Phase space methods for Majorana fermions

Science.gov (United States)

Rushin Joseph, Ria; Rosales-Zárate, Laura E. C.; Drummond, Peter D.

2018-06-01

Fermionic phase space representations are a promising method for studying correlated fermion systems. The fermionic Q-function and P-function have been defined using Gaussian operators of fermion annihilation and creation operators. The resulting phase-space of covariance matrices belongs to the symmetry class D, one of the non-standard symmetry classes. This was originally proposed to study mesoscopic normal-metal-superconducting hybrid structures, which is the type of structure that has led to recent experimental observations of Majorana fermions. Under a unitary transformation, it is possible to express these Gaussian operators using real anti-symmetric matrices and Majorana operators, which are much simpler mathematical objects. We derive differential identities involving Majorana fermion operators and an antisymmetric matrix which are relevant to the derivation of the corresponding Fokker–Planck equations on symmetric space. These enable stochastic simulations either in real or imaginary time. This formalism has direct relevance to the study of fermionic systems in which there are Majorana type excitations, and is an alternative to using expansions involving conventional Fermi operators. The approach is illustrated by showing how a linear coupled Hamiltonian as used to study topological excitations can be transformed to Fokker–Planck and stochastic equation form, including dissipation through particle losses.

Dynamical FLIC fermions

International Nuclear Information System (INIS)

Kamleh, W.; Leinweber, D.B.; Williams, A.G.

2004-01-01

The use of APE smearing or other blocking techniques in fermion actions can provide many advantages. There are many variants of these fat link actions in lattice QCD currently, such as FLIC fermions. The FLIC fermion formalism makes use of the APE blocking technique in combination with a projection of the blocked links back into the special unitary group. This reunitarisation is often performed using an iterative maximisation of a gauge invariant measure. This technique is not differentiable with respect to the gauge field and thus prevents the use of standard. Hybrid Monte Carlo simulation algorithms. The use of an alternative projection technique circumvents this difficulty and allows the simulation of dynamical fat link fermions with standard HMC and its variants

Fermion number non-conservation and cold neutral fermionic matter in (V-A) gauge theories

International Nuclear Information System (INIS)

Matveev, V.A.; Rubakov, V.A.; Tavkhelidze, A.N.; Tokarev, V.F.

1987-01-01

It is shown that in four-dimensional abelian (V-A) theories, the ground state of cold neutral fermionic matter is an anomalous state containing domains of abnormal phase surrounded by the normal vacuum. Inside these domains, there exists a gauge field condensate which makes real fermions disappear both inside and outside the domains. In non-abelian theories, the abnormal matter is unstable in its turn, and the system rolls back down into the normal state with a small number of fermions above the topologically non-trivial vacuum. Thus, in several non-abelian gauge theories, the fermion number density of cold neutral matter cannot exceed some critical value. (orig.)

Noether symmetry for non-minimally coupled fermion fields

International Nuclear Information System (INIS)

Souza, Rudinei C de; Kremer, Gilberto M

2008-01-01

A cosmological model where a fermion field is non-minimally coupled with the gravitational field is studied. By applying Noether symmetry the possible functions for the potential density of the fermion field and for the coupling are determined. Cosmological solutions are found showing that the non-minimally coupled fermion field behaves as an inflaton describing an inflationary scenario, whereas the minimally coupled fermion field describes a decelerated period, behaving as a standard matter field

Fermions from classical statistics

International Nuclear Information System (INIS)

Wetterich, C.

2010-01-01

We describe fermions in terms of a classical statistical ensemble. The states τ of this ensemble are characterized by a sequence of values one or zero or a corresponding set of two-level observables. Every classical probability distribution can be associated to a quantum state for fermions. If the time evolution of the classical probabilities p τ amounts to a rotation of the wave function q τ (t)=±√(p τ (t)), we infer the unitary time evolution of a quantum system of fermions according to a Schroedinger equation. We establish how such classical statistical ensembles can be mapped to Grassmann functional integrals. Quantum field theories for fermions arise for a suitable time evolution of classical probabilities for generalized Ising models.

Non-unitary probabilistic quantum computing circuit and method

Science.gov (United States)

Williams, Colin P. (Inventor); Gingrich, Robert M. (Inventor)

2009-01-01

A quantum circuit performing quantum computation in a quantum computer. A chosen transformation of an initial n-qubit state is probabilistically obtained. The circuit comprises a unitary quantum operator obtained from a non-unitary quantum operator, operating on an n-qubit state and an ancilla state. When operation on the ancilla state provides a success condition, computation is stopped. When operation on the ancilla state provides a failure condition, computation is performed again on the ancilla state and the n-qubit state obtained in the previous computation, until a success condition is obtained.

Non-perturbative renormalisation of left-left four-fermion operators with Neuberger fermions

International Nuclear Information System (INIS)

Dimopoulos, P.; Giusti, L.; Hernandez, P.; Palombi, F.; Pena, C.; Vladikas, A.; Wennekers, J.; Wittig, H.

2006-01-01

We outline a general strategy for the non-perturbative renormalisation of composite operators in discretisations based on Neuberger fermions, via a matching to results obtained with Wilson-type fermions. As an application, we consider the renormalisation of the four-quark operators entering the ΔS=1 and ΔS=2 effective Hamiltonians. Our results are an essential ingredient for the determination of the low-energy constants governing non-leptonic kaon decays

Fermionic counting of RSOS states and Virasoro character formulas for the unitary minimal series M(ν,ν+1): Exact results

International Nuclear Information System (INIS)

Berkovich, Alexander

1994-01-01

The Hilbert space of an RSOS model, introduced by Andrews, Baxter, and Forrester, can be viewed as a space of sequences (paths) {a 0 ,a 1 ,.s, a L }, with a j -integers restricted by 1≤qslanta j ≤qslantν,vertical stroke a j -a j+1 vertical stroke =1,a 0 ≡s, a L ≡r. In this paper we introduce different basis which, as shown here, has the same dimension as that of an RSOS model. This basis appears naturally in the Bethe ansatz calculations of the spin (ν-1)/2 XXZ model. Following McCoy et al., we call this basis fermionic (FB).Our first theorem Dim(FB)=Dim(RSOS-basis) can be succinctly expressed in terms of some identities for binomial coefficients. Remarkably, these binomial identities can be q-deformed. Here, we give a simple proof of these q-binomial identities in the spirit of Schur's proof of the Rogers-Ramanujan identities. Notably, the proof involves only the elementary recurrences for the q-binomial coefficients and a few creative observations.Finally, taking the limit L→∞ in these q-identities, we derive an expression for the character formulas of the unitary minimal series M(ν,ν+1) ''Bosonic Sum ≡ Fermionic Sum''. Here, Bosonic Sum denotes Rocha-Caridi representation (χ r,s=1 ν,ν+1 (q)) and Fermionic Sum stands for the companion representation recently conjectured by the McCoy group. ((orig.))

Generalizing quasinormality

Directory of Open Access Journals (Sweden)

John Cossey

2015-03-01

Full Text Available Quasinormal subgroups have been studied for nearly 80 years. In finite groups, questions concerning them invariably reduce to p-groups, and here they have the added interest of being invariant under projectivities, unlike normal subgroups. However, it has been shown recently that certain groups, constructed by Berger and Gross in 1982, of an important universal nature with regard to the existence of core-free quasinormal subgroups gener- ally, have remarkably few such subgroups. Therefore in order to overcome this misfortune, a generalization of the concept of quasi- normality will be defined. It could be the beginning of a lengthy undertaking. But some of the initial findings are encouraging, in particular the fact that this larger class of subgroups also remains invariant under projectivities of finite p-groups, thus connecting group and subgroup lattice structures.

Entanglement entropy of non-unitary integrable quantum field theory

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Davide Bianchini

2015-07-01

Full Text Available In this paper we study the simplest massive 1+1 dimensional integrable quantum field theory which can be described as a perturbation of a non-unitary minimal conformal field theory: the Lee–Yang model. We are particularly interested in the features of the bi-partite entanglement entropy for this model and on building blocks thereof, namely twist field form factors. Non-unitarity selects out a new type of twist field as the operator whose two-point function (appropriately normalized yields the entanglement entropy. We compute this two-point function both from a form factor expansion and by means of perturbed conformal field theory. We find good agreement with CFT predictions put forward in a recent work involving the present authors. In particular, our results are consistent with a scaling of the entanglement entropy given by ceff3log⁡ℓ where ceff is the effective central charge of the theory (a positive number related to the central charge and ℓ is the size of the region. Furthermore the form factor expansion of twist fields allows us to explore the large region limit of the entanglement entropy and find the next-to-leading order correction to saturation. We find that this correction is very different from its counterpart in unitary models. Whereas in the latter case, it had a form depending only on few parameters of the model (the particle spectrum, it appears to be much more model-dependent for non-unitary models.

Fractionalizing Majorana Fermions: Non-Abelian Statistics on the Edges of Abelian Quantum Hall States

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Netanel H. Lindner

2012-10-01

Full Text Available We study the non-Abelian statistics characterizing systems where counterpropagating gapless modes on the edges of fractional quantum Hall states are gapped by proximity coupling to superconductors and ferromagnets. The most transparent example is that of a fractional quantum spin Hall state, in which electrons of one spin direction occupy a fractional quantum Hall state of ν=1/m, while electrons of the opposite spin occupy a similar state with ν=-1/m. However, we also propose other examples of such systems, which are easier to realize experimentally. We find that each interface between a region on the edge coupled to a superconductor and a region coupled to a ferromagnet corresponds to a non-Abelian anyon of quantum dimension sqrt[2m]. We calculate the unitary transformations that are associated with the braiding of these anyons, and we show that they are able to realize a richer set of non-Abelian representations of the braid group than the set realized by non-Abelian anyons based on Majorana fermions. We carry out this calculation both explicitly and by applying general considerations. Finally, we show that topological manipulations with these anyons cannot realize universal quantum computation.

Index theorem for non-supersymmetric fermions coupled to a non-Abelian string and electric charge quantization

Science.gov (United States)

Shifman, M.; Yung, A.

2018-03-01

Non-Abelian strings are considered in non-supersymmetric theories with fermions in various appropriate representations of the gauge group U(N). We derive the electric charge quantization conditions and the index theorems counting fermion zero modes in the string background both for the left-handed and right-handed fermions. In both cases we observe a non-trivial N dependence.

