the time dimension is explicitly shared by each level of description: Lorentzian AdS4, CFT3 and CFT2. Relatedly, the CFT2 structure clarifies the sense in which the infinite asymptotic charges constitute a useful form of "hair" for black holes and other complex 4D states. An AdS4 analog of Minkowski "memory" effects is derived, but with late-time memory of earlier events being replaced by (holographic) "shadow" effects. Lessons

  12. An acoustic eikonal equation for attenuating transversely isotropic media with a vertical symmetry axis

    KAUST Repository

    Hao, Qi

    2016-11-21

    Seismic-wave attenuation is an important component of describing wave propagation. Certain regions, such as gas clouds inside the earth, exert highly localized attenuation. In fact, the anisotropic nature of the earth induces anisotropic attenuation because the quasi P-wave dispersion effect should be profound along the symmetry direction. We have developed a 2D acoustic eikonal equation governing the complex-valued traveltime of quasi P-waves in attenuating, transversely isotropic media with a vertical-symmetry axis (VTI). This equation is derived under the assumption that the complex-valued traveltime of quasi P-waves in attenuating VTI media are independent of the S-wave velocity parameter υS0 in Thomsen\\'s notation and the S-wave attenuation coefficient AS0 in Zhu and Tsvankin\\'s notation. We combine perturbation theory and Shanks transform to develop practical approximations to the acoustic attenuating eikonal equation, capable of admitting an analytical description of the attenuation in homogeneous media. For a horizontal-attenuating VTI layer, we also derive the nonhyperbolic approximations for the real and imaginary parts of the complex-valued reflection traveltime. These equations reveal that (1) the quasi SV-wave velocity and the corresponding quasi SV-wave attenuation coefficient given as part of Thomsen-type notation barely affect the ray velocity and ray attenuation of quasi P-waves in attenuating VTI media; (2) combining the perturbation method and Shanks transform provides an accurate analytic eikonal solution for homogeneous attenuating VTI media; (3) for a horizontal attenuating VTI layer with weak attenuation, the real part of the complex-valued reflection traveltime may still be described by the existing nonhyperbolic approximations developed for nonattenuating VTI media, and the imaginary part of the complex-valued reflection traveltime still has the shape of nonhyperbolic curves. In addition, we have evaluated the possible extension of the

  13. Robust topology optimization of three-dimensional photonic-crystal band-gap structures.

    Science.gov (United States)

    Men, H; Lee, K Y K; Freund, R M; Peraire, J; Johnson, S G

    2014-09-22

    We perform full 3D topology optimization (in which "every voxel" of the unit cell is a degree of freedom) of photonic-crystal structures in order to find optimal omnidirectional band gaps for various symmetry groups, including fcc (including diamond), bcc, and simple-cubic lattices. Even without imposing the constraints of any fabrication process, the resulting optimal gaps are only slightly larger than previous hand designs, suggesting that current photonic crystals are nearly optimal in this respect. However, optimization can discover new structures, e.g. a new fcc structure with the same symmetry but slightly larger gap than the well known inverse opal, which may offer new degrees of freedom to future fabrication technologies. Furthermore, our band-gap optimization is an illustration of a computational approach to 3D dispersion engineering which is applicable to many other problems in optics, based on a novel semidefinite-program formulation for nonconvex eigenvalue optimization combined with other techniques such as a simple approach to impose symmetry constraints. We also demonstrate a technique for robust topology optimization, in which some uncertainty is included in each voxel and we optimize the worst-case gap, and we show that the resulting band gaps have increased robustness to systematic fabrication errors.

  14. Broken-Symmetry States and Divergent Resistance in Suspended Bilayer Graphene

    Science.gov (United States)

    Feldman, Benjamin; Martin, Jens; Weitz, Thomas; Allen, Monica; Yacoby, Amir

    2010-03-01

    We report the fabrication of suspended bilayer graphene devices with very little disorder. Transport measurements at zero magnetic field indicate that charge inhomogeneity in these flakes reaches as low as 10^10 cm-2. We observe quantum Hall states that are fully quantized at a magnetic field of 0.2 T, as well as broken-symmetry states at intermediate filling factors ν = 0, ±1, ±2 and ±3. In the ν = 0 state, the resistance of the flakes increases exponentially with applied magnetic field and scales as magnetic field divided by temperature. This resistance is predominantly affected by the perpendicular component of the applied field and the extracted gap size is larger than expected from Zeeman splitting, indicating that the broken-symmetry states arise from many-body interactions and underscoring the importance of Coulomb interactions in bilayer graphene.

  15. 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.

  16. Conservation laws and symmetries for a nonholonomic deformed Volterra equation

    Energy Technology Data Exchange (ETDEWEB)

    Xia Baoqiang; Zhou Ruguang, E-mail: xiabaoqiang@126.com, E-mail: rgzhou@public.xz.js.cn [School of Mathematical Sciences, Xuzhou Normal University, Xuzhou 221116 (China)

    2011-08-05

    A nonholonomic deformed Volterra equation is studied. Its Lax representation, infinitely many of conservation laws and generalized commutation symmetries are given. A degenerate recursion operator to generate the generalized symmetries is proposed.

  17. Symmetry-protected topological phases, generalized Laughlin argument, and orientifolds

    Science.gov (United States)

    Hsieh, Chang-Tse; Sule, Olabode Mayodele; Cho, Gil Young; Ryu, Shinsei; Leigh, Robert G.

    2014-10-01

    We generalize Laughlin's flux insertion argument, originally discussed in the context of the quantum Hall effect, to topological phases protected by non-on-site unitary symmetries, in particular by parity symmetry or parity symmetry combined with an on-site unitary symmetry. As a model, we discuss fermionic or bosonic systems in two spatial dimensions with CP symmetry, which are, by the CPT theorem, related to time-reversal symmetric topological insulators (e.g., the quantum spin Hall effect). In particular, we develop the stability/instability (or "gappability"/"ingappablity") criteria for nonchiral conformal field theories with parity symmetry that may emerge as an edge state of a symmetry-protected topological phase. A necessary ingredient, as it turns out, is to consider the edge conformal field theories on unoriented surfaces, such as the Klein bottle, which arises naturally from enforcing parity symmetry by a projection operation.

  18. Noether symmetry approach in f ( R ) –tachyon model

    National Research Council Canada - National Science Library

    Jamil, Mubasher; Mahomed, F.M; Momeni, D

    2011-01-01

    In this Letter by utilizing the Noether symmetry approach in cosmology, we attempt to find the tachyon potential via the application of this kind of symmetry to a flat Friedmann-Robertson-Walker (FRW) metric...

  19. On PT Symmetry Systems: Invariance, Conservation Laws, and Reductions

    Directory of Open Access Journals (Sweden)

    P. Masemola

    2014-01-01

    results in a scalar cubic Schrödinger equation. We investigate the relationship between the conservation laws and Lie symmetries and investigate a Lagrangian, corresponding Noether symmetries, conserved vectors, and exact solutions via “double reductions.”

  20. 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.

  1. Symmetry and symmetry breaking in quantum mechanics; Symetrie et brisure de symetrie en mechanique quantique

    Energy Technology Data Exchange (ETDEWEB)

    Chomaz, Philippe [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France)

    1998-12-31

    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 17 refs., 16 figs.

  2. Photonic band gaps in materials with triply periodic surfaces and related tubular structures

    NARCIS (Netherlands)

    Michielsen, K; Kole, JS

    2003-01-01

    We calculate the photonic band gap of triply periodic bicontinuous cubic structures and of tubular structures constructed from the skeletal graphs of triply periodic minimal surfaces. The effect of the symmetry and topology of the periodic dielectric structures on the existence and the

  3. An Objective Rationale for the Choice of Regularisation Parameter with Application to Global Multiple-Frequency S-Wave Tomography

    Science.gov (United States)

    Zaroli, C.; Sambridge, M.; Leveque, J. J.; Debayle, E.; Nolet, G.

    2014-12-01

    In a linear ill-posed inverse problem, the regularisation parameter (damping) controls the balance between minimising both the residual data misfit and the model norm. Poor knowledge of data uncertainties often makes the selection of damping rather arbitrary. To go beyond that subjectivity, an objective rationale for the choice of damping is presented, which is based on the coherency of delay-time estimates in different frequency bands. Our method is tailored to the problem of global Multiple-Frequency Tomography, using a data set of 287078 S-wave delay-times measured in five frequency bands (10, 15, 22, 34, 51 s central periods). Whereas for each ray path the delay-time estimates should vary coherently from one period to the other, the noise most likely is not coherent. Thus, the lack of coherency of the information in different frequency bands is exploited, using an analogy with the cross-validation method, to identify models dominated by noise.In addition, a sharp change of behaviour of the model infinity-norm, as the damping becomes lower than a threshold value, is interpreted as the signature of data noise starting to significantly pollute at least one model component. Models with damping larger than this threshold are diagnosed as being constructed with poor data exploitation.Finally, a preferred model is selected from the remaining range of permitted model solutions. This choice is quasi-objective in terms of model interpretation, as the selected model shows a high degree of similarity with almost all other permitted models. The obtained tomographic model is displayed in mid lower-mantle (660-1910 km depth), and is shown to be mostly compatible with three other recent global shear-velocity models, while significant differences can be noticed. A wider application of the presented rationale should permit us to converge towards more objective seismic imaging of the Earth's mantle, using as much as possible of the relevant structural information in the data

  4. A Bayesian approach to the real-time estimation of magnitude from the early P and S wave displacement peaks

    Science.gov (United States)

    Lancieri, M.; Zollo, A.