Nonlocal quasinormal modes for arbitrarily shaped three-dimensional plasmonic resonators

DEFF Research Database (Denmark)

Kamandar Dezfouli, Mohsen; Tserkezis, Christos; Mortensen, N. Asger

2017-01-01

Nonlocal effects have been shown to be responsible for a variety of non-trivial optical effects in small-size plasmonic nanoparticles, beyond classical electrodynamics. However, it is not clear whether optical mode descriptions can be applied to such extreme confinement regimes. Here, we present...... quasinormal modes, even at the single mode level. We exemplify the use of this theory by calculating the Purcell factors of single quantum emitters, the electron energy-loss spectroscopy spatial maps, as well as the Mollow triplet spectra of field-driven quantum dots with and without nonlocal effects...... for different size nanoresonators. Our nonlocal quasinormal mode theory offers a reliable and efficient technique to study both classical and quantum optical problems in nanoplasmonics....

Polynomial approximation of non-Gaussian unitaries by counting one photon at a time

Science.gov (United States)

Arzani, Francesco; Treps, Nicolas; Ferrini, Giulia

2017-05-01

In quantum computation with continuous-variable systems, quantum advantage can only be achieved if some non-Gaussian resource is available. Yet, non-Gaussian unitary evolutions and measurements suited for computation are challenging to realize in the laboratory. We propose and analyze two methods to apply a polynomial approximation of any unitary operator diagonal in the amplitude quadrature representation, including non-Gaussian operators, to an unknown input state. Our protocols use as a primary non-Gaussian resource a single-photon counter. We use the fidelity of the transformation with the target one on Fock and coherent states to assess the quality of the approximate gate.

Quasinormal-Mode Expansion of the Scattering Matrix

Directory of Open Access Journals (Sweden)

Filippo Alpeggiani

2017-06-01

Full Text Available It is well known that the quasinormal modes (or resonant states of photonic structures can be associated with the poles of the scattering matrix of the system in the complex-frequency plane. In this work, the inverse problem, i.e., the reconstruction of the scattering matrix from the knowledge of the quasinormal modes, is addressed. We develop a general and scalable quasinormal-mode expansion of the scattering matrix, requiring only the complex eigenfrequencies and the far-field properties of the eigenmodes. The theory is validated by applying it to illustrative nanophotonic systems with multiple overlapping electromagnetic modes. The examples demonstrate that our theory provides an accurate first-principles prediction of the scattering properties, without the need for postulating ad hoc nonresonant channels.

Boson mappings for elementary excitations in fermion systems

International Nuclear Information System (INIS)

Geyer, H.B.

1981-07-01

The boson mapping formalism is presented with a dual purpose in mind. It is first demonstrated to constitute a microscopic formalism leading to the introduction of collective variables into the many-fermion problem in an exact and consistent manner. Secondly it is shown to present ideal exploring ground with a view to the reconciliation of phenomenological collective nuclear models and microscopic considerations. Of the various existing possibilities for the construction of a boson mapping, we single out the finite, non-unitary Dyson-Maleev mapping, emphasising the convenience of its finiteness, especially in investigations concerning formal aspects of the boson mapping formalism. A contribution to the theory of Dyson-Maleev mappinigs for fermion operators is made by introducing the construction of a consistent mapping for single fermion operators which is free of limitations previously imposed on such a mapping. In various fermion models studies it is shown how the Dyson-Maleev mapping can be utilized to obtain equivalent boson models which, however, can be restricted to yield information about the collective subspace only. As far as phenomenological models are concerned, some new light from a microscopic viewpiont is shed on the assumption underlying the interacting boson model as well as on the calculational procedures usually adopted in this model. The most important observation concerns the assumed structure of the IBM hamiltonian where a non-hermitian form, rather than the existing hermitian form, is indicated

Quasinormal modes of Kerr-de Sitter black holes

International Nuclear Information System (INIS)

Yoshida, Shijun; Uchikata, Nami; Futamase, Toshifumi

2010-01-01

We calculate the fundamental quasinormal modes of the Kerr-de Sitter black hole for the first time. In order to calculate the quasinormal modes, we employ the master equations derived by Suzuki, Takasugi, and Umetsu, who transform the Teukolsky equations for the Kerr-de Sitter black hole into the standard form of the Heun's equation. The transformed functions are expanded around the outer horizon of the black hole or the symmetric axis in the Froebenius series whose coefficients satisfy a three-term recurrence relation. These three-term recurrence relations allow us to use Leaver's continued fraction method to calculate the angular separation constant and the quasinormal mode frequency. Any unstable fundamental quasinormal mode is not found in this paper. It is also observed that for some black holes characterized by a large mass parameter, some retrograde modes in the slow rotation limit become prograde as the black hole spin increases. This phenomenon does not occur for the fundamental modes of the Kerr black hole.

Efficient Nonlocal M-Control and N-Target Controlled Unitary Gate Using Non-symmetric GHZ States

Science.gov (United States)

Chen, Li-Bing; Lu, Hong

2018-03-01

Efficient local implementation of a nonlocal M-control and N-target controlled unitary gate is considered. We first show that with the assistance of two non-symmetric qubit(1)-qutrit(N) Greenberger-Horne-Zeilinger (GHZ) states, a nonlocal 2-control and N-target controlled unitary gate can be constructed from 2 local two-qubit CNOT gates, 2 N local two-qutrit conditional SWAP gates, N local qutrit-qubit controlled unitary gates, and 2 N single-qutrit gates. At each target node, the two third levels of the two GHZ target qutrits are used to expose one and only one initial computational state to the local qutrit-qubit controlled unitary gate, instead of being used to hide certain states from the conditional dynamics. This scheme can be generalized straightforwardly to implement a higher-order nonlocal M-control and N-target controlled unitary gate by using M non-symmetric qubit(1)-qutrit(N) GHZ states as quantum channels. Neither the number of the additional levels of each GHZ target particle nor that of single-qutrit gates needs to increase with M. For certain realistic physical systems, the total gate time may be reduced compared with that required in previous schemes.

Mesonic quasinormal modes of the Sakai-Sugimoto model at high temperature

International Nuclear Information System (INIS)

Evans, Nick; Threlfall, Ed

2008-01-01

We examine the mesonic thermal spectrum of the Sakai-Sugimoto model of holographic QCD by finding the quasinormal frequencies of the supergravity dual. If flavor is added using D8-D8 branes there exist embeddings where the D-brane world volume contains a black hole. For these embeddings (the high-temperature phase of the Sakai-Sugimoto model) we determine the quasinormal spectra of scalar and vector mesons arising from the world volume Dirac-Born-Infeld (DBI) action of the D-brane. We stress the importance of a coordinate change that makes the infalling quasinormal modes regular at the horizon allowing a simple numerical shooting technique. Finally we examine the effect of finite spatial momentum on quasinormal spectra

Quasinormal modes of semiclassical electrically charged black holes

Energy Technology Data Exchange (ETDEWEB)

Fernandez Piedra, Owen Pavel [Departamento de Fisica y Quimica, Facultad de Mecanica, Universidad de Cienfuegos, Carretera a Rodas, km 4, Cuatro Caminos, Cienfuegos (Cuba); De Oliveira, Jeferson, E-mail: opavel@ucf.edu.cu, E-mail: jeferson@fma.if.usp.br [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970, Sao Paulo (Brazil)

2011-04-21

We report the results concerning the influence of vacuum polarization due to quantum massive vector, scalar and spinor fields on the scalar sector of quasinormal modes in spherically symmetric charged black holes. The vacuum polarization from quantized fields produces a shift in the values of the quasinormal frequencies, and correspondingly the semiclassical system becomes a better oscillator with respect to the classical Reissner-Nordstroem black hole.

Perturbations and quasi-normal modes of black holes in Einstein-Aether theory

International Nuclear Information System (INIS)

Konoplya, R.A.; Zhidenko, A.

2007-01-01

We develop a new method for calculation of quasi-normal modes of black holes, when the effective potential, which governs black hole perturbations, is known only numerically in some region near the black hole. This method can be applied to perturbations of a wide class of numerical black hole solutions. We apply it to the black holes in the Einstein-Aether theory, a theory where general relativity is coupled to a unit time-like vector field, in order to observe local Lorentz symmetry violation. We found that in the non-reduced Einstein-Aether theory, real oscillation frequency and damping rate of quasi-normal modes are larger than those of Schwarzschild black holes in the Einstein theory

Fermion-dyon dynamics in non-Abelian gauge theory

International Nuclear Information System (INIS)

Pant, P.C.; Pandey, V.P.; Rajput, B.S.

1999-01-01

The study of behaviour of a fermion in the field of non-Abelian dyon has been undertaken in Lagrangian and Hamiltonian formulation. Solving Dirac equation, expression for energy Eigen value has been obtained and the Hamiltonian of this system has been shown to involve spin as well as contribution of massive fields associated with these particles. By introducing suitable spinors, the Pauli equation for a dyon moving in the field of fermion has been solved in non-Abelian gauge gauge theory and it is shown that introduction of massive fields perceptibly modifies the energy Eigen value and Eigen function of bound states of the system. (author)

On the chirality of the SM and the fermion content of GUTs

Directory of Open Access Journals (Sweden)

Renato M. Fonseca

2015-08-01

Full Text Available The Standard Model (SM is a chiral theory, where right- and left-handed fermion fields transform differently under the gauge group. Extra fermions, if they do exist, need to be heavy otherwise they would have already been observed. With no complex mechanisms at work, such as confining interactions or extra-dimensions, this can only be achieved if every extra right-handed fermion comes paired with a left-handed one transforming in the same way under the Standard Model gauge group, otherwise the new states would only get a mass after electroweak symmetry breaking, which would necessarily be small (∼100 GeV. Such a simple requirement severely constrains the fermion content of Grand Unified Theories (GUTs. It is known for example that three copies of the representations 5¯+10 of SU(5 or three copies of the 16 of SO(10 can reproduce the Standard Model's chirality, but how unique are these arrangements? In a systematic way, this paper looks at the possibility of having non-standard mixtures of fermion GUT representations yielding the correct Standard Model chirality. Family unification is possible with large special unitary groups — for example, the 171 representation of SU(19 may decompose as 3(16+120+3(1 under SO(10.

Exact gravitational quasinormal frequencies of topological black holes

International Nuclear Information System (INIS)

Birmingham, Danny; Mokhtari, Susan

2006-01-01

We compute the exact gravitational quasinormal frequencies for massless topological black holes in d-dimensional anti-de Sitter space. Using the gauge invariant formalism for gravitational perturbations derived by Kodama and Ishibashi, we show that in all cases the scalar, vector, and tensor modes can be reduced to a simple scalar field equation. This equation is exactly solvable in terms of hypergeometric functions, thus allowing an exact analytic determination of the gravitational quasinormal frequencies

Are eikonal quasinormal modes linked to the unstable circular null geodesics?

Directory of Open Access Journals (Sweden)

R.A. Konoplya

2017-08-01

Full Text Available In Cardoso et al. [6] it was claimed that quasinormal modes which any stationary, spherically symmetric and asymptotically flat black hole emits in the eikonal regime are determined by the parameters of the circular null geodesic: the real and imaginary parts of the quasinormal mode are multiples of the frequency and instability timescale of the circular null geodesics respectively. We shall consider asymptotically flat black hole in the Einstein–Lovelock theory, find analytical expressions for gravitational quasinormal modes in the eikonal regime and analyze the null geodesics. Comparison of the both phenomena shows that the expected link between the null geodesics and quasinormal modes is violated in the Einstein–Lovelock theory. Nevertheless, the correspondence exists for a number of other cases and here we formulate its actual limits.

Are eikonal quasinormal modes linked to the unstable circular null geodesics?

Science.gov (United States)

Konoplya, R. A.; Stuchlík, Z.

2017-08-01

In Cardoso et al. [6] it was claimed that quasinormal modes which any stationary, spherically symmetric and asymptotically flat black hole emits in the eikonal regime are determined by the parameters of the circular null geodesic: the real and imaginary parts of the quasinormal mode are multiples of the frequency and instability timescale of the circular null geodesics respectively. We shall consider asymptotically flat black hole in the Einstein-Lovelock theory, find analytical expressions for gravitational quasinormal modes in the eikonal regime and analyze the null geodesics. Comparison of the both phenomena shows that the expected link between the null geodesics and quasinormal modes is violated in the Einstein-Lovelock theory. Nevertheless, the correspondence exists for a number of other cases and here we formulate its actual limits.

Hybrid Monte Carlo algorithm with fat link fermion actions

International Nuclear Information System (INIS)

Kamleh, Waseem; Leinweber, Derek B.; Williams, Anthony G.

2004-01-01

The use of APE smearing or other blocking techniques in lattice fermion actions can provide many advantages. There are many variants of these fat link actions in lattice QCD currently, such as flat link irrelevant clover (FLIC) fermions. The FLIC fermion formalism makes use of the APE blocking technique in combination with a projection of the blocked links back into the special unitary group. This reunitarization is often performed using an iterative maximization of a gauge invariant measure. This technique is not differentiable with respect to the gauge field and thus prevents the use of standard Hybrid Monte Carlo simulation algorithms. The use of an alternative projection technique circumvents this difficulty and allows the simulation of dynamical fat link fermions with standard HMC and its variants. The necessary equations of motion for FLIC fermions are derived, and some initial simulation results are presented. The technique is more general however, and is straightforwardly applicable to other smearing techniques or fat link actions

Renormalization of fermion mixing

International Nuclear Information System (INIS)

Schiopu, R.

2007-01-01

hermiticity. After analysing the complete renormalized Lagrangian in a general theory including vector and scalar bosons with arbitrary renormalizable interactions, we consider two specific models: quark mixing in the electroweak Standard Model and mixing of Majorana neutrinos in the seesaw mechanism. A counter term for fermion mixing matrices can not be fixed by only taking into account self-energy corrections or fermion field renormalization constants. The presence of unstable particles in the theory can lead to a non-unitary renormalized mixing matrix or to a gauge parameter dependence in its counter term. Therefore, we propose to determine the mixing matrix counter term by fixing the complete correction terms for a physical process to experimental measurements. As an example, we calculate the decay rate of a top quark and of a heavy neutrino. We provide in each of the chosen models sample calculations that can be easily extended to other theories. (orig.)

Renormalization of fermion mixing

Energy Technology Data Exchange (ETDEWEB)

Schiopu, R.

2007-05-11

hermiticity. After analysing the complete renormalized Lagrangian in a general theory including vector and scalar bosons with arbitrary renormalizable interactions, we consider two specific models: quark mixing in the electroweak Standard Model and mixing of Majorana neutrinos in the seesaw mechanism. A counter term for fermion mixing matrices can not be fixed by only taking into account self-energy corrections or fermion field renormalization constants. The presence of unstable particles in the theory can lead to a non-unitary renormalized mixing matrix or to a gauge parameter dependence in its counter term. Therefore, we propose to determine the mixing matrix counter term by fixing the complete correction terms for a physical process to experimental measurements. As an example, we calculate the decay rate of a top quark and of a heavy neutrino. We provide in each of the chosen models sample calculations that can be easily extended to other theories. (orig.)

Non-unitary neutrino mixing and CP violation in the minimal inverse seesaw model

International Nuclear Information System (INIS)

Malinsky, Michal; Ohlsson, Tommy; Xing, Zhi-zhong; Zhang He

2009-01-01

We propose a simplified version of the inverse seesaw model, in which only two pairs of the gauge-singlet neutrinos are introduced, to interpret the observed neutrino mass hierarchy and lepton flavor mixing at or below the TeV scale. This 'minimal' inverse seesaw scenario (MISS) is technically natural and experimentally testable. In particular, we show that the effective parameters describing the non-unitary neutrino mixing matrix are strongly correlated in the MISS, and thus, their upper bounds can be constrained by current experimental data in a more restrictive way. The Jarlskog invariants of non-unitary CP violation are calculated, and the discovery potential of such new CP-violating effects in the near detector of a neutrino factory is discussed.

Wormhole potentials and throats from quasi-normal modes

Science.gov (United States)

Völkel, Sebastian H.; Kokkotas, Kostas D.

2018-05-01

Exotic compact objects refer to a wide class of black hole alternatives or effective models to describe phenomenologically quantum gravitational effects on the horizon scale. In this work we show how the knowledge of the quasi-normal mode spectrum of non-rotating wormhole models can be used to reconstruct the effective potential that appears in perturbation equations. From this it is further possible to obtain the parameters that characterize the specific wormhole model, which in this paper was chosen to be the one by Damour and Solodukhin. We also address the question whether one can distinguish such type of wormholes from ultra compact stars, if only the quasi-normal mode spectrum is known. We have proven that this is not possible by using the trapped modes only, but requires additional information. The inverse method presented here is an extension of work that has previously been developed and applied to the oscillation spectra of ultra compact stars and gravastars. However, it is not limited to the study of exotic compact objects, but applicable to symmetric double barrier potentials that appear in one-dimensional wave equations. Therefore we think it can be of interest for other fields too.

Exact quasinormal modes for a special class of black holes

International Nuclear Information System (INIS)

Oliva, Julio; Troncoso, Ricardo

2010-01-01

Analytic exact expressions for the quasinormal modes of scalar and electromagnetic perturbations around a special class of black holes are found in d≥3 dimensions. It is shown that the size of the black hole provides a lower bound for the angular momentum of the perturbation. Quasinormal modes appear when this bound is fulfilled; otherwise the excitations become purely damped.

Radiative seesaw-type mechanism of fermion masses and non-trivial quark mixing

Energy Technology Data Exchange (ETDEWEB)

Arbelaez, Carolina; Hernandez, A.E.C.; Kovalenko, Sergey; Schmidt, Ivan [Universidad Tecnica Federico Santa Maria, Centro Cientifico-Tecnologico de Valparaiso-CCTVal, Valparaiso (Chile)

2017-06-15

We propose a predictive inert two-Higgs doublet model, where the standard model (SM) symmetry is extended by S{sub 3} x Z{sub 2} x Z{sub 12} and the field content is enlarged by extra scalar fields, charged exotic fermions and two heavy right-handed Majorana neutrinos. The charged exotic fermions generate a non-trivial quark mixing and provide one-loop-level masses for the first- and second-generation charged fermions. The masses of the light active neutrinos are generated from a one-loop-level radiative seesaw mechanism. Our model successfully explains the observed SM fermion mass and mixing pattern. (orig.)

Quasinormal modes of Gauss-Bonnet black holes at large D

Energy Technology Data Exchange (ETDEWEB)

Chen, Bin [Department of Physics and State Key Laboratory of Nuclear Physics and Technology,Peking University,No. 5 Yiheyuan Rd, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter,No. 5 Yiheyuan Rd, Beijing 100871 (China); Center for High Energy Physics, Peking University,No. 5 Yiheyuan Rd, Beijing 100871 (China); Fan, Zhong-Ying [Center for High Energy Physics, Peking University,No. 5 Yiheyuan Rd, Beijing 100871 (China); Li, Pengcheng; Ye, Weicheng [Department of Physics and State Key Laboratory of Nuclear Physics and Technology,Peking University,No. 5 Yiheyuan Rd, Beijing 100871 (China)

2016-01-15

Einstein’s General Relativity theory simplifies dramatically in the limit that the spacetime dimension D is very large. This could still be true in the gravity theory with higher derivative terms. In this paper, as the first step to study the gravity with a Gauss-Bonnet(GB) term, we compute the quasi-normal modes of the spherically symmetric GB black hole in the large D limit. When the GB parameter is small, we find that the non-decoupling modes are the same as the Schwarzschild case and the decoupled modes are slightly modified by the GB term. However, when the GB parameter is large, we find some novel features. We notice that there are another set of non-decoupling modes due to the appearance of a new plateau in the effective radial potential. Moreover, the effective radial potential for the decoupled vector-type and scalar-type modes becomes more complicated. Nevertheless we manage to compute the frequencies of the these decoupled modes analytically. When the GB parameter is neither very large nor very small, though analytic computation is not possible, the problem is much simplified in the large D expansion and could be numerically treated. We study numerically the vector-type quasinormal modes in this case.

Quasinormal modes of a strongly coupled nonconformal plasma and approach to criticality

Science.gov (United States)

Betzios, Panagiotis; Gürsoy, Umut; Järvinen, Matti; Policastro, Giuseppe

2018-04-01

We study fluctuations around equilibrium in a class of strongly interacting nonconformal plasmas using holographic techniques. In particular, we calculate the quasinormal mode spectrum of black hole backgrounds that approach Chamblin-Reall plasmas in the IR. In a specific limit, related to the exact linear-dilaton background in string theory, we observe that the plasma approaches criticality and we obtain the quasinormal spectrum analytically. We regulate the critical limit by gluing the IR geometry that corresponds to the nonconformal plasma to a part of AdS space-time in the UV. Near criticality, the spectrum can still be computed analytically and we find two sets of quasinormal modes, related to the IR and UV parts of the geometry. In the critical limit, the quasinormal modes accumulate to form a branch cut in the correlators of the energy-momentum tensor on the real axis of the complex frequency plane.