    2008-12-01

    It has been shown that the initial portion of P and S wave signals can provide information about the final earthquake magnitude in a wide magnitude range. This observation opens the perspective for the real-time determination of source parameters. In this paper we describe a probabilistic evolutionary approach for the real-time magnitude estimation which can have a potential use in earthquake early warning. The technique is based on empirical prediction laws correlating the low-frequency peak ground displacement measured in a few seconds after the P and/or S phase arrival and the final event magnitude. The evidence for such a correlation has been found through the analysis of 256 shallow crustal events in the magnitude range Mjma 4-7.1 located over the entire Japanese archipelago. The peak displacement measured in a 2-s window from the first P phase arrival correlates with magnitude in the range M = [4-6.5]. While a possible saturation effect above M ≃ 6.5 is observed, it is less evident in an enlarged window of 4 s. The scaling of S peaks with magnitude is instead also observed at smaller time lapses (i.e., 1 s) after the first S arrival. The different scaling of P and S peaks with magnitude when measured in a 2-s window is explained in terms of different imaged rupture surface by the early portion of the body wave signals. We developed a technique to estimate the probability density function (PDF) of magnitude, at each time step after the event origin. The predicted magnitude value corresponds to the maximum of PDF, while its uncertainty is given by the 95% confidence bound. The method has been applied to the 2007 (Mjma = 6.9) Noto Hanto and 1995 (Mjma = 7.3) Kobe earthquakes. The results of this study can be summarized as follows: (1) The probabilistic algorithm founded on the predictive model of peak displacement versus final magnitude is able to provide a fast and robust estimation of the final magnitude. (2) The information available after a few seconds

  5. Upper mantle seismic structure beneath southwest Africa from finite-frequency P- and S-wave tomography

    Science.gov (United States)

    Youssof, Mohammad; Yuan, Xiaohui; Tilmann, Frederik; Heit, Benjamin; Weber, Michael; Jokat, Wilfried; Geissler, Wolfram; Laske, Gabi; Eken, Tuna; Lushetile, Bufelo

    2015-04-01

    We present a 3D high-resolution seismic model of the southwestern Africa region from teleseismic tomographic inversion of the P- and S- wave data recorded by the amphibious WALPASS network. We used 40 temporary stations in southwestern Africa with records for a period of 2 years (the OBS operated for 1 year), between November 2010 and November 2012. The array covers a surface area of approximately 600 by 1200 km and is located at the intersection of the Walvis Ridge, the continental margin of northern Namibia, and extends into the Congo craton. Major questions that need to be understood are related to the impact of asthenosphere-lithosphere interaction, (plume-related features), on the continental areas and the evolution of the continent-ocean transition that followed the break-up of Gondwana. This process is supposed to leave its imprint as distinct seismic signature in the upper mantle. Utilizing 3D sensitivity kernels, we invert traveltime residuals to image velocity perturbations in the upper mantle down to 1000 km depth. To test the robustness of our tomographic image we employed various resolution tests which allow us to evaluate the extent of smearing effects and help defining the optimum inversion parameters (i.e., damping and smoothness) used during the regularization of inversion process. Resolution assessment procedure includes also a detailed investigation of the effect of the crustal corrections on the final images, which strongly influenced the resolution for the mantle structures. We present detailed tomographic images of the oceanic and continental lithosphere beneath the study area. The fast lithospheric keel of the Congo Craton reaches a depth of ~250 km. Relatively low velocity perturbations have been imaged within the orogenic Damara Belt down to a depth of ~150 km, probably related to surficial suture zones and the presence of fertile material. A shallower depth extent of the lithospheric plate of ~100 km was observed beneath the ocean

  6. Sub-thermal to super-thermal light statistics from a disordered lattice via deterministic control of excitation symmetry

    CERN Document Server

    Kondakci, H E; Abouraddy, A F; Christodoulides, D N; Saleh, B E A

    2016-01-01

    Monochromatic coherent light traversing a disordered photonic medium evolves into a random field whose statistics are dictated by the disorder level. Here we demonstrate experimentally that light statistics can be deterministically tuned in certain disordered lattices, even when the disorder level is held fixed, by controllably breaking the excitation symmetry of the lattice modes. We exploit a lattice endowed with disorder-immune chiral symmetry in which the eigenmodes come in skew-symmetric pairs. If a single lattice site is excited, a "photonic thermalization gap" emerges: the realm of sub-thermal light statistics is inaccessible regardless of the disorder level. However, by exciting two sites with a variable relative phase, as in a traditional two-path interferometer, the chiral symmetry is judiciously broken and interferometric control over the light statistics is exercised, spanning sub-thermal and super-thermal regimes. These results may help develop novel incoherent lighting sources from coherent lase...

  7. Note on the Lattice Fermion Chiral Symmetry Group

    OpenAIRE

    Mandula, Jeffrey E.

    2007-01-01

    The group structure of the variant chiral symmetry discovered by Luscher in the Ginsparg-Wilson description of lattice chiral fermions is analyzed. It is shown that the group contains an infinite number of linearly independent symmetry generators, and the Lie algebra is given explicitly. CP is an automorphism of the chiral group, and the CP transformation properties of the symmetry generators is found. Features of the currents associated with these symmetries are discussed, including the fact...

  8. 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.

  9. Translation-symmetry protected topological orders on lattice

    OpenAIRE

    Kou, Su-Peng; Wen, Xiao-Gang

    2009-01-01

    In this paper we systematically study a simple class of translation-symmetry protected topological orders in quantum spin systems using slave-particle approach. The spin systems on square lattice are translation invariant, but may break any other symmetries. We consider topologically ordered ground states that do not spontaneously break any symmetry. Those states can be described by Z2A or Z2B projective symmetry group. We find that the Z2A translation symmetric topological orders can still b...

  10. Symmetries, supersymmetries and cohomologies in gauge theories

    Science.gov (United States)

    Bǎbǎlîc, Elena-Mirela

    2009-12-01

    The main subjects approached in the thesis are the following: a) the derivation of the interactions in two space-time dimensions in a particular class of topological BF models; b) the construction of the couplings in D ≥ 5 dimensions between one massless tensor field with the mixed symmetry (3, 1) and one with the mixed symmetry of the Riemann tensor; c) the evaluation of the existence of interactions in D ≥ 5 dimensions between two different collections of massless tensor fields with the mixed symmetries (3, 1) and (2, 2); d) the analysis of the relation between the BRST charges obtained in the pure-spinor formalism, respectively in the κ-symmetric one for the supermembrane in eleven dimensions. Our procedure for the first three subjects is based on solving the equations that describe the deformation of the solution to the master equation by means of specific cohomological techniques, while for the fourth one we will use techniques specific to the BRST Hamiltonian approach in order to write the BRST charge. The interactions are obtained under the following hypotheses: locality, Lorentz covariance, Poincare invariance, analyticity of the deformations, and preservation of the number of derivatives on each field. The first three assumptions imply that the interacting theory is local in space-time, Lorentz covariant and Poincare invariant. The analyticity of the deformations refers to the fact that the deformed solution to the master equation is analytical in the coupling constant and reduces to the original solution in the free limit. The conservation of the number of derivatives on each field with respect to the free theory means here that the following two requirements are simultaneously satisfied: (i) the derivative order of the equations of motion on each field is the same for the free and respectively for the interacting theory; (ii) the maximum number of derivatives in the interaction vertices is equal to two, i.e. the maximum number of derivatives from

  11. Locating S-wave sources for the SPE-5 explosion using time reversal methods and a close-in, 1000 sensor network

    Science.gov (United States)

    Myers, S. C.; Pitarka, A.; Mellors, R. J.

    2016-12-01

    The Source Physics Experiment (SPE) is producing new data to study the generation of seismic waves from explosive sources. Preliminary results show that far-field S-waves are generated both within the non-elastic volume surrounding explosive sources and by P- to S-wave scattering. The relative contribution of non-elastic phenomenology and elastic-wave scattering to far-field S-waves has been debated for decades, and numerical simulations based on the SPE experiments are addressing this question. The match between observed and simulated data degrades with event-station distance and with increasing time in each seismogram. This suggests that a more accurate model of subsurface elastic properties could result in better agreement between observed and simulated seismograms. A detailed model of subsurface structure has been developed using geologic maps and the extensive database of borehole logs, but uncertainty in structural details remains high. The large N instrument deployment during the SPE-5 experiment offers an opportunity to use time-reversal techniques to back project the wave field into the subsurface to locate significant sources of scattered energy. The large N deployment was nominally 1000, 5 Hz sensors (500 Z and 500 3C geophones) deployed in a roughly rectangular array to the south and east of the SPE-5 shot. Sensor spacing was nominally 50 meters in the interior portion of the array and 100 meters in the outer region, with two dense lines at 25 m spacing. The array covers the major geologic boundary between the Yucca Flat basin and the granitic Climax Stock in which the SPE experiments have been conducted. Improved mapping of subsurface scatterers is expected to result in better agreement between simulated and observed seismograms and aid in our understanding of S-wave generation from explosions. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

  12. Geological variation in S-wave velocity structures in Northern Taiwan and implications for seismic hazards based on ambient noise analysis

    Science.gov (United States)

    Lai, Ya-Chuan; Huang, Bor-Shouh; Huang, Yu-Chih; Yao, Huajian; Hwang, Ruey-Der; Huang, Yi-Ling; Chang, Wen-Yen

    2014-12-01

    Ambient noise analysis in Northern Taiwan revealed obvious lateral variations related to major geological units. The empirical Green's functions extracted from interstation ambient noise were regarded as Rayleigh waves, from which we analyzed the group velocities for period from 3 to 6 s. According to geological features, we divided Northern Taiwan into seven subregions, for which regionalized group velocities were derived by using the pure-path method. On average, the group velocities in mountain areas were higher than those in the plain areas. We subsequently inverted the S-wave velocity structure for each subregion down to 6 km in depth. Following the analysis, we proposed the first models of geology-dependent shallow S-wave structures in Northern Taiwan. Overall, the velocity increased substantially from west to east; specifically, the mountain areas, composed of metamorphic rocks, exhibited higher velocities than did the coastal plain and basin, which consist of soft sediment. At a shallow depth, the Western Coastal Plain, Taipei Basin, and Ilan Plain displayed a larger velocity gradient than did other regions. At the top 3 km of the model, the average velocity gradient was 0.39 km/s per km for the Western Coastal Plain and 0.15 km/s per km for the Central Range. These S-wave velocity models with large velocity gradients caused the seismic waves to become trapped easily in strata and, thus, the ground motion was amplified. The regionalized S-wave velocity models derived from ambient noises can provide useful information regarding seismic wave propagation and for assessing seismic hazards in Northern Taiwan.