Canonical form of three-fermion pure-states with six single particle states

International Nuclear Information System (INIS)

Chen, Lin; Ž Ðoković, Dragomir; Grassl, Markus; Zeng, Bei

2014-01-01

We construct a canonical form for pure states in ∧ 3 (C 6 ), the three-fermion system with six single particle states, under local unitary (LU) transformations, i.e., the unitary group U(6). We also construct a minimal set of generators of the algebra of polynomial U(6)-invariants on ∧ 3 (C 6 ). It turns out that this algebra is isomorphic to the algebra of polynomial LU-invariants of three-qubits which are additionally invariant under qubit permutations. As a consequence of this surprising fact, we deduce that there is a one-to-one correspondence between the U(6)-orbits of pure three-fermion states in ∧ 3 (C 6 ) and the LU orbits of pure three-qubit states when qubit permutations are allowed. As an important byproduct, we obtain a new canonical form for pure three-qubit states under LU transformations U(2) × U(2) × U(2) (no qubit permutations allowed)

Towards a Complete Classification of Symmetry-Protected Topological Phases for Interacting Fermions in Three Dimensions and a General Group Supercohomology Theory

Science.gov (United States)

Wang, Qing-Rui; Gu, Zheng-Cheng

2018-01-01

The classification and construction of symmetry-protected topological (SPT) phases in interacting boson and fermion systems have become a fascinating theoretical direction in recent years. It has been shown that (generalized) group cohomology theory or cobordism theory gives rise to a complete classification of SPT phases in interacting boson or spin systems. The construction and classification of SPT phases in interacting fermion systems are much more complicated, especially in three dimensions. In this work, we revisit this problem based on an equivalence class of fermionic symmetric local unitary transformations. We construct very general fixed-point SPT wave functions for interacting fermion systems. We naturally reproduce the partial classifications given by special group supercohomology theory, and we show that with an additional B ˜H2(Gb,Z2) structure [the so-called obstruction-free subgroup of H2(Gb,Z2) ], a complete classification of SPT phases for three-dimensional interacting fermion systems with a total symmetry group Gf=Gb×Z2f can be obtained for unitary symmetry group Gb. We also discuss the procedure for deriving a general group supercohomology theory in arbitrary dimensions.

Quasinormal modes of asymptotically (A)dS black hole in Lovelock background

Science.gov (United States)

Abbasvandi, N.; Soleimani, M. J.; Abdullah, W. A. T. Wan; Radiman, Shahidan

2017-03-01

We study the quasinormal modes of the massless scalar field in asymptotically (A)dS black holes in Lovelock spacetime by using the sixth order of the WKB approximation. We consider the effects of the second and third order of Lovelock coupling constants on quasinormal frequencies spectrum as well as cosmological constant.

Quasi-normal frequencies: Semi-analytic results for highly damped modes

International Nuclear Information System (INIS)

Skakala, Jozef; Visser, Matt

2011-01-01

Black hole highly-damped quasi-normal frequencies (QNFs) are very often of the form ω n = (offset) + in (gap). We have investigated the genericity of this phenomenon for the Schwarzschild-deSitter (SdS) black hole by considering a model potential that is piecewise Eckart (piecewise Poschl-Teller), and developing an analytic 'quantization condition' for the highly-damped quasi-normal frequencies. We find that the ω n = (offset) + in (gap) behaviour is common but not universal, with the controlling feature being whether or not the ratio of the surface gravities is a rational number. We furthermore observed that the relation between rational ratios of surface gravities and periodicity of QNFs is very generic, and also occurs within different analytic approaches applied to various types of black hole spacetimes. These observations are of direct relevance to any physical situation where highly-damped quasi-normal modes are important.

Numerical study of the quasinormal mode excitation of Kerr black holes

International Nuclear Information System (INIS)

Dorband, Ernst Nils; Diener, Peter; Tiglio, Manuel; Berti, Emanuele; Schnetter, Erik

2006-01-01

We present numerical results from three-dimensional evolutions of scalar perturbations of Kerr black holes. Our simulations make use of a high-order accurate multiblock code which naturally allows for adapted grids and smooth inner (excision) and outer boundaries. We focus on the quasinormal ringing phase, presenting a systematic method for extraction of the quasinormal mode frequencies and amplitudes and comparing our results against perturbation theory. The detection of a single mode in a ringdown waveform allows for a measurement of the mass and spin of a black hole; a multimode detection would allow a test of the Kerr nature of the source. Since the possibility of a multimode detection depends on the relative mode amplitude, we study this topic in some detail. The amplitude of each mode depends exponentially on the starting time of the quasinormal regime, which is not defined unambiguously. We show that this time-shift problem can be circumvented by looking at appropriately chosen relative mode amplitudes. From our simulations we extract the quasinormal frequencies and the relative and absolute amplitudes of corotating and counterrotating modes (including overtones in the corotating case). We study the dependence of these amplitudes on the shape of the initial perturbation, the angular dependence of the mode, and the black hole spin, comparing against results from perturbation theory in the so-called asymptotic approximation. We also compare the quasinormal frequencies from our numerical simulations with predictions from perturbation theory, finding excellent agreement. For rapidly rotating black holes (of spin j=0.98) we can extract the quasinormal frequencies of not only the fundamental mode, but also of the first two overtones. Finally we study under what conditions the relative amplitude between given pairs of modes gets maximally excited and present a quantitative analysis of rotational mode-mode coupling. The main conclusions and techniques of our

Stability condition of a strongly interacting boson-fermion mixture across an interspecies Feshbach resonance

International Nuclear Information System (INIS)

Yu Zengqiang; Zhai Hui; Zhang Shizhong

2011-01-01

We study the properties of dilute bosons immersed in a single-component Fermi sea across a broad boson-fermion Feshbach resonance. The stability of the mixture requires that the bare interaction between bosons exceeds a critical value, which is a universal function of the boson-fermion scattering length, and exhibits a maximum in the unitary region. We calculate the quantum depletion, momentum distribution, and the boson contact parameter across the resonance. The transition from condensate to molecular Fermi gas is also discussed.

Quasinormal modes of Schwarzschild black holes: Defined and calculated via Laplace transformation

International Nuclear Information System (INIS)

Nollert, H.; Schmidt, B.G.

1992-01-01

Quasinormal modes play a prominent role in the literature when dealing with the propagation of linearized perturbations of the Schwarzschild geometry. We show that space-time properties of the solutions of the perturbation equation imply the existence of a unique Green's function of the Laplace-transformed wave equation. This Green's function may be constructed from solutions of the homogeneous time-independent equation, which are uniquely characterized by the boundary conditions they satisfy. These boundary conditions are identified as the boundary conditions usually imposed for quasinormal-mode solutions. It turns out that solutions of the homogeneous equation exist which satisfy these boundary conditions at the horizon and at spatial infinity simultaneously, leading to poles of the Green's function. We therefore propose to define quasinormal-mode frequencies as the poles of the Green's function for the Laplace-transformed equation. On the basis of this definition a new technique for the numerical calculation of quasinormal frequencies is developed. The results agree with computations of Leaver, but not with more recent results obtained by Guinn, Will, Kojima, and Schutz

Multipartite entanglement in fermionic systems via a geometric measure

International Nuclear Information System (INIS)

Lari, Behzad; Durganandini, P.; Joag, Pramod S.

2010-01-01

We study multipartite entanglement in a system consisting of indistinguishable fermions. Specifically, we have proposed a geometric entanglement measure for N spin-(1/2) fermions distributed over 2L modes (single-particle states). The measure is defined on the 2L qubit space isomorphic to the Fock space for 2L single-particle states. This entanglement measure is defined for a given partition of 2L modes containing m≥2 subsets. Thus this measure applies to m≤2L partite fermionic systems where L is any finite number, giving the number of sites. The Hilbert spaces associated with these subsets may have different dimensions. Further, we have defined the local quantum operations with respect to a given partition of modes. This definition is generic and unifies different ways of dividing a fermionic system into subsystems. We have shown, using a representative case, that the geometric measure is invariant under local unitary operators corresponding to a given partition. We explicitly demonstrate the use of the measure to calculate multipartite entanglement in some correlated electron systems.

Perturbative calculation of quasinormal modes of AdS Schwarzschild black holes

International Nuclear Information System (INIS)

Musiri, Suphot; Ness, Scott; Siopsis, George

2006-01-01

We calculate analytically quasinormal modes of AdS Schwarzschild black holes including first-order corrections. We consider massive scalar, gravitational and electromagnetic perturbations. Our results are in good agreement with numerical calculations. In the case of electromagnetic perturbations, ours is the first calculation to provide an analytic expression for quasinormal frequencies, because the effective potential vanishes at zeroth order. We show that the first-order correction is logarithmic

Thermodynamics, phase transition and quasinormal modes with Weyl corrections

Energy Technology Data Exchange (ETDEWEB)

Mahapatra, Subhash [The Institute of Mathematical Sciences,Chennai 600113 (India)

2016-04-21

We study charged black holes in D dimensional AdS space, in the presence of four derivative Weyl correction. We obtain the black hole solution perturbatively up to first as well as second order in the Weyl coupling, and show that first law of black hole thermodynamics is satisfied in all dimensions. We study its thermodynamic phase transition and then calculate the quasinormal frequencies of the massless scalar field perturbation. We find that, here too, the quasinormal frequencies capture the essence of black hole phase transition. Few subtleties near the second order critical point are discussed.

A contribution to the study of fermions and of their mixing angles in Quantum Field Theory

International Nuclear Information System (INIS)

Duret, Q.