  13. Consistencies far beyond chance: an analysis of learner preconceptions of reflective symmetry

    Directory of Open Access Journals (Sweden)

    Michael Kainose Mhlolo

    2013-01-01

    Full Text Available This article reports on regularities observed in learners' preconceptions of reflective symmetry. Literature suggests that the very existence of such regularities indicates a gap between what learners know and what they need to know. Such a gap inhibits further understanding and application, and hence needed to be investigated. A total of 235 Grade 11 learners, from 13 high schools that participate in the First Rand Foundation-funded Mathematics Education project in the Eastern Cape, responded to a task on reflective symmetry. Our framework for analysing the responses was based on the taxonomy of structure of the observed learning outcome. The results indicated that 85% of learner responses reflect a motion understanding of reflections, where learners considered geometric figures as physical motions on top of the plane. While this understanding is useful in some cases, it is not an essential aspect of mapping understanding, which is critical for application in function notations and other analytical geometry contexts. We suggest that if this gap is to be closed, learners need to construct these reflections physically so that they may think of reflections beyond motion.

  14. Probing the density content of the nuclear symmetry energy

    Indian Academy of Sciences (India)

    Abstract. The nature of equation of state for the neutron star matter is crucially governed by the density dependence of the nuclear symmetry energy. We attempt to probe the behaviour of the nuclear symmetry energy around the saturation density by exploiting the empirical values for volume and surface symmetry energy ...

  15. Symmetries and conservation laws of the damped harmonic oscillator

    Indian Academy of Sciences (India)

    We work with a formulation of Noether-symmetry analysis which uses the properties of infinitesimal point transformations in the space-time variables to establish the association between symmetries and conservation laws of a dynamical system. Here symmetries are expressed in the form of generators. We have studied the ...

  16. On the symmetry of phosphorous doped ZnSe

    Indian Academy of Sciences (India)

    The site symmetry of P doped ZnSe is analysed in detail here, as the recent experiments suggest two possible symmetries T d and C 3 V . The reduction to C 3 V is attributed to the presence of natural impurity, Ga. Our calculations based on molecular model and Green's functions suggest that the symmetry C 3 V is possible ...

  17. Symmetry Concerns as a Symptom of Body Dysmorphic Disorder.

    Science.gov (United States)

    Hart, Ashley S; Phillips, Katharine A

    2013-07-01

    Symmetry obsessions are a common symptom of obsessive-compulsive disorder (OCD) and have several demographic and clinical correlates. Appearance-related symmetry concerns appear common in body dysmorphic disorder (BDD); however, no published studies have examined this topic. This study examined the clinical features, prevalence, and correlates of symmetry concerns involving physical appearance in two BDD samples (N=160 and N=115). More than 25% of participants in each sample reported symmetry concerns for a body part with which they were preoccupied (total of 18 body parts in sample 1 and 18 in sample 2). In sample 1, BDD participants with appearance-related symmetry concerns were older than those without appearance-related symmetry concerns. In sample 2, those with appearance-related symmetry concerns reported poorer mental health-related quality of life, were more likely to have experienced lifetime suicidal ideation, had better BDD-related insight, and were less likely to have a lifetime eating disorder. In both samples, participants with appearance-related symmetry concerns were more likely to have lifetime OCD but not OCD-related symmetry obsessions. Thus, symmetry is a common appearance concern in BDD that is associated with comorbid OCD but not with OCD symmetry concerns specifically, suggesting that symmetry concerns may have a different mechanism/pathophysiology in BDD versus OCD.

  18. Approximate Noether gauge symmetries of the Bardeen model

    Energy Technology Data Exchange (ETDEWEB)

    Camci, U. [Akdeniz University, Department of Physics, Faculty of Science, Antalya (Turkey)

    2014-12-01

    We investigate the approximate Noether gauge symmetries of the geodesic Lagrangian for the Bardeen spacetime model. This is accommodated by a set of new approximate Noether gauge symmetry relations for the perturbed geodesic Lagrangian in the spacetime. A detailed analysis of the spacetime of the Bardeen model up to third-order approximate Noether gauge symmetries is presented. (orig.)

  19. Symmetries and conservation laws of the damped harmonic oscillator

    Indian Academy of Sciences (India)

    Abstract. We work with a formulation of Noether-symmetry analysis which uses the properties of infinitesimal point transformations in the space-time variables to establish the association between symmetries and conservation laws of a dynamical system. Here symmetries are expressed in the form of generators. We have ...

  20. On the symmetry of phosphorous doped ZnSe

    Indian Academy of Sciences (India)

    Unknown

    The site symmetry of P doped ZnSe is analysed in detail here, as the recent experiments suggest two possible symmetries ... ZnSe; localized vibrational modes; Td and C3V symmetries; Jahn Teller distortion; Green's func- tion; molecular model. 1. ..... central and non central forces into account (Plummelle and Vandevyver ...

  1. S-wave attenuation in northeastern Sonora, Mexico, near the faults that ruptured during the earthquake of 3 May 1887 Mw 7.5.

    Science.gov (United States)

    Villalobos-Escobar, Gina P; Castro, Raúl R

    2014-01-01

    We used a new data set of relocated earthquakes recorded by the Seismic Network of Northeastern Sonora, Mexico (RESNES) to characterize the attenuation of S-waves in the fault zone of the 1887 Sonora earthquake (M w 7.5). We determined spectral attenuation functions for hypocentral distances (r) between 10 and 140 km using a nonparametric approach and found that in this fault zone the spectral amplitudes decay slower with distance at low frequencies (f attenuation functions obtained for 23 frequencies (0.4 ≤ f ≤ 63.1 Hz) permit us estimating the average quality factor Q S  = (141 ± 1.1 )f ((0.74 ± 0.04)) and a geometrical spreading term G(r) = 1/r (0.21). The values of Q estimated for S-wave paths traveling along the fault system that rupture during the 1887 event, in the north-south direction, are considerably lower than the average Q estimated using source-station paths from multiple stations and directions. These results indicate that near the fault zone S waves attenuate considerably more than at regional scale, particularly at low frequencies. This may be the result of strong scattering near the faults due to the fractured upper crust and higher intrinsic attenuation due to stress concentration near the faults.

  2. Automatic detection of P- and S-wave arrival times: new strategies based on the modified fractal method and basic matching pursuit

    Science.gov (United States)

    Chi-Durán, Rodrigo; Comte, Diana; Díaz, Marcos; Silva, Jorge F.

    2017-09-01

    In this work, new strategies for automatic identification of P- and S-wave arrival times from digital recorded local seismograms are proposed and analyzed. The database of arrival times previously identified by a human reader was compared with automatic identification techniques based on the Fourier transformation in reduced time (spectrograms), fractal analysis, and the basic matching pursuit algorithm. The first two techniques were used to identify the P-wave arrival times, while the third was used for the identification of the S-wave. For validation, the results were compared with the short-time average over long-time average (STA/LTA) of Rietbrock et al., Geophys Res Lett 39(8), (2012) for the database of aftershocks of the 2010 Maule M w = 8.8 earthquake. The identifiers proposed in this work exhibit good results that outperform the STA/LTA identifier in many scenarios. The average difference from the reference picks (times obtained by the human reader) in P- and S-wave arrival times is ˜ 1 s.

  3. Comparison of an empirical S-wave velocity model and a calculated stress-strain model for a rock mass disturbed by mining

    Science.gov (United States)

    Krawiec, Krzysztof; Czarny, Rafał

    2017-11-01

    In the article a comparison analysis is presented between a numerical model of the stress and deformation state in a rock mass and an S-wave velocity model obtained as a result of in situ measurement. The research was conducted using data from the Jastrzębie and Moszczenica coal mines. The part of the rock mass examined was strongly disturbed by multi-seam exploitation of coal. To obtain the S-wave velocity model 6 hours of ambient seismic noise data were recorded using 11 seismometers. The propagation of the Rayleigh surface wave between the seismometers was reconstructed utilising the seismic interferometry and the cross correlation technique. Estimation of a two dimensional model of the Swave velocity field was performed on the basis of dispersion curves of the Rayleigh wave phase velocity. The stress and deformation field were calculated assuming a plane state of stress with the use of the elastic-plastic Coulomb-Mohr strength criterion. Images of the vertical stress, horizontal stress, vertical strain and horizontal strain as well as the subsidence profile on the model surface were obtained as a result of the calculation. Analysis of the results shows correlation between the field of S-wave velocity and the modelled field of stress and strain.

  4. Comparison of an empirical S-wave velocity model and a calculated stress-strain model for a rock mass disturbed by mining

    Directory of Open Access Journals (Sweden)

    Krawiec Krzysztof

    2017-01-01

    Full Text Available In the article a comparison analysis is presented between a numerical model of the stress and deformation state in a rock mass and an S-wave velocity model obtained as a result of in situ measurement. The research was conducted using data from the Jastrzębie and Moszczenica coal mines. The part of the rock mass examined was strongly disturbed by multi-seam exploitation of coal. To obtain the S-wave velocity model 6 hours of ambient seismic noise data were recorded using 11 seismometers. The propagation of the Rayleigh surface wave between the seismometers was reconstructed utilising the seismic interferometry and the cross correlation technique. Estimation of a two dimensional model of the Swave velocity field was performed on the basis of dispersion curves of the Rayleigh wave phase velocity. The stress and deformation field were calculated assuming a plane state of stress with the use of the elastic-plastic Coulomb-Mohr strength criterion. Images of the vertical stress, horizontal stress, vertical strain and horizontal strain as well as the subsidence profile on the model surface were obtained as a result of the calculation. Analysis of the results shows correlation between the field of S-wave velocity and the modelled field of stress and strain.

  5. Mass gap without confinement

    Science.gov (United States)

    Faedo, Antón F.; Mateos, David; Pravos, David; Subils, Javier G.

    2017-06-01

    We revisit a one-parameter family of three-dimensional gauge theories with known supergravity duals. We show that three infrared behaviors are possible. For generic values of the parameter, the theories exhibit a mass gap but no confinement, meaning no linear quark-antiquark potential; for one limiting value of the parameter the theory flows to an infrared fixed point; and for another limiting value it exhibits both a mass gap and confinement. Theories close to these limiting values exhibit quasi-conformal and quasi-confining dynamics, respectively. Eleven-dimensional supergravity provides a simple, geometric explanation of these features.

  6. The longevity gender gap

    DEFF Research Database (Denmark)

    Aviv, Abraham; Shay, Jerry; Christensen, Kaare

    2005-01-01

    resistant to the ravages of time. We discuss the interplay of these factors with telomere biology and oxidative stress and suggest that an explanation for the longevity gender gap may arise from a better understanding of the differences in telomere dynamics between men and women.......In this Perspective, we focus on the greater longevity of women as compared with men. We propose that, like aging itself, the longevity gender gap is exceedingly complex and argue that it may arise from sex-related hormonal differences and from somatic cell selection that favors cells more...

  7. Bridging the Emissions Gap

    OpenAIRE

    Blok, K.

    2012-01-01

    The analyses in Chapters 2 and 3 of this report concluded that the emissions gap in 2020 will likely be between 8 and 13 GtCO2e. The chapters also estimated the difference between BaU emissions in 2020 and the emissions level consistent with a “likely” chance of staying within the 2°C target to be 14 GtCO2e. This chapter explores the potential for bridging this gap using a sector policy approach. Firstly, the chapter provides a summary and update of the estimated emission reduction potential ...

  8. Ratchet device with broken friction symmetry

    DEFF Research Database (Denmark)

    Norden, Bengt; Zolotaryuk, Yaroslav; Christiansen, Peter Leth

    2002-01-01

    An experimental setup (gadget) has been made for demonstration of a ratchet mechanism induced by broken symmetry of a dependence of dry friction on external forcing. This gadget converts longitudinal oscillating or fluctuating motion into a unidirectional rotation, the direction of which is in ac...... is in accordance with given theoretical arguments. Despite the setup being three dimensional, the ratchet rotary motion is proved to be described by one simple dynamic equation. This kind of motion is a result of the interplay of friction and inertia.......An experimental setup (gadget) has been made for demonstration of a ratchet mechanism induced by broken symmetry of a dependence of dry friction on external forcing. This gadget converts longitudinal oscillating or fluctuating motion into a unidirectional rotation, the direction of which...

  9. Black hole entropy calculations based on symmetries

    CERN Document Server

    Dreyer, O; Wísniewski, J A; Dreyer, Olaf; Ghosh, Amit; Wisniewski, Jacek

    2001-01-01

    Symmetry based approaches to the black hole entropy problem have a number of attractive features; in particular they are very general and do not depend on the details of the quantization method. However we point out that, of the two available approaches, one faces conceptual problems (also emphasized by others), while the second contains certain technical flaws. We correct these errors and, within the new, improved scheme, calculate the entropy of 3-dimensional black holes. We find that, while the new symmetry vector fields are well-defined on the ``stretched horizon,'' and lead to well-defined Hamiltonians satisfying the expected Lie algebra, they fail to admit a well-defined limit to the horizon. This suggests that, although the formal calculation can be carried out at the classical level, its real, conceptual origin probably lies in the quantum theory.

  10. State of Modeling Symmetry in Hohlraums

    Energy Technology Data Exchange (ETDEWEB)

    Jones, O. S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-07-22

    Modeling radiation drive asymmetry is challenging problem whose agreement with data depends on the hohlraum gas fill density. Modeling to date uses the HYDRA code with crossbeam energy transfer (CBET) calculated separately, and backscattered light removed from the input laser. For high fill hohlraums (~>1 mg/cc), matching symmetry requires ad hoc adjustments to CBET during picket and peak of drive. For near-vacuum hohlraums, there is little CBET or backscatter, and drive is more waist-high than predicted. For intermediate fill densities (~0.6 mg/cc) there appears to be a region of small CBET and backscatter where symmetry is reasonably well modeled. A new technique where backscatter and CBET are done “inline” appears it could bring high fill simulations closer to data.

  11. Conference on Complex Geometry and Mirror Symmetry

    CERN Document Server

    Vinet, Luc; Yau, Shing-Tung; Mirror Symmetry III

    1999-01-01

    This book presents surveys from a workshop held during the theme year in geometry and topology at the Centre de recherches mathématiques (CRM, University of Montréal). The volume is in some sense a sequel to Mirror Symmetry I (1998) and Mirror Symmetry II (1996), copublished by the AMS and International Press. Included are recent developments in the theory of mirror manifolds and the related areas of complex and symplectic geometry. The long introductory articles explain the key physical ideas and motivation, namely conformal field theory, supersymmetry, and string theory. Open problems are emphasized. Thus the book provides an efficient way for a very broad audience of mathematicians and physicists to reach the frontier of research in this fast expanding area. - See more at: http://bookstore.ams.org/amsip-10#sthash.DbxEFJDx.dpuf

  12. Conformal Symmetry and Cosmological Entropy Production

    Directory of Open Access Journals (Sweden)

    Alexander B. Balakin

    2002-03-01

    Full Text Available Abstract: Introducing an effective refraction index of an isotropic cosmic medium, we investigate the cosmological fluid dynamics which is consistent with a conformal, timelike symmetry of a corresponding "optical" metric. We demonstrate that this kind of symmetry is compatible with the existence of a negative viscous pressure and, consequently, with cosmological entropy production. We establish an exactly solvable model according to which the viscous pressure is a consequence of a self-interacting one-particle force which is self-consistently exerted on the microscopic particles of a relativistic gas. Furthermore, we show that a suficiently high decay rate of the refraction index of an ultrarelativistic cosmic medium results in an in ationary expansion of the universe.

  13. Tensegrity structures form, stability, and symmetry

    CERN Document Server

    Zhang, Jing Yao

    2015-01-01

    To facilitate a deeper understanding of tensegrity structures, this book focuses on their two key design problems: self-equilibrium analysis and stability investigation. In particular, high symmetry properties of the structures are extensively utilized. Conditions for self-equilibrium as well as super-stability of tensegrity structures are presented in detail. An analytical method and an efficient numerical method are given for self-equilibrium analysis of tensegrity structures: the analytical method deals with symmetric structures and the numerical method guarantees super-stability. Utilizing group representation theory, the text further provides analytical super-stability conditions for the structures that are of dihedral as well as tetrahedral symmetry. This book not only serves as a reference for engineers and scientists but is also a useful source for upper-level undergraduate and graduate students. Keeping this objective in mind, the presentation of the book is self-contained and detailed, with an abund...

  14. Canonical equations of Hamilton with beautiful symmetry

    CERN Document Server

    Liang, Guo

    2012-01-01

    The Hamiltonian formulation plays the essential role in constructing the framework of modern physics. In this paper, a new form of canonical equations of Hamilton with the complete symmetry is obtained, which are valid not only for the first-order differential system, but also for the second-order differential system. The conventional form of the canonical equations without the symmetry [Goldstein et al., Classical Mechanics, 3rd ed, Addison-Wesley, 2001] are only for the second-order differential system. It is pointed out for the first time that the number of the canonical equations for the first-order differential system is half of that for the second-order differential system. The nonlinear Schr\\"{o}dinger equation, a universal first-order differential system, can be expressed with the new canonical equations in a consistent way.

  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. Duality and symmetry in chiral Potts model

    Science.gov (United States)

    Roan, Shi-shyr

    2009-08-01

    We discover an Ising-type duality in the general N-state chiral Potts model, which is the Kramers-Wannier duality of a planar Ising model when N = 2. This duality relates the spectrum and eigenvectors of one chiral Potts model at a low temperature (of small k') to those of another chiral Potts model at a high temperature (of k'-1). The τ(2) model and chiral Potts model on the dual lattice are established alongside of the dual chiral Potts models. With the aid of this duality relation, we exact a precise relationship between the Onsager-algebra symmetry of a homogeneous superintegrable chiral Potts model and the sl2-loop-algebra symmetry of its associated spin- (N-1)/2 XXZ chain through the identification of their eigenstates.

  17. SPT 2004: Symmetry and Perturbation Theory

    CERN Document Server

    Prinari, Barbara; Rauch-Wojciechowski, Stefan; Terracini, Susanna

    2005-01-01

    This proceedings volume is a collection of papers presented at the International Conference on SPT2004 focusing on symmetry, perturbation theory, and integrability. The book provides an updated overview of the recent developments in the various different fields of nonlinear dynamics, covering both theory and applications. Special emphasis is given to algebraic and geometric integrability, solutions to the N-body problem of the “choreography” type, geometry and symmetry of dynamical systems, integrable evolution equations, various different perturbation theories, and bifurcation analysis. The contributors to this volume include some of the leading scientists in the field, among them: I Anderson, D Bambusi, S Benenti, S Bolotin, M Fels, W Y Hsiang, V Matveev, A V Mikhailov, P J Olver, G Pucacco, G Sartori, M A Teixeira, S Terracini, F Verhulst and I Yehorchenko.