2008-09-01

This thesis is divided into two parts. The first one is devoted to the study of the fermion mixing angles in Quantum Field Theory (QFT). We show that, due to the non-ortho-normality of its mass eigenstates, the mixing matrix of a non-degenerate system of coupled fermions cannot be considered a priori to be unitary; then, in the standard model framework, that all mixing angles of quarks and leptons are consistent with a precise structure of neutral currents, in which universality and absence of flavour changing currents are equally violated. This scheme yields the quark-lepton complementarity relation between the Cabibbo angle and the second mixing angle of neutrinos. We also recover perturbatively the non unitarity of the mixing matrix by canceling nondiagonal one-loop transitions between mass eigenstates, and show how the gauge symmetry nevertheless guarantees the unitarity of the Cabibbo matrix which occurs in renormalized gauge currents. We finally study the flavour transformations that are relevant in this procedure, and outline a link between the neutral currents and the mass matrix usually considered for coupled systems. The second part presents the first results of a general study of the constraints cast in QFT by the discrete symmetries (parity P, charge conjugation C and time reversal T) on the fermionic Lagrangian and propagator. We show for one generation that the latter, being written in the most general way compatible with Lorentz invariance, are naturally PCT-invariant, and that the eigenstates of a C-invariant propagator are Majorana fermions. (author)

On random unitary channels

International Nuclear Information System (INIS)

Audenaert, Koenraad M R; Scheel, Stefan

2008-01-01

In this paper, we provide necessary and sufficient conditions for a completely positive trace-preserving (CPT) map to be decomposable into a convex combination of unitary maps. Additionally, we set out to define a proper distance measure between a given CPT map and the set of random unitary maps, and methods for calculating it. In this way one could determine whether non-classical error mechanisms such as spontaneous decay or photon loss dominate over classical uncertainties, for example, in a phase parameter. The present paper is a step towards achieving this goal

A Bloch mode expansion approach for analyzing quasi-normal modes in open nanophotonic structures

DEFF Research Database (Denmark)

de Lasson, Jakob Rosenkrantz; Kristensen, Philip Trøst; Mørk, Jesper

2014-01-01

We present a new method for determining quasi-normal modes in open nanophotonic structures using a modal ex- pansion technique. The outgoing wave boundary condition of the quasi-normal modes is satisfied automatically without absorbing boundaries, representing a significant advantage compared...

Interacting fermions in one spatial dimensions

International Nuclear Information System (INIS)

Wolf, D.

1982-01-01

This thesis contains in its first part a critical survey about the method of the bosonization of fermi fields in one spatial dimension and its application to the Luttinger and the massive Thirring model. The first chapter served for the explanation of the term of the unitary inequivalence. Thereby two generally valid facts could be demonstrated very illustratively by the example of a fermion algebra and its representations, namely first that infinite, direct product space are not separable, and second that weak equivalence of the vacua is equivalent to the unitary equivalence of the corresponding representations of the field algebra. In the second part the statement first studied by Luther (1976) and since then often cited, that the continuum limit of the Heisenberg model is the massive Thirring model. It is concluded that it can up to today not be considered as proved although indications for its validity can be found. (orig./HSI) [de

Quasinormal modes of the near extremal Schwarzschild-de Sitter black hole

International Nuclear Information System (INIS)

Cardoso, Vitor; Lemos, Jose P.S.

2003-01-01

We present an exact expression for the quasinormal modes of scalar, electromagnetic, and gravitational perturbations of a near extremal Schwarzschild-de Sitter black hole and we show that is why a previous approximation holds exactly in this near extremal regime. In particular, our results give the asymptotic behavior of the quasinormal frequencies for highly damped modes, which has recently attracted much attention due to the proposed identification of its real part with the Barbero-Immirzi parameter

Black-hole quasinormal resonances: Wave analysis versus a geometric-optics approximation

International Nuclear Information System (INIS)

Hod, Shahar

2009-01-01

It has long been known that null unstable geodesics are related to the characteristic modes of black holes--the so-called quasinormal resonances. The basic idea is to interpret the free oscillations of a black hole in the eikonal limit in terms of null particles trapped at the unstable circular orbit and slowly leaking out. The real part of the complex quasinormal resonances is related to the angular velocity at the unstable null geodesic. The imaginary part of the resonances is related to the instability time scale (or the inverse Lyapunov exponent) of the orbit. While this geometric-optics description of the black-hole quasinormal resonances in terms of perturbed null rays is very appealing and intuitive, it is still highly important to verify the validity of this approach by directly analyzing the Teukolsky wave equation which governs the dynamics of perturbation waves in the black-hole spacetime. This is the main goal of the present paper. We first use the geometric-optics technique of perturbing a bundle of unstable null rays to calculate the resonances of near-extremal Kerr black holes in the eikonal approximation. We then directly solve the Teukolsky wave equation (supplemented by the appropriate physical boundary conditions) and show that the resultant quasinormal spectrum obtained directly from the wave analysis is in accord with the spectrum obtained from the geometric-optics approximation of perturbed null rays.

Kondo lattice model: Unitary transformations, spin dynamics, strongly correlated charged modes, and vacuum instability

OpenAIRE

Prats, J. M.; Lopez-Aguilar, F.

1996-01-01

Using unitary transformations, we express the Kondo lattice Hamiltonian in terms of fermionic operators that annihilate the ground state of the interacting system and that represent the best possible approximations to the actual charged excitations. In this way, we obtain an effective Hamiltonian which, for small couplings, consists in a kinetic term for conduction electrons and holes, an RKKY-like term, and a renormalized Kondo interaction. The physical picture of the system implied by this ...

Second-order transport, quasinormal modes and zero-viscosity limit in the Gauss-Bonnet holographic fluid

Energy Technology Data Exchange (ETDEWEB)

Grozdanov, Sašo [Instituut-Lorentz for Theoretical Physics, Leiden University, Niels Bohrweg 2, Leiden 2333 CA (Netherlands); Starinets, Andrei O. [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)

2017-03-30

Gauss-Bonnet holographic fluid is a useful theoretical laboratory to study the effects of curvature-squared terms in the dual gravity action on transport coefficients, quasinormal spectra and the analytic structure of thermal correlators at strong coupling. To understand the behavior and possible pathologies of the Gauss-Bonnet fluid in 3+1 dimensions, we compute (analytically and non-perturbatively in the Gauss-Bonnet coupling) its second-order transport coefficients, the retarded two- and three-point correlation functions of the energy-momentum tensor in the hydrodynamic regime as well as the relevant quasinormal spectrum. The Haack-Yarom universal relation among the second-order transport coefficients is violated at second order in the Gauss-Bonnet coupling. In the zero-viscosity limit, the holographic fluid still produces entropy, while the momentum diffusion and the sound attenuation are suppressed at all orders in the hydrodynamic expansion. By adding higher-derivative electromagnetic field terms to the action, we also compute corrections to charge diffusion and identify the non-perturbative parameter regime in which the charge diffusion constant vanishes.

Quasinormal modes for massless topological black holes

International Nuclear Information System (INIS)

Aros, Rodrigo; Martinez, Cristian; Troncoso, Ricardo; Zanelli, Jorge

2003-01-01

An exact expression for the quasinormal modes of scalar perturbation on a massless topological black hole in four and higher dimensions is presented. The massive scalar field is nonminimally coupled to the curvature, and the horizon geometry is assumed to have a negative constant curvature

C{sub T} for non-unitary CFTs in higher dimensions

Energy Technology Data Exchange (ETDEWEB)

Osborn, Hugh [Department of Applied Mathematics and Theoretical Physics, Wilberforce Road,Cambridge CB3 0WA, England (United Kingdom); Stergiou, Andreas [Department of Physics, Yale University,New Haven, CT 06520 (United States)

2016-06-13

The coefficient C{sub T} of the conformal energy-momentum tensor two-point function is determined for the non-unitary scalar CFTs with four- and six-derivative kinetic terms. The results match those expected from large-N calculations for the CFTs arising from the O(N) non-linear sigma and Gross-Neveu models in specific even dimensions. C{sub T} is also calculated for the CFT arising from (n−1)-form gauge fields with derivatives in 2n+2 dimensions. Results for (n−1)-form theory extended to general dimensions as a non-gauge-invariant CFT are also obtained; the resulting C{sub T} differs from that for the gauge-invariant theory. The construction of conformal primaries by subtracting descendants of lower-dimension primaries is also discussed. For free theories this also leads to an alternative construction of the energy-momentum tensor, which can be quite involved for higher-derivative theories.

Lifshitz quasinormal modes and relaxation from holography

NARCIS (Netherlands)

Sybesma, Watse|info:eu-repo/dai/nl/369283074; Vandoren, Stefan|info:eu-repo/dai/nl/304830739

2015-01-01

We obtain relaxation times for field theories with Lifshitz scaling and with holographic duals Einstein-Maxwell-Dilaton gravity theories. This is done by computing quasinormal modes of a bulk scalar field in the presence of Lifshitz black branes. We determine the relation between relaxation time and

Evenly distributed unitaries: On the structure of unitary designs

International Nuclear Information System (INIS)

Gross, D.; Audenaert, K.; Eisert, J.

2007-01-01

We clarify the mathematical structure underlying unitary t-designs. These are sets of unitary matrices, evenly distributed in the sense that the average of any tth order polynomial over the design equals the average over the entire unitary group. We present a simple necessary and sufficient criterion for deciding if a set of matrices constitutes a design. Lower bounds for the number of elements of 2-designs are derived. We show how to turn mutually unbiased bases into approximate 2-designs whose cardinality is optimal in leading order. Designs of higher order are discussed and an example of a unitary 5-design is presented. We comment on the relation between unitary and spherical designs and outline methods for finding designs numerically or by searching character tables of finite groups. Further, we sketch connections to problems in linear optics and questions regarding typical entanglement

Fermions in interaction with time dependent fields

International Nuclear Information System (INIS)

Falkensteiner, P.; Grosse, H.

1988-01-01

We solve a two dimensional model describing the interaction of fermions with time dependent external fields. We work out the second quantized formulation and obtain conditions for equivalence of representations at different times. This implies the existence of sectors which describe charged states. We obtain the time dependence of charges and observe that charge differences become integer for unitary equivalent states. For scattering we require the equivalence of in- and out-representations; nevertheless charged sectors may be reached by suitable interactions and ionization is possible. 20 refs. (Author)

Unitary Quantum Relativity. (Work in Progress)

Science.gov (United States)

Finkelstein, David Ritz

2017-01-01

A quantum universe is expressed as a finite unitary relativistic quantum computer network. Its addresses are subject to quantum superposition as well as its memory. It has no exact mathematical model. It Its Hilbert space of input processes is also a Clifford algebra with a modular architecture of many ranks. A fundamental fermion is a quantum computer element whose quantum address belongs to the rank below. The least significant figures of its address define its spin and flavor. The most significant figures of it adress define its orbital variables. Gauging arises from the same quantification as space-time. This blurs star images only slightly, but perhaps measurably. General relativity is an approximation that splits nature into an emptiness with a high symmetry that is broken by a filling of lower symmetry. Action principles result from self-organization pf the vacuum.

b-τ unification with gaugino and s fermion mass non-universality

International Nuclear Information System (INIS)

Pallis, C.