  18. Noether symmetries in f(G) gravity

    Energy Technology Data Exchange (ETDEWEB)

    Sharif, M., E-mail: msharif.math@pu.edu.pk; Ismat Fatima, H., E-mail: ismatfatima4@gmail.com [University of the Punjab, Deportment of Mathematics (Pakistan)

    2016-01-15

    We explore Noether symmetries of the Friedmann–Robertson–Walker universe model in modified Gauss–Bonnet gravity for both vacuum and nonvacuum (dust fluid) cases. We evaluate symmetry generators and the corresponding conserved quantities by using separation of variables and a power-law form. We construct exact f(G) models and study accelerating expansion of the universe in terms of a scale factor, deceleration, and the EoS parameters. We also check the validity of energy conditions through the weak energy conditions for our constructed model. The state finder parameters indicate the resemblance of our constructed models to the ΛCDM model. We conclude that our results are consistent with the recent astrophysical observations.

  19. Mirror symmetry for two parameter models, 2

    CERN Document Server

    Candelas, Philip; Katz, S; Morrison, Douglas Robert Ogston; Philip Candelas; Anamaria Font; Sheldon Katz; David R Morrison

    1994-01-01

    We describe in detail the space of the two K\\"ahler parameters of the Calabi--Yau manifold \\P_4^{(1,1,1,6,9)}[18] by exploiting mirror symmetry. The large complex structure limit of the mirror, which corresponds to the classical large radius limit, is found by studying the monodromy of the periods about the discriminant locus, the boundary of the moduli space corresponding to singular Calabi--Yau manifolds. A symplectic basis of periods is found and the action of the Sp(6,\\Z) generators of the modular group is determined. From the mirror map we compute the instanton expansion of the Yukawa couplings and the generalized N=2 index, arriving at the numbers of instantons of genus zero and genus one of each degree. We also investigate an SL(2,\\Z) symmetry that acts on a boundary of the moduli space.

  20. Frictional Sliding without Geometrical Reflection Symmetry

    Directory of Open Access Journals (Sweden)

    Michael Aldam

    2016-10-01

    Full Text Available The dynamics of frictional interfaces plays an important role in many physical systems spanning a broad range of scales. It is well known that frictional interfaces separating two dissimilar materials couple interfacial slip and normal stress variations, a coupling that has major implications on their stability, failure mechanism, and rupture directionality. In contrast, it is traditionally assumed that interfaces separating identical materials do not feature such a coupling because of symmetry considerations. We show, combining theory and experiments, that interfaces that separate bodies made of macroscopically identical materials but lack geometrical reflection symmetry generically feature such a coupling. We discuss two applications of this novel feature. First, we show that it accounts for a distinct, and previously unexplained, experimentally observed weakening effect in frictional cracks. Second, we demonstrate that it can destabilize frictional sliding, which is otherwise stable. The emerging framework is expected to find applications in a broad range of systems.

  1. 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

  2. Broken Symmetries and the Higgs Boson

    Directory of Open Access Journals (Sweden)

    Horváth Dezső

    2014-01-01

    Full Text Available The 40 years old Standard Model, the theory of particle physics, seems to describe all experimental data very well. The theory is based on symmetries, some of them are broken, mostly by the weak interaction. All of its elementary particles were identified and studied apart from the Higgs boson until 2012, when the two main experiments of the Large Hadron Collider at CERN, CMS and ATLAS observed a new particle with properties close to those predicted for the Higgs boson. The discovery of the Higgs boson proves the validity of the Brout-Englert-Higgs mechanism of spontaneous symmetry breaking and François Englert and Peter Higgs received the 2013 Nobel Prize in Physics. There are several questions yet concerning the possible theoretical significance of the mass of the new particle.

  3. Yangian symmetry for fishnet Feynman graphs

    Science.gov (United States)

    Chicherin, Dmitry; Kazakov, Vladimir; Loebbert, Florian; Müller, Dennis; Zhong, De-liang

    2017-12-01

    Various classes of fishnet Feynman graphs are shown to feature a Yangian symmetry over the conformal algebra. We explicitly discuss scalar graphs in three, four and six spacetime dimensions as well as the inclusion of fermions in four dimensions. The Yangian symmetry results in novel differential equations for these families of largely unsolved Feynman integrals. Notably, the considered fishnet graphs in three and four dimensions dominate the correlation functions and scattering amplitudes in specific double-scaling limits of planar, γ -twisted N =4 super Yang-Mills or Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. Consequently, the study of fishnet graphs allows us to get deep insights into the integrability of the planar AdS /CFT correspondence.

  4. Extending exchange symmetry beyond bosons and fermions

    Science.gov (United States)

    Tichy, Malte C.; Mølmer, Klaus

    2017-08-01

    We study quantum many-body states of particles subject to a more general exchange symmetry than the behavior under pairwise exchange obeyed by bosons and fermions. We refer to these hypothetical particles as immanons because the scalar product of states with the generalized exchange symmetry is the immanant of the matrix containing all mutual scalar products of the occupied single-particle states, a generalization of the determinant and permanent applied for fermions and bosons. Immanons are shown to obey a partial Pauli principle that forbids the occupation of single-particle states above certain threshold numbers. This has measurable consequences for their tendency to favor or oppose multiple occupation of single-particle modes, and it links conjectured mathematical properties of immanants to the expected outcome of a physical Gedanken experiment.

  5. Symmetry Breaking in a random passive scalar

    Science.gov (United States)

    Kilic, Zeliha; McLaughlin, Richard; Camassa, Roberto

    2017-11-01

    We consider the evolution of a decaying passive scalar in the presence of a gaussian white noise fluctuating shear flow. We focus on deterministic initial data and establish the short, intermediate, and long time symmetry properties of the evolving point wise probability measure for the random passive scalar. Analytical results are compared directly to Monte Carlo simulations. Time permitting we will compare the predictions to experimental observations.

  6. Symmetry in monotone Lagrangian Floer theory

    OpenAIRE

    Smith, Jack Edward

    2017-01-01

    In this thesis we study the self-Floer theory of a monotone Lagrangian submanifold $L$ of a closed symplectic manifold $X$ in the presence of various kinds of symmetry. First we consider the group $\\mathrm{Symp}(X, L)$ of symplectomorphisms of $X$ preserving $L$ setwise, and extend its action on the Oh spectral sequence to coefficients of arbitrary characteristic, working over an enriched Novikov ring. This imposes constraints on the differentials in the spectral sequence which force them to...

  7. Quantum nuclear pasta and nuclear symmetry energy

    Science.gov (United States)

    Fattoyev, F. J.; Horowitz, C. J.; Schuetrumpf, B.

    2017-05-01

    Complex and exotic nuclear geometries, collectively referred to as "nuclear pasta," are expected to appear naturally in dense nuclear matter found in the crusts of neutron stars and supernovae environments. The pasta geometries depend on the average baryon density, proton fraction, and temperature and are critically important in the determination of many transport properties of matter in supernovae and the crusts of neutron stars. Using a set of self-consistent microscopic nuclear energy density functionals, we present the first results of large scale quantum simulations of pasta phases at baryon densities 0.03 ≤ρ ≤0.10 fm-3 , proton fractions 0.05 ≤Yp≤0.40 , and zero temperature. The full quantum simulations, in particular, allow us to thoroughly investigate the role and impact of the nuclear symmetry energy on pasta configurations. We use the Sky3D code that solves the Skyrme Hartree-Fock equations on a three-dimensional Cartesian grid. For the nuclear interaction we use the state-of-the-art UNEDF1 parametrization, which was introduced to study largely deformed nuclei, hence is suitable for studies of the nuclear pasta. Density dependence of the nuclear symmetry energy is simulated by tuning two purely isovector observables that are insensitive to the current available experimental data. We find that a minimum total number of nucleons A =2000 is necessary to prevent the results from containing spurious shell effects and to minimize finite size effects. We find that a variety of nuclear pasta geometries are present in the neutron star crust, and the result strongly depends on the nuclear symmetry energy. The impact of the nuclear symmetry energy is less pronounced as the proton fractions increase. Quantum nuclear pasta calculations at T =0 MeV are shown to get easily trapped in metastable states, and possible remedies to avoid metastable solutions are discussed.

  8. Efficient detection of symmetries polynomially parametrized curves

    OpenAIRE

    Alcázar Arribas, Juan Gerardo

    2014-01-01

    We present efficient algorithms for detecting central and mirror symmetry for the case of algebraic curves defined by means of polynomial parametrizations. The algorithms are based on an algebraic relationship between proper parametrizations of a same curve, which leads to a triangular polynomial system that can be solved in a very fast way; in particular, curves parametrized by polynomials of serious degrees/coefficients can be analyzed in a few seconds. In our analysis we provide a good num...

  9. Human body odour, symmetry and attractiveness.

    OpenAIRE

    Rikowski, A; Grammer, K

    1999-01-01

    Several studies have found body and facial symmetry as well as attractiveness to be human mate choice criteria. These characteristics are presumed to signal developmental stability. Human body odour has been shown to influence female mate choice depending on the immune system, but the question of whether smell could signal general mate quality, as do other cues, was not addressed in previous studies. We compared ratings of body odour, attractiveness, and measurements of facial and body asymme...

  10. Cluster dynamics and symmetries in light nuclei

    Directory of Open Access Journals (Sweden)

    Freer Martin

    2016-01-01

    Full Text Available Many light nuclei display behaviour that indicates that, rather than behaving as an A-body system of individual nucleons, the degrees of freedom are those of clusters. The appearance of α-particle clustering is most widespread. In the present proceedings the symmetries and dynamics of the nuclei 8Be, 12C and 16O are examined together with some recent experimental measurements.

  11. Symmetry: a bridge between nature and culture

    CERN Document Server

    Mouchet, Amaury

    2015-01-01

    Are symmetries discovered or rather invented by humans ? The stand you may take firmly here reveals a lot of your epistemological position. Conversely, the arguments you may forge for answering to this question, or to one of its numerous narrower or broader variations, shape your whole philosophical thoughts; not specifically about science, by the way. I will try to show how physics helps to (re)consider this issue.

  12. Pole Inflation - Shift Symmetry and Universal Corrections

    OpenAIRE

    Broy, Benedict J.; Galante, Mario; Roest, Diederik; Westphal, Alexander

    2015-01-01

    An appealing explanation for the Planck data is provided by inflationary mod els with a singular non-canonical kinetic term: a Laurent expansion of the kinetic function translates into a potential with a nearly shift-symmetric plateau in canonical fields. The shift symmetry can be broken at large field values by including higher-order poles, which need to be hierarchically suppressed in order not to spoil the inflationary plateau. The herefrom resulting corrections to the inflationary dynamic...

  13. Black holes, hidden symmetries, and complete integrability

    Science.gov (United States)

    Frolov, Valeri P.; Krtouš, Pavel; Kubizňák, David

    2017-11-01

    The study of higher-dimensional black holes is a subject which has recently attracted vast interest. Perhaps one of the most surprising discoveries is a realization that the properties of higher-dimensional black holes with the spherical horizon topology and described by the Kerr-NUT-(A)dS metrics are very similar to the properties of the well known four-dimensional Kerr metric. This remarkable result stems from the existence of a single object called the principal tensor. In our review we discuss explicit and hidden symmetries of higher-dimensional Kerr-NUT-(A)dS black hole spacetimes. We start with discussion of the Killing and Killing-Yano objects representing explicit and hidden symmetries. We demonstrate that the principal tensor can be used as a "seed object" which generates all these symmetries. It determines the form of the geometry, as well as guarantees its remarkable properties, such as special algebraic type of the spacetime, complete integrability of geodesic motion, and separability of the Hamilton-Jacobi, Klein-Gordon, and Dirac equations. The review also contains a discussion of different applications of the developed formalism and its possible generalizations.

  14. Financial symmetry and moods in the market.

    Directory of Open Access Journals (Sweden)

    Roberto Savona

    Full Text Available This paper studies how certain speculative transitions in financial markets can be ascribed to a symmetry break that happens in the collective decision making. Investors are assumed to be bounded rational, using a limited set of information including past price history and expectation on future dividends. Investment strategies are dynamically changed based on realized returns within a game theoretical scheme with Nash equilibria. In such a setting, markets behave as complex systems whose payoff reflect an intrinsic financial symmetry that guarantees equilibrium in price dynamics (fundamentalist state until the symmetry is broken leading to bubble or anti-bubble scenarios (speculative state. We model such two-phase transition in a micro-to-macro scheme through a Ginzburg-Landau-based power expansion leading to a market temperature parameter which modulates the state transitions in the market. Via simulations we prove that transitions in the market price dynamics can be phenomenologically explained by the number of traders, the number of strategies and amount of information used by agents, all included in our market temperature parameter.

  15. Financial symmetry and moods in the market.

    Science.gov (United States)

    Savona, Roberto; Soumare, Maxence; Andersen, Jørgen Vitting

    2015-01-01

    This paper studies how certain speculative transitions in financial markets can be ascribed to a symmetry break that happens in the collective decision making. Investors are assumed to be bounded rational, using a limited set of information including past price history and expectation on future dividends. Investment strategies are dynamically changed based on realized returns within a game theoretical scheme with Nash equilibria. In such a setting, markets behave as complex systems whose payoff reflect an intrinsic financial symmetry that guarantees equilibrium in price dynamics (fundamentalist state) until the symmetry is broken leading to bubble or anti-bubble scenarios (speculative state). We model such two-phase transition in a micro-to-macro scheme through a Ginzburg-Landau-based power expansion leading to a market temperature parameter which modulates the state transitions in the market. Via simulations we prove that transitions in the market price dynamics can be phenomenologically explained by the number of traders, the number of strategies and amount of information used by agents, all included in our market temperature parameter.

  16. Inequivalence of coset constructions for spacetime symmetries

    Energy Technology Data Exchange (ETDEWEB)

    Creminelli, Paolo [Abdus Salam International Centre for Theoretical Physics,Strada Costiera 11, 34151 Trieste (Italy); Institute for Advanced Study, Princeton, NJ 08540 (United States); Serone, Marco [SISSA, via Bonomea 265, 34136 Trieste (Italy); Abdus Salam International Centre for Theoretical Physics,Strada Costiera 11, 34151 Trieste (Italy); INFN - Sezione di Trieste, 34151 Trieste (Italy); Trevisan, Gabriele [SISSA, via Bonomea 265, 34136 Trieste (Italy); INFN - Sezione di Trieste, 34151 Trieste (Italy); Trincherini, Enrico [Scuola Normale Superiore, piazza dei Cavalieri 7, 56126 Pisa (Italy); INFN - Sezione di Pisa, 56100 Pisa (Italy)

    2015-02-05

    Non-linear realizations of spacetime symmetries can be obtained by a generalization of the coset construction valid for internal ones. The physical equivalence of different representations for spacetime symmetries is not obvious, since their relation involves not only a redefinition of the fields but also a field-dependent change of coordinates. A simple and relevant spacetime symmetry is obtained by the contraction of the 4D conformal group that leads to the Galileon group. We analyze two non-linear realizations of this group, focusing in particular on the propagation of signals around non-trivial backgrounds. The aperture of the lightcone is in general different in the two representations and in particular a free (luminal) massless scalar is mapped in a Galileon theory which admits superluminal propagation. We show that in this theory, if we consider backgrounds that vanish at infinity, there is no asymptotic effect: the displacement of the trajectory integrates to zero, as can be expected since the S-matrix is trivial. Regarding local measurements, we show that the puzzle is solved taking into account that a local coupling with fixed sources in one theory is mapped into a non-local coupling and we show that this effect compensates the different lightcone. Therefore the two theories have a different notion of locality. The same applies to the different non-linear realizations of the conformal group and we study the particular case of a cosmologically interesting background: the Galilean Genesis scenarios.

  17. Generalized global symmetries and dissipative magnetohydrodynamics

    Science.gov (United States)

    Grozdanov, Sašo; Hofman, Diego M.; Iqbal, Nabil

    2017-05-01

    The conserved magnetic flux of U (1 ) electrodynamics coupled to matter in four dimensions is associated with a generalized global symmetry. We study the realization of such a symmetry at finite temperature and develop the hydrodynamic theory describing fluctuations of a conserved 2-form current around thermal equilibrium. This can be thought of as a systematic derivation of relativistic magnetohydrodynamics, constrained only by symmetries and effective field theory. We construct the entropy current and show that at first order in derivatives, there are seven dissipative transport coefficients. We present a universal definition of resistivity in a theory of dynamical electromagnetism and derive a direct Kubo formula for the resistivity in terms of correlation functions of the electric field operator. We also study fluctuations and collective modes, deriving novel expressions for the dissipative widths of magnetosonic and Alfvén modes. Finally, we demonstrate that a nontrivial truncation of the theory can be performed at low temperatures compared to the magnetic field: this theory has an emergent Lorentz invariance along magnetic field lines, and hydrodynamic fluctuations are now parametrized by a fluid tensor rather than a fluid velocity. Throughout, no assumption is made of weak electromagnetic coupling. Thus, our theory may have phenomenological relevance for dense electromagnetic plasmas.

  18. Black holes, hidden symmetries, and complete integrability.

    Science.gov (United States)

    Frolov, Valeri P; Krtouš, Pavel; Kubizňák, David

    2017-01-01

    The study of higher-dimensional black holes is a subject which has recently attracted vast interest. Perhaps one of the most surprising discoveries is a realization that the properties of higher-dimensional black holes with the spherical horizon topology and described by the Kerr-NUT-(A)dS metrics are very similar to the properties of the well known four-dimensional Kerr metric. This remarkable result stems from the existence of a single object called the principal tensor. In our review we discuss explicit and hidden symmetries of higher-dimensional Kerr-NUT-(A)dS black hole spacetimes. We start with discussion of the Killing and Killing-Yano objects representing explicit and hidden symmetries. We demonstrate that the principal tensor can be used as a "seed object" which generates all these symmetries. It determines the form of the geometry, as well as guarantees its remarkable properties, such as special algebraic type of the spacetime, complete integrability of geodesic motion, and separability of the Hamilton-Jacobi, Klein-Gordon, and Dirac equations. The review also contains a discussion of different applications of the developed formalism and its possible generalizations.

  19. A Conjectured Bound on Accidental Symmetries

    CERN Document Server

    Buican, Matthew

    2012-01-01

    In this note, we study a large class of four-dimensional R-symmetric theories, and we describe a new quantity, \\tau_U, which is well-defined in these theories. Furthermore, we conjecture that this quantity is larger in the ultraviolet (UV) than in the infrared (IR), i.e. that \\tau_U^{UV}>\\tau_U^{IR}. While we do not prove this inequality in full generality, it is straightforward to show that our conjecture holds in the subset of theories that do not have accidental symmetries. In addition, we subject our inequality to an array of non-trivial tests in theories with accidental symmetries and dramatically different dynamics both in N=1 and N=2 supersymmetry and find that our inequality is obeyed. One interesting consequence of this conjecture is that the mixing of accidental symmetries with the IR superconformal R current is bounded by the UV quantity, \\tau_U^{UV}. To demonstrate the potential utility of this bound, we apply it to the somewhat mysterious SU(2) gauge theory of Intriligator, Seiberg, and Shenker a...