2004-01-01

In the context of a SUSY GUT inspired MSSM version, the low energy consequences of the asymptotic b-τ Yukawa coupling unification are examined, under the assumption of universal or non-universal boundary conditions for the gaugino and s fermion masses. Gaugino non-universality is applied, so that the SUSY corrections to b-quark mass can be reconciled with the present experimental data on muon anomalous magnetic moment. Restrictions on the parameter space, originating from the cold dark matter abundance in the universe, the inclusive branching ratio of b→sγ and the accelerator data are, also, investigated and the scalar neutralino-proton cross section is calculated. In the case of a bino-like LSP and universal boundary conditions for the s fermion masses, the constraints, arising from the cold dark matter and BR(b→sγ) can be simultaneously satisfied, mainly thanks to the A-pole effect or the neutralino-stau coannihilations. In addition, s fermion mass non-universality provides the possibility of new coannihilation phenomena (neutralino-sbottom or neutralino-tau sneutrino-stau), which facilitate the simultaneous satisfaction of all the above requirements. In both cases above, the neutralino abundance can essentially decrease for a wino or higgsino like LSP creating regions of parameter space with additional neutralino-chargino and/or heavier neutralino coannihilations. The neutralino-sbottom mass proximity significantly ameliorates the detectability of LSP

Minimal unitary representation of D(2,1;λ) and its SU(2) deformations and d=1, N=4 superconformal models

International Nuclear Information System (INIS)

Govil, Karan; Gunaydin, Murat

2013-01-01

Quantization of the geometric quasiconformal realizations of noncompact groups and supergroups leads directly to their minimal unitary representations (minreps). Using quasiconformal methods massless unitary supermultiplets of superconformal groups SU(2,2|N) and OSp(8 ⁎ |2n) in four and six dimensions were constructed as minreps and their U(1) and SU(2) deformations, respectively. In this paper we extend these results to SU(2) deformations of the minrep of N=4 superconformal algebra D(2,1;λ) in one dimension. We find that SU(2) deformations can be achieved using n pair of bosons and m pairs of fermions simultaneously. The generators of deformed minimal representations of D(2,1;λ) commute with the generators of a dual superalgebra OSp(2n ⁎ |2m) realized in terms of these bosons and fermions. We show that there exists a precise mapping between symmetry generators of N=4 superconformal models in harmonic superspace studied recently and minimal unitary supermultiplets of D(2,1;λ) deformed by a pair of bosons. This can be understood as a particular case of a general mapping between the spectra of quantum mechanical quaternionic Kähler sigma models with eight super symmetries and minreps of their isometry groups that descends from the precise mapping established between the 4d, N=2 sigma models coupled to supergravity and minreps of their isometry groups.

On the branching of the quasinormal resonances of near-extremal Kerr black holes

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar, E-mail: shaharhod@gmail.com [The Ruppin Academic Center, 40250, Emeq Hefer (Israel); The Hadassah Institute, 91010, Jerusalem (Israel)

2015-11-02

It has recently been shown by Yang et al. (Phys Rev D 87:041502(R), 2013a; Phys Rev D 88:044047, 2013b) that rotating Kerr black holes are characterized by two distinct sets of quasinormal resonances. These two families of quasinormal resonances display qualitatively different asymptotic behaviors in the extremal (a/M→1) black-hole limit: the zero-damping modes are characterized by relaxation times which tend to infinity in the extremal black-hole limit (Iω→0 as a/M→1), whereas the damped modes (DMs) are characterized by non-zero damping rates (Iω→ finite-values as a/M→1). In this paper we refute the claim made by Yang et al. that co-rotating DMs of near-extremal black holes are restricted to the limited range 0≤μ≲μ{sub c}≈0.74, where μ≡m/l is the dimensionless ratio between the azimuthal harmonic index m and the spheroidal harmonic index l of the perturbation mode. In particular, we use an analytical formula originally derived by Detweiler in order to prove the existence of DMs (damped quasinormal resonances which are characterized by finiteIω values in the a/M→1 limit) of near-extremal black holes in the μ>μ{sub c} regime, the regime which was claimed by Yang et al. not to contain DMs. We show that these co-rotating DMs (in the regime μ>μ{sub c}) are expected to characterize the resonance spectra of rapidly rotating (near-extremal) black holes with a/M≳1-10{sup -9}.

Equivalence of quantum states under local unitary transformations

International Nuclear Information System (INIS)

Fei Shaoming; Jing Naihuan

2005-01-01

In terms of the analysis of fixed point subgroup and tensor decomposability of certain matrices, we study the equivalence of quantum bipartite mixed states under local unitary transformations. For non-degenerate case an operational criterion for the equivalence of two such mixed bipartite states under local unitary transformations is presented

Non-minimal Maxwell-Chern-Simons theory and the composite Fermion model

International Nuclear Information System (INIS)

Paschoal, Ricardo C.; Helayel Neto, Jose A.

2003-01-01

The magnetic field redefinition in Jain's composite fermion model for the fractional quantum Hall effect is shown to be effective described by a mean-field approximation of a model containing a Maxwell-Chern-Simons gauge field nominally coupled to matter. Also an explicit non-relativistic limit of the non-minimal (2+1) D Dirac's equation is derived. (author)

Fermion cluster algorithms

International Nuclear Information System (INIS)

Chandrasekharan, Shailesh

2000-01-01

Cluster algorithms have been recently used to eliminate sign problems that plague Monte-Carlo methods in a variety of systems. In particular such algorithms can also be used to solve sign problems associated with the permutation of fermion world lines. This solution leads to the possibility of designing fermion cluster algorithms in certain cases. Using the example of free non-relativistic fermions we discuss the ideas underlying the algorithm

Non-perturbative renormalization of static-light four-fermion operators in quenched lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Palombi, F. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Papinutto, M.; Pena, C. [CERN, Geneva (Switzerland). Physics Dept., Theory Div.; Wittig, H. [Mainz Univ. (Germany). Inst. fuer Kernphysik

2007-06-15

We perform a non-perturbative study of the scale-dependent renormalization factors of a multiplicatively renormalizable basis of {delta}B=2 parity-odd four-fermion operators in quenched lattice QCD. Heavy quarks are treated in the static approximation with various lattice discretizations of the static action. Light quarks are described by nonperturbatively O(a) improved Wilson-type fermions. The renormalization group running is computed for a family of Schroedinger functional (SF) schemes through finite volume techniques in the continuum limit. We compute non-perturbatively the relation between the renormalization group invariant operators and their counterparts renormalized in the SF at a low energy scale. Furthermore, we provide non-perturbative estimates for the matching between the lattice regularized theory and all the SF schemes considered. (orig.)

Quasinormal Modes of a Quantum-Corrected Schwarzschild Black ...

Indian Academy of Sciences (India)

Chunyan Wang

2017-11-27

Nov 27, 2017 ... Abstract. In this work, we investigate the electromagnetic perturbation around a quantum-corrected. Schwarzschild black hole. The complex frequencies of the quasinormal modes are evaluated by the third- order WKB approximation. The numerical results obtained showed that the complex frequencies ...

Highly imbalanced fermion-fermion mixtures in one dimension

International Nuclear Information System (INIS)

Recher, Christian

2013-01-01

In the framework of exactly solvable quantum many-body systems we study models of interacting spin one-half Fermions in one dimension. The first part deals with systems of spin one-half Fermions which interact via repulsive contact interaction. A reformulation of the Bethe-Ansatz solvable many-body wave function is presented. This simplifies considerably the calculations for the highly imbalanced case, where very few particles of one species (minority Fermions) are present. For the other particle species (majority Fermions) the thermodynamic limit is taken. We assume the majority Fermions to be in the ground state such that their non-interacting momentum distribution is a Fermi-sea. Upon this we consider excitations where the particles of the minority species may occupy an arbitrary state within the Fermi-sea. In the case of only a single minority Fermion, the many-body wave function can be expressed as a determinant. This allows us to derive exact thermodynamic expressions for several expectation values as well as for the density-density correlation function. Moreover it is possible to find closed expressions for the single particle Green's function. All of the above mentioned quantities show a non-trivial dependence on the minority particle's momentum. In particular the Green's function in the Tonks-Girardeau regime of hardcore interaction is shown to undergo a transition from the one of impenetrable Bosons to that of free Fermions as the extra particle's momentum varies from the core to the edge of the Fermi-sea. This transition becomes manifest in an algebraic asymptotic decay of the Green's function. If two minority Fermions are present, the many-body wave function turns out to be more complicated. Nevertheless it is possible to derive exact expressions for the two and the three particle density-density correlation functions. Furthermore we calculate the system's total energy and based on that, identify terms which have a natural

On the branching of the quasinormal resonances of near-extremal Kerr black holes

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Institute, Jerusalem (Israel)

2015-11-15

It has recently been shown by Yang et al. (Phys Rev D 87:041502(R), 2013a; Phys Rev D 88:044047, 2013b) that rotating Kerr black holes are characterized by two distinct sets of quasinormal resonances. These two families of quasinormal resonances display qualitatively different asymptotic behaviors in the extremal (a/M → 1) black-hole limit: the zero-damping modes are characterized by relaxation times which tend to infinity in the extremal black-hole limit (Iω → 0 as a/M @→ 1), whereas the damped modes (DMs) are characterized by non-zero damping rates (Iω @→ finite-values as a/M @→ 1). In this paper we refute the claim made by Yang et al. that co-rotating DMs of near-extremal black holes are restricted to the limited range 0 ≤ μ quasinormal resonances which are characterized by finite Iω values in the a/M @→ 1 limit) of near-extremal black holes in the μ > μ{sub c} regime, the regime which was claimed by Yang et al. not to contain DMs. We show that these co-rotating DMs (in the regime μ > μ{sub c}) are expected to characterize the resonance spectra of rapidly rotating (near-extremal) black holes with a/M >or similar 1 - 10{sup -9}. (orig.)