  20. Chiral symmetry breaking in unstirred crystallization

    Energy Technology Data Exchange (ETDEWEB)

    Szurgot, M. [Center of Mathematics and Physics, Technical University of Lodz (Poland)

    2012-01-15

    Statistics of nucleation of chiral forms of sodium bromate from unstirred aqueous solutions was studied. It was established that bimodal, trimodal and unimodal distributions of enantiomers are obtained in unstirred crystallization. It was also found out that probabilities of the creation of L or D crystals and racemates R, as well as the presence of D, L, and R peaks in distributions depend on crystallizer size, supersaturation and temperature. Nucleation at low supersaturations in small, closed crystallizers leads to the formation of pure enantiomers, and to bimodal distributions with D and L peaks at any temperature. At high supersaturations in large, open crystallizers the formation of racemates and unimodal distributions with racemate R peaks results. In open crystallizers at the lowest temperatures and at the highest temperatures used in crystallization from aqueous solution racemates of sodium bromate are preferentially formed, but in a wide range of intermediate-temperatures apart from racemates, pure enantiomers are efficiently formed which leads to trimodal distributions. The spontaneous formation of pure enantiomers in crystallization from unstirred, unseeded solutions is caused by the chiral symmetry breaking phenomenon, the same as that discovered in stirred crystallization. The conservation of chiral symmetry is, in unstirred crystallization, one of the two possibilities, and the other one is the breakage of symmetry. Both of them occur in nature. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  1. Constraining the physical state by symmetries

    Energy Technology Data Exchange (ETDEWEB)

    Fatibene, L., E-mail: lorenzo.fatibene@unito.it [Department of Mathematics, University of Torino (Italy); INFN - Sezione Torino - IS QGSKY (Italy); Ferraris, M.; Magnano, G. [Department of Mathematics, University of Torino (Italy)

    2017-03-15

    After reviewing the hole argument and its relations with initial value problem and general covariance, we shall discuss how much freedom one has to define the physical state in a generally covariant field theory (with or without internal gauge symmetries). Our analysis relies on Cauchy problems, thus it is restricted to globally hyperbolic spacetimes. We shall show that in generally covariant theories on a compact space (as well as for internal gauge symmetries on any spacetime) one has no freedom and one is forced to declare as physically equivalent two configurations which differ by a global spacetime diffeomorphism (or by an internal gauge transformation) as it is usually prescribed. On the contrary, when space is not compact, the result does not hold true and one may have different options to define physically equivalent configurations, still preserving determinism. - Highlights: • Investigate the relation between the hole argument, covariance, determinism and physical state. • Show that if space is compact then any diffeomorphism is a gauge symmetry. • Show that if space is not compact then there may be more freedom in choosing gauge group.

  2. Financial Symmetry and Moods in the Market

    Science.gov (United States)

    Savona, Roberto; Soumare, Maxence; Andersen, Jørgen Vitting

    2015-01-01

    This paper studies how certain speculative transitions in financial markets can be ascribed to a symmetry break that happens in the collective decision making. Investors are assumed to be bounded rational, using a limited set of information including past price history and expectation on future dividends. Investment strategies are dynamically changed based on realized returns within a game theoretical scheme with Nash equilibria. In such a setting, markets behave as complex systems whose payoff reflect an intrinsic financial symmetry that guarantees equilibrium in price dynamics (fundamentalist state) until the symmetry is broken leading to bubble or anti-bubble scenarios (speculative state). We model such two-phase transition in a micro-to-macro scheme through a Ginzburg-Landau-based power expansion leading to a market temperature parameter which modulates the state transitions in the market. Via simulations we prove that transitions in the market price dynamics can be phenomenologically explained by the number of traders, the number of strategies and amount of information used by agents, all included in our market temperature parameter. PMID:25856392

  3. A nonlinear extension of the spin-2 partially massless symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Saenz, Sebastian; Rosen, Rachel A. [Physics Department and Institute for Strings, Cosmology, and Astroparticle Physics, Columbia University, New York, NY 10027 (United States)

    2015-05-07

    We investigate the possibility of extending the “partially massless” symmetry of a spin-2 field in de Sitter to nonlinear order. To do so, we impose a closure condition on the symmetry transformations. This requirement imposes strong constraints on the form of the nonlinear symmetry while making only minimal assumptions about the form of the nonlinear partially massless action. We find a unique nonlinear extension of the free partially massless symmetry. However, we show that no consistent Lagrangian that contains at most two derivatives of the fields can realize this symmetry.

  4. Applications of Symmetry Methods to the Theory of Plasma Physics

    Directory of Open Access Journals (Sweden)

    Giampaolo Cicogna

    2006-02-01

    Full Text Available The theory of plasma physics offers a number of nontrivial examples of partial differential equations, which can be successfully treated with symmetry methods. We propose three different examples which may illustrate the reciprocal advantage of this "interaction" between plasma physics and symmetry techniques. The examples include, in particular, the complete symmetry analysis of system of two PDE's, with the determination of some conditional and partial symmetries, the construction of group-invariant solutions, and the symmetry classification of a nonlinear PDE.

  5. Bridge the Gap.

    Science.gov (United States)

    Klein, Mel; Cufaude, Jeffrey B.

    1989-01-01

    This document consists of two paired articles: the first, "Preparing Faculty Out of Class Experiences," by Mel Klein, and the second, "Help Advisers Be More Than Ghost Signatures," by Jeffrey B. Calfaude. Each article shares insights on how faculty advisers "bridge the gap" between students and faculty. When faculty members are asked to advise…

  6. Bridging the gap

    Science.gov (United States)

    2012-08-01

    Astronomy is flourishing in China, with impressive achievements in instrument design and construction matched by a higher international research profile. Yet there remains a mismatch between the facilities available and those needed to progress. Sue Bowler wonders how the country will bridge the gap.

  7. Semantic Gaps Are Dangerous

    DEFF Research Database (Denmark)

    Ejstrup, Michael; le Fevre Jakobsen, Bjarne

    2014-01-01

    Semantic gaps are dangerous Language adapts to the environment where it serves as a tool to communication. Language is a social agreement, and we all have to stick to both grammaticalized and non-grammaticalized rules in order to pass information about the world around us. As such language develops...

  8. Bridging the Emissions Gap

    NARCIS (Netherlands)

    Blok, K.

    2012-01-01

    The analyses in Chapters 2 and 3 of this report concluded that the emissions gap in 2020 will likely be between 8 and 13 GtCO2e. The chapters also estimated the difference between BaU emissions in 2020 and the emissions level consistent with a “likely” chance of staying within the 2°C target to

  9. Estimating Gender Wage Gaps

    Science.gov (United States)

    McDonald, Judith A.; Thornton, Robert J.

    2011-01-01

    Course research projects that use easy-to-access real-world data and that generate findings with which undergraduate students can readily identify are hard to find. The authors describe a project that requires students to estimate the current female-male earnings gap for new college graduates. The project also enables students to see to what…

  10. Interocular symmetry analysis of bilateral eyes.

    Science.gov (United States)

    Li, Yi; Bao, Fang Jun

    2014-05-01

    The purpose of this study was to evaluate the interocular symmetry of several biometric parameters between both eyes. The symmetry between the right and left eye of 397 subjects in 14 biometric parameters, spherical equivalent of refractive error (SE), Jackson crossed cylinder power of refractive error astigmatism with axes at 90° and 180° (RJ0) and at 45° and 135° (RJ45), best-corrected visual acuity (BCVA), average corneal curvature (CC), Jackson crossed cylinder power of corneal astigmatism (CJ0 and CJ45), corneal asphericity coefficient (Q), intraocular pressure (IOP), central corneal thickness (CCT), axial length (AL), anterior chamber depth (ACD), lens thickness (LT) and vitreous chamber depth (VCD), was assessed by comparative data analysis. Aside from RJ0 (p = 0.00), RJ45 (p = 0.02) and Q (p = 0.00), the overall interocular differences of other biometric parameters between fellow eyes were not significant (p > 0.05). The interocular correlation and Bland-Altman plots showed a good agreement between fellow eyes in 14 biometric parameters. Correlations between interocular differences in SE and that in RJ0 (p = 0.03), CC (p = 0.00), AL (p = 0.00) and VCD (p = 0.00) were statistically significant. There were similar strong linear relationships between refractive error astigmatism vectors and corneal astigmatism vectors in bilateral eyes. There were negative correlations of RJ45 and CJ45 between bilateral eyes. A potentially clinically important interocular symmetry in SE, BCVA, CC, CJ0, CJ45, IOP, CCT, AL, ACD, LT and VCD is found in this research, while the differences of RJ0, RJ45 and Q between left and right eyes seem a bit large. The negative interocular relationships of RJ45 and CJ45 demonstrate moderate mirror symmetry exists among fellow eyes. High interocular symmetry in bilateral eyes may be helpful in intraocular lens power calculation, intraocular pressure evaluation, post-operative visual acuity and refraction

  11. Symmetry-induced quantum interference effects in metalloporphyrin wires.

    Science.gov (United States)

    Ferradás, R; García-Suárez, V M; Ferrer, J

    2013-08-14

    We calculate the electronic and transport properties of a series of metalloporphyrin molecules sandwiched between gold electrodes using a combination of density functional theory and scattering theory. The impact of strong correlations at the central metallic atom is gauged by comparing our results obtained using conventional DFT and DFT + U approaches. The zero- and finite-bias transport properties may or may not show spin-filtering behavior, depending on the nature of the d state closest to the Fermi energy. The type of d state depends on the metallic atom and gives rise to interference effects that produce different Fano features. The inclusion of the U term opens a gap between the d states and changes the conductance and spin-filtering behavior qualitatively in some of the molecules. We explain the origin of the quantum interference effects found as due to the symmetry-dependent coupling between the d states and other molecular orbitals and propose the use of these systems as nanoscale chemical sensors. We also demonstrate that an adequate treatment of strong correlations is really necessary to correctly describe the transport properties of metalloporphyrins and similar molecular magnets.