Quench of non-Markovian coherence in the deep sub-Ohmic spin–boson model: A unitary equilibration scheme

International Nuclear Information System (INIS)

Yao, Yao

2015-01-01

The deep sub-Ohmic spin–boson model shows a longstanding non-Markovian coherence at low temperature. Motivating to quench this robust coherence, the thermal effect is unitarily incorporated into the time evolution of the model, which is calculated by the adaptive time-dependent density matrix renormalization group algorithm combined with the orthogonal polynomials theory. Via introducing a unitary heating operator to the bosonic bath, the bath is heated up so that a majority portion of the bosonic excited states is occupied. It is found in this situation the coherence of the spin is quickly quenched even in the coherent regime, in which the non-Markovian feature dominates. With this finding we come up with a novel way to implement the unitary equilibration, the essential term of the eigenstate-thermalization hypothesis, through a short-time evolution of the model

The universal sound velocity formula for the strongly interacting unitary Fermi gas

International Nuclear Information System (INIS)

Liu Ke; Chen Ji-Sheng

2011-01-01

Due to the scale invariance, the thermodynamic laws of strongly interacting limit unitary Fermi gas can be similar to those of non-interacting ideal gas. For example, the virial theorem between pressure and energy density of the ideal gas P = 2E/3V is still satisfied by the unitary Fermi gas. This paper analyses the sound velocity of unitary Fermi gases with the quasi-linear approximation. For comparison, the sound velocities for the ideal Boltzmann, Bose and Fermi gas are also given. Quite interestingly, the sound velocity formula for the ideal non-interacting gas is found to be satisfied by the unitary Fermi gas in different temperature regions. (general)

Unitary field theories

International Nuclear Information System (INIS)

Bergmann, P.G.

1980-01-01

A problem of construction of the unitary field theory is discussed. The preconditions of the theory are briefly described. The main attention is paid to the geometrical interpretation of physical fields. The meaning of the conceptions of diversity and exfoliation is elucidated. Two unitary field theories are described: the Weyl conformic geometry and Calitzy five-dimensioned theory. It is proposed to consider supersymmetrical theories as a new approach to the problem of a unitary field theory. It is noted that the supergravitational theories are really unitary theories, since the fields figuring there do not assume invariant expansion

Regularized quasinormal modes for plasmonic resonators and open cavities

Science.gov (United States)

Kamandar Dezfouli, Mohsen; Hughes, Stephen

2018-03-01

Optical mode theory and analysis of open cavities and plasmonic particles is an essential component of optical resonator physics, offering considerable insight and efficiency for connecting to classical and quantum optical properties such as the Purcell effect. However, obtaining the dissipative modes in normalized form for arbitrarily shaped open-cavity systems is notoriously difficult, often involving complex spatial integrations, even after performing the necessary full space solutions to Maxwell's equations. The formal solutions are termed quasinormal modes, which are known to diverge in space, and additional techniques are frequently required to obtain more accurate field representations in the far field. In this work, we introduce a finite-difference time-domain technique that can be used to obtain normalized quasinormal modes using a simple dipole-excitation source, and an inverse Green function technique, in real frequency space, without having to perform any spatial integrations. Moreover, we show how these modes are naturally regularized to ensure the correct field decay behavior in the far field, and thus can be used at any position within and outside the resonator. We term these modes "regularized quasinormal modes" and show the reliability and generality of the theory by studying the generalized Purcell factor of dipole emitters near metallic nanoresonators, hybrid devices with metal nanoparticles coupled to dielectric waveguides, as well as coupled cavity-waveguides in photonic crystals slabs. We also directly compare our results with full-dipole simulations of Maxwell's equations without any approximations, and show excellent agreement.

Unitary Root Music and Unitary Music with Real-Valued Rank Revealing Triangular Factorization

Science.gov (United States)

2010-06-01

AFRL-RY-WP-TP-2010-1213 UNITARY ROOT MUSIC AND UNITARY MUSIC WITH REAL-VALUED RANK REVEALING TRIANGULAR FACTORIZATION (Postprint) Nizar...DATES COVERED (From - To) June 2010 Journal Article Postprint 08 September 2006 – 31 August 2009 4. TITLE AND SUBTITLE UNITARY ROOT MUSIC AND...UNITARY MUSIC WITH REAL-VALUED RANK REVEALING TRIANGULAR FACTORIZATION (Postprint) 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA8650-05-D-1912-0007 5c

Quasinormal modes and classical wave propagation in analogue black holes

International Nuclear Information System (INIS)

Berti, Emanuele; Cardoso, Vitor; Lemos, Jose P.S.

2004-01-01

Many properties of black holes can be studied using acoustic analogues in the laboratory through the propagation of sound waves. We investigate in detail sound wave propagation in a rotating acoustic (2+1)-dimensional black hole, which corresponds to the 'draining bathtub' fluid flow. We compute the quasinormal mode frequencies of this system and discuss late-time power-law tails. Because of the presence of an ergoregion, waves in a rotating acoustic black hole can be superradiantly amplified. We also compute superradiant reflection coefficients and instability time scales for the acoustic black hole bomb, the equivalent of the Press-Teukolsky black hole bomb. Finally we discuss quasinormal modes and late-time tails in a nonrotating canonical acoustic black hole, corresponding to an incompressible, spherically symmetric (3+1)-dimensional fluid flow

Random unitary operations and quantum Darwinism

International Nuclear Information System (INIS)

Balaneskovic, Nenad

2016-01-01

We study the behavior of Quantum Darwinism (Zurek, Nature Physics 5, 181-188 (2009)) within the iterative, random unitary operations qubit-model of pure decoherence (Novotn'y et al, New Jour. Phys. 13, 053052 (2011)). We conclude that Quantum Darwinism, which describes the quantum mechanical evolution of an open system from the point of view of its environment, is not a generic phenomenon, but depends on the specific form of initial states and on the type of system-environment interactions. Furthermore, we show that within the random unitary model the concept of Quantum Darwinism enables one to explicitly construct and specify artificial initial states of environment that allow to store information about an open system of interest and its pointer-basis with maximal efficiency. Furthermore, we investigate the behavior of Quantum Darwinism after introducing dissipation into the iterative random unitary qubit model with pure decoherence in accord with V. Scarani et al (Phys. Rev. Lett. 88, 097905 (2002)) and reconstruct the corresponding dissipative attractor space. We conclude that in Zurek's qubit model Quantum Darwinism depends on the order in which pure decoherence and dissipation act upon an initial state of the entire system. We show explicitly that introducing dissipation into the random unitary evolution model in general suppresses Quantum Darwinism (regardless of the order in which decoherence and dissipation are applied) for all positive non-zero values of the dissipation strength parameter, even for those initial state configurations which, in Zurek's qubit model and in the random unitary model with pure decoherence, would lead to Quantum Darwinism. Finally, we discuss what happens with Quantum Darwinism after introducing into the iterative random unitary qubit model with pure decoherence (asymmetric) dissipation and dephasing, again in accord with V. Scarani et al (Phys. Rev. Lett. 88, 097905 (2002)), and reconstruct the corresponding

About the unitary discretizations of Heisenberg equations of motion

International Nuclear Information System (INIS)

Vazquez, L.

1986-01-01

In a recent paper Bender et al. (1985) have used a unitary discretization of Heisenberg equations for a one-dimensional quantum system in order to obtain information about the spectrum of the underlying continuum theory. The method consists in comparing the matrix elements between adjacent Fock states of the operators and at two steps. At the same time a very simple variational approach must be made. The purpose of this paper is to show that with unitary schemes, accurate either to order τ or τ 2 , we obtain the same spectrum results in the framework of the above method. On the other hand the same eigenvalues are obtained with a non-unitary scheme (Section II). In Section III we discuss the construction of the Hamiltonian associated to the unitary discretizations. (orig.)

Mode entanglement of Gaussian fermionic states

Science.gov (United States)

Spee, C.; Schwaiger, K.; Giedke, G.; Kraus, B.

2018-04-01

We investigate the entanglement of n -mode n -partite Gaussian fermionic states (GFS). First, we identify a reasonable definition of separability for GFS and derive a standard form for mixed states, to which any state can be mapped via Gaussian local unitaries (GLU). As the standard form is unique, two GFS are equivalent under GLU if and only if their standard forms coincide. Then, we investigate the important class of local operations assisted by classical communication (LOCC). These are central in entanglement theory as they allow one to partially order the entanglement contained in states. We show, however, that there are no nontrivial Gaussian LOCC (GLOCC) among pure n -partite (fully entangled) states. That is, any such GLOCC transformation can also be accomplished via GLU. To obtain further insight into the entanglement properties of such GFS, we investigate the richer class of Gaussian stochastic local operations assisted by classical communication (SLOCC). We characterize Gaussian SLOCC classes of pure n -mode n -partite states and derive them explicitly for few-mode states. Furthermore, we consider certain fermionic LOCC and show how to identify the maximally entangled set of pure n -mode n -partite GFS, i.e., the minimal set of states having the property that any other state can be obtained from one state inside this set via fermionic LOCC. We generalize these findings also to the pure m -mode n -partite (for m >n ) case.

Joule-Thomson Coefficient for Strongly Interacting Unitary Fermi Gas

International Nuclear Information System (INIS)

Liao Kai; Chen Jisheng; Li Chao

2010-01-01

The Joule-Thomson effect reflects the interaction among constituent particles of macroscopic system. For classical ideal gas, the corresponding Joule-Thomson coefficient is vanishing while it is non-zero for ideal quantum gas due to the quantum degeneracy. In recent years, much attention is paid to the unitary Fermi gas with infinite two-body scattering length. According to universal analysis, the thermodynamical law of unitary Fermi gas is similar to that of non-interacting ideal gas, which can be explored by the virial theorem P = 2E/3V. Based on previous works, we further study the unitary Fermi gas properties. The effective chemical potential is introduced to characterize the nonlinear levels crossing effects in a strongly interacting medium. The changing behavior of the rescaled Joule-Thomson coefficient according to temperature manifests a quite different behavior from that for ideal Fermi gas. (general)

A detailed analytic study of the asymptotic quasinormal modes of Schwarzschild-anti de Sitter black holes

International Nuclear Information System (INIS)

Daghigh, Ramin G; Green, Michael D

2009-01-01

We analyze analytically the asymptotic regions of the quasinormal mode frequency spectra with infinitely large overtone numbers for D-dimensional Schwarzschild black holes in anti de Sitter spacetimes. In this limit, we confirm the analytic results obtained previously in the literature using different methods. In addition, we show that in certain spacetime dimensions these techniques imply the existence of other regions of the asymptotic quasinormal mode frequency spectrum which have not previously appeared in the literature. For large black holes, some of these modes have a damping rate of 1.2T H , where T H is the Hawking temperature. This is less than the damping rate of the lowest overtone quasinormal mode calculated by other authors. It is not completely clear whether these modes actually exist or are an artifact of an unknown flaw in the analytic techniques being used. We discuss the possibility of the existence of these modes and explore some of the consequences. We also examine the possible connection between the asymptotic quasinormal modes of Schwarzschild-anti de Sitter black holes and the quantum level spacing of their horizon area spectrum.