  12. Deciphering the 3-D distribution of fluid along the shallow Hikurangi subduction zone using P- and S-wave attenuation

    Science.gov (United States)

    Eberhart-Phillips, Donna; Bannister, Stephen; Reyners, Martin

    2017-11-01

    We use local earthquake velocity spectra to solve for the 3-D distribution of P- and S-wave attenuation in the shallow Hikurangi subduction zone in the North Island of New Zealand to gain insight into how fluids control both the distribution of slip rate deficit and slow-slip events at the shallow plate interface. Qs/Qp gives us information on the 3-D distribution of fluid saturation, which we can compare with the previously determined 3-D distribution of Vp/Vs, which gives information on pore fluid pressure. The Hikurangi margin is unusual, in that a large igneous province (the Hikurangi Plateau) is being subducted. This plateau has had two episodes of subduction—first at 105-100 Ma during north-south convergence with Gondwana, and currently during east-west convergence between the Pacific and Australian plates. We find that in the southern part of the subduction zone, where there is a large deficit in slip rate at the plate interface, the plate interface region is only moderately fluid-rich because the underlying plateau had already had an episode of dehydration during Gondwana subduction. But fluid pressure is relatively high, due to an impermeable terrane in the upper plate trapping fluids below the plate interface. The central part of the margin, where the slip rate deficit is very low, is the most fluid-rich part of the shallow subduction zone. We attribute this to an excess of fluid from the subducted plateau. Our results suggest this part of the plateau has unusually high fracture permeability, on account of it having had two episodes of bending—first at the Gondwana trench and now at the Hikurangi Trough. Qs/Qp is consistent with fluids migrating across the plate interface in this region, leaving it drained and producing high fluid pressure in the overlying plate. The northern part of the margin is a region of heterogeneous deficit in slip rate. Here the Hikurangi Plateau is subducting for the first time, so there is less fluid available from its

  13. Trinucleotide's quadruplet symmetries and natural symmetry law of DNA creation ensuing Chargaff's second parity rule.

    Science.gov (United States)

    Rosandić, Marija; Vlahović, Ines; Glunčić, Matko; Paar, Vladimir

    2016-07-01

    For almost 50 years the conclusive explanation of Chargaff's second parity rule (CSPR), the equality of frequencies of nucleotides A=T and C=G or the equality of direct and reverse complement trinucleotides in the same DNA strand, has not been determined yet. Here, we relate CSPR to the interstrand mirror symmetry in 20 symbolic quadruplets of trinucleotides (direct, reverse complement, complement, and reverse) mapped to double-stranded genome. The symmetries of Q-box corresponding to quadruplets can be obtained as a consequence of Watson-Crick base pairing and CSPR together. Alternatively, assuming Natural symmetry law for DNA creation that each trinucleotide in one strand of DNA must simultaneously appear also in the opposite strand automatically leads to Q-box direct-reverse mirror symmetry which in conjunction with Watson-Crick base pairing generates CSPR. We demonstrate quadruplet's symmetries in chromosomes of wide range of organisms, from Escherichia coli to Neanderthal and human genomes, introducing novel quadruplet-frequency histograms and 3D-diagrams with combined interstrand frequencies. These "landscapes" are mutually similar in all mammals, including extinct Neanderthals, and somewhat different in most of older species. In human chromosomes 1-12, and X, Y the "landscapes" are almost identical and slightly different in the remaining smaller and telocentric chromosomes. Quadruplet frequencies could provide a new robust tool for characterization and classification of genomes and their evolutionary trajectories.

  14. Symbolic Detection of Permutation and Parity Symmetries of Evolution Equations

    KAUST Repository

    Alghamdi, Moataz

    2017-06-18

    We introduce a symbolic computational approach to detecting all permutation and parity symmetries in any general evolution equation, and to generating associated invariant polynomials, from given monomials, under the action of these symmetries. Traditionally, discrete point symmetries of differential equations are systemically found by solving complicated nonlinear systems of partial differential equations; in the presence of Lie symmetries, the process can be simplified further. Here, we show how to find parity- and permutation-type discrete symmetries purely based on algebraic calculations. Furthermore, we show that such symmetries always form groups, thereby allowing for the generation of new group-invariant conserved quantities from known conserved quantities. This work also contains an implementation of the said results in Mathematica. In addition, it includes, as a motivation for this work, an investigation of the connection between variational symmetries, described by local Lie groups, and conserved quantities in Hamiltonian systems.

  15. Quantum mechanics. Symmetries. 5. corr. ed.; Quantenmechanik. Symmetrien

    Energy Technology Data Exchange (ETDEWEB)

    Greiner, Walter [Frankfurt Univ. (Germany). Frankfurt Inst. for Advanced Studies; Mueller, Berndt [Duke Univ., Durham, NC (United States). Dept. of Physics

    2014-07-01

    The volume quantum mechanics treats the as elegant as mighty theory of the symmetry groups and their application in quantum mechanics and the theory of the elementary particles. By means of many examples and problems with worked-out solutions the application of the fundamental principles to realistic problems is elucidated. The themes are symmetries in quantum mechanics, representations of the algebra of the angular momentum operators as generators of the SO(3) group. fundamental properties of Lie groups as mathematical supplement, symmetry groups and their physical meaning, thr isospin group, the hypercharge, quarks and the symmetry group SU(3), representations of the permutation group and Young diagrams, group characters as mathematical supplement, charm and the symmetry group SU(4), Cartan-Weyl claasification as mathematical supplement, special discrete symmetries, dynamical symmetries and the hydrogen atom, non-compact Lie groups as mathematical supplement, a proof of Racah's theorem.

  16. Exactly solvable models for symmetry-enriched topological phases

    Science.gov (United States)

    Cheng, Meng; Gu, Zheng-Cheng; Jiang, Shenghan; Qi, Yang

    2017-09-01

    We construct fixed-point wave functions and exactly solvable commuting-projector Hamiltonians for a large class of bosonic symmetry-enriched topological (SET) phases, based on the concept of equivalent classes of symmetric local unitary transformations. We argue that for onsite unitary symmetries, our construction realizes all SETs free of anomaly, as long as the underlying topological order itself can be realized with a commuting-projector Hamiltonian. We further extend the construction to antiunitary symmetries (e.g., time-reversal symmetry), mirror-reflection symmetries, and to anomalous SETs on the surface of three-dimensional symmetry-protected topological phases. Mathematically, our construction naturally leads to a generalization of group extensions of unitary fusion categories to antiunitary symmetries.

  17. Convenient method for estimating underground s-wave velocity structure utilizing horizontal and vertical components microtremor spectral ratio; Bido no suiheido/jogedo supekutoru hi wo riyoshita kan`i chika s ha sokudo kozo suiteiho

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, H.; Yoshioka, M.; Saito, T. [Iwate University, Iwate (Japan). Faculty of Engineering

    1996-05-01

    Studies were conducted about the method of estimating the underground S-wave velocity structure by inversion making use of the horizontal/vertical motion spectral ratio of microtremors. For this purpose, a dynamo-electric velocity type seismograph was used, capable of processing the east-west, north-south, and vertical components integratedly. For the purpose of sampling the Rayleigh wave spectral ratio, one out of all the azimuths was chosen, whose horizontal motion had a high Fourier frequency component coherency with the vertical motions. For the estimation of the underground S-wave velocity structure, parameters (P-wave velocity, S-wave velocity, density, and layer thickness) were determined from the minimum residual sum of squares involving the observed microtremor spectral ratio and the theoretical value calculated by use of a model structure. The known boring data was utilized for the study of the S-wave velocity in the top layer, and it was determined using an S-wave velocity estimation formula for the Morioka area constructed using the N-value, depth, and geological classification. It was found that the optimum S-wave velocity structure even below the top layer well reflects the S-wave velocity obtained by the estimation formula. 5 refs., 6 figs.

  18. Is space-time symmetry a suitable generalization of parity-time symmetry?

    Energy Technology Data Exchange (ETDEWEB)

    Amore, Paolo, E-mail: paolo.amore@gmail.com [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal Díaz del Castillo 340, Colima, Colima (Mexico); Fernández, Francisco M., E-mail: fernande@quimica.unlp.edu.ar [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina); Garcia, Javier [INIFTA (UNLP, CCT La Plata-CONICET), División Química Teórica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)

    2014-11-15

    We discuss space-time symmetric Hamiltonian operators of the form H=H{sub 0}+igH{sup ′}, where H{sub 0} is Hermitian and g real. H{sub 0} is invariant under the unitary operations of a point group G while H{sup ′} is invariant under transformation by elements of a subgroup G{sup ′} of G. If G exhibits irreducible representations of dimension greater than unity, then it is possible that H has complex eigenvalues for sufficiently small nonzero values of g. In the particular case that H is parity-time symmetric then it appears to exhibit real eigenvalues for all 0symmetry and perturbation theory enable one to predict whether H may exhibit real or complex eigenvalues for g>0. We illustrate the main theoretical results and conclusions of this paper by means of two- and three-dimensional Hamiltonians exhibiting a variety of different point-group symmetries. - Highlights: • Space-time symmetry is a generalization of PT symmetry. • The eigenvalues of a space-time Hamiltonian are either real or appear as pairs of complex conjugate numbers. • In some cases all the eigenvalues are real for some values of a potential-strength parameter g. • At some value of g space-time symmetry is broken and complex eigenvalues appear. • Some multidimensional oscillators exhibit broken space-time symmetry for all values of g.

  19. 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.

  20. Variational method of determining effective moduli of polycrystals: (A) hexagonal symmetry, (B) trigonal symmetry

    Science.gov (United States)

    Peselnick, L.; Meister, R.

    1965-01-01

    Variational principles of anisotropic elasticity have been applied to aggregates of randomly oriented pure-phase polycrystals having hexagonal symmetry and trigonal symmetry. The bounds of the effective elastic moduli obtained in this way show a considerable improvement over the bounds obtained by means of the Voigt and Reuss assumptions. The Hill average is found to be in most cases a good approximation when compared to the bounds found from the variational method. The new bounds reduce in their limits to the Voigt and Reuss values. ?? 1965 The American Institute of Physics.