On Quasinormal Modes for Scalar Perturbations of Static Spherically Symmetric Black Holes in Nash Embedding Framework

Directory of Open Access Journals (Sweden)

Sergio C. Ulhoa

2017-01-01

Full Text Available In this paper we investigate scalar perturbations of black holes embedded in a five-dimensional bulk space. The quasinormal frequencies of such black holes are calculated using the third order of Wentzel, Kramers, and Brillouin (WKB approximation for scalar perturbations. The high overtones of quasinormal modes indicate a resonant-like set of black holes suggesting a serious constraint of embedding models in five dimensions.

A quantum theory of the self-energy of non-relativistic fermions and of the Coulomb-Yukawa force acting between them

International Nuclear Information System (INIS)

Ernst, V.

1978-01-01

The idea of the systematic Weisskopf-Wigner approximation as used sporadically in atomic physics and quantum optics, is extended here to the interaction of a field of non-relativistic fermions with a field of relativistic bosons. It is shown that the usual (non-existing) interaction Hamiltonian of this system can be written as a sum of a countable number of self-adjoint and bounded partial Hamiltonians. The system of these Hamiltonians defines the order hierarchy of the present approximation scheme. To demonstrate its physical utility it is shown that in a certain order it provides satisfactory quantum theory of the 'self-energy' of the fermions under discussion. This is defined as the binding energy of bosons bound to the fermions and building up the latter's 'individual Coulomb or Yukawa fields' in the sense of expectation values of the corresponding field operator. In states of more than one fermion the bound photons act as a mediating agent between the fermions; this mechanism closely resembles the Coulomb or Yukawa 'forces' used in conventional non-relativistic quantum mechanics. (author)

Non-unitary neutrino propagation from neutrino decay

Energy Technology Data Exchange (ETDEWEB)

Berryman, Jeffrey M., E-mail: jeffreyberryman2012@u.northwestern.edu [Northwestern University, Department of Physics & Astronomy, 2145 Sheridan Road, Evanston, IL 60208 (United States); Gouvêa, André de; Hernández, Daniel [Northwestern University, Department of Physics & Astronomy, 2145 Sheridan Road, Evanston, IL 60208 (United States); Oliveira, Roberto L.N. [Northwestern University, Department of Physics & Astronomy, 2145 Sheridan Road, Evanston, IL 60208 (United States); Instituto de Física Gleb Wataghin Universidade Estadual de Campinas, UNICAMP 13083-970, Campinas, São Paulo (Brazil)

2015-03-06

Neutrino propagation in space-time is not constrained to be unitary if very light states – lighter than the active neutrinos – exist into which neutrinos may decay. If this is the case, neutrino flavor-change is governed by a handful of extra mixing and “oscillation” parameters, including new sources of CP-invariance violation. We compute the transition probabilities in the two- and three-flavor scenarios and discuss the different phenomenological consequences of the new physics. These are qualitatively different from other sources of unitarity violation discussed in the literature.

Non-unitary neutrino propagation from neutrino decay

International Nuclear Information System (INIS)

Berryman, Jeffrey M.; Gouvêa, André de; Hernández, Daniel; Oliveira, Roberto L.N.

2015-01-01

Neutrino propagation in space-time is not constrained to be unitary if very light states – lighter than the active neutrinos – exist into which neutrinos may decay. If this is the case, neutrino flavor-change is governed by a handful of extra mixing and “oscillation” parameters, including new sources of CP-invariance violation. We compute the transition probabilities in the two- and three-flavor scenarios and discuss the different phenomenological consequences of the new physics. These are qualitatively different from other sources of unitarity violation discussed in the literature

2-fermion and 4-fermion production at LEP2

CERN Document Server

van Vulpen, Ivo B

2000-01-01

We present the measurements on 2-fermion and 4-fermion production in e + e - collisions at centre-of-mass energies ranging from 192 to 202 Ge V as collected by the 4 LEP experiments in 1999. For processes with 2-fermions in the final state we present both production cross sections and asymmetries for event samples at low and high effective centre-of-mass energies, where the latter process is sensitive to possible contributions from various non-SM physics, like contact interactions or Z' exchange, and can therefore be used to set limits on parameters in those models. We also report on the measured cross sections for a subset of processes leading to 4 fermions in the final state: pair production of heavy vector bosons w+w- (NC03) and ZZ (NC02) followed by single-W production. A measurement of the leptonic branching ratio of the W-boson is used to extract information on IV c• I

Leptonic unitary triangles and boomerangs

International Nuclear Information System (INIS)

Dueck, Alexander; Rodejohann, Werner; Petcov, Serguey T.

2010-01-01

We review the idea of leptonic unitary triangles and extend the concept of the recently proposed unitary boomerangs to the lepton sector. Using a convenient parametrization of the lepton mixing, we provide approximate expressions for the side lengths and the angles of the six different triangles and give examples of leptonic unitary boomerangs. Possible applications of the leptonic unitary boomerangs are also briefly discussed.

Quasinormal modes of black holes in Lovelock gravity

Science.gov (United States)

Yoshida, Daiske; Soda, Jiro

2016-02-01

We study quasinormal modes of black holes in Lovelock gravity. We formulate the WKB method adapted to Lovelock gravity for the calculation of quasinormal frequencies (QNFs). As a demonstration, we calculate various QNFs of Lovelock black holes in seven and eight dimensions. We find that the QNFs show remarkable features depending on the coefficients of the Lovelock terms, the species of perturbations, and spacetime dimensions. In the case of the scalar field, when we increase the coefficient of the third order Lovelock term, the real part of QNFs increases, but the decay rate becomes small irrespective of the mass of the black hole. For small black holes, the decay rate ceases to depend on the Gauss-Bonnet term. In the case of tensor type perturbations of the metric field, the tendency of the real part of QNFs is opposite to that of the scalar field. The QNFs of vector type perturbations of the metric show no particular behavior. The behavior of QNFs of the scalar type perturbations of the metric field is similar to the vector type. However, available data are rather sparse, which indicates that the WKB method is not applicable to many models for this sector.

Gauge invariance and fermion mass dimensions

International Nuclear Information System (INIS)

Elias, V.

1979-05-01

Renormalization-group equation fermion mass dimensions are shown to be gauge dependent in gauge theories possessing non-vector couplings of gauge bosons to fermions. However, the ratios of running fermion masses are explicitly shown to be gauge invariant in the SU(5) and SU(2) x U(1) examples of such theories. (author)

Fermion masses through four-fermion condensates

Energy Technology Data Exchange (ETDEWEB)

Ayyar, Venkitesh [Department of Physics, Duke University,Science Drive, Durham, NC 27708 (United States); Chandrasekharan, Shailesh [Department of Physics, Duke University,Science Drive, Durham, NC 27708 (United States); Center for High Energy Physics, Indian Institute of Science,C.V. Raman Avenue, Bangalore, 560012 (India)

2016-10-12

Fermion masses can be generated through four-fermion condensates when symmetries prevent fermion bilinear condensates from forming. This less explored mechanism of fermion mass generation is responsible for making four reduced staggered lattice fermions massive at strong couplings in a lattice model with a local four-fermion coupling. The model has a massless fermion phase at weak couplings and a massive fermion phase at strong couplings. In particular there is no spontaneous symmetry breaking of any lattice symmetries in both these phases. Recently it was discovered that in three space-time dimensions there is a direct second order phase transition between the two phases. Here we study the same model in four space-time dimensions and find results consistent with the existence of a narrow intermediate phase with fermion bilinear condensates, that separates the two asymptotic phases by continuous phase transitions.

Fermions and vortex solutions in Abelian and non-Abelian gauge theories

International Nuclear Information System (INIS)

de Vega, H.J.

1978-01-01

The interaction of fermions with an extended vortex solution of the Higgs model is investigated. It is found that this interaction has long-range inverse-square tail. It is caused by the coupling of the fermion angular momentum with the vortex gauge field itself. The fermion-vortex bound states present at the threshold and the fermion-vortex scattering are studied. The scattering phase shifts and the Jost functions are obtained for large and small fermion momenta as well as the low-energy cross section which diverges at zero momentum. The quantum field theory in the one-vortex sectors is developed. It is found that, in the presence of fermions, a vortex with an even (odd) number of flux quanta has a half-integer (integer) fermionic number. It follows that a two-quantum vortex is stable. Finally, the stable vortex solution of an SU(2) Higgs model is investigated. The appropriate ansatz for the field is given and radial equations are discussed. It is shown that the interaction of a vortex with any nonsinglet particle has a long-range inverse-square tail

Lattice fermions at non-zero temperature and chemical potential

International Nuclear Information System (INIS)

Bender, I.

1993-01-01

We study the free fermion gas at finite temperature and chemical potential in the lattice regularized version proposed by Hasenfratz and Karsch. Special emphasis is placed on the identification of the particle and antiparticle contributions to the partition function. In the case of naive fermions we show that the partition function no longer separates into particle-antiparticle contributions in the way familiar from the continuum formulation. The use of Wilson fermions, on the other hand, eliminates this unpleasant feature, and leads, after subtracting the vacuum contributions, to the familiar expressions for the average energy and charge densities. (orig.)

On the unitary transformation between non-quasifree and quasifree state spaces and its application to quantum field theory on curved spacetimes

International Nuclear Information System (INIS)

Gottschalk, Hanno; Hack, Thomas-Paul

2009-12-01

Using *-calculus on the dual of the Borchers-Uhlmann algebra endowed with a combinatorial co-product, we develop a method to calculate a unitary transformation relating the GNS representations of a non-quasifree and a quasifree state of the free hermitian scalar field. The motivation for such an analysis and a further result is the fact that a unitary transformation of this kind arises naturally in scattering theory on non-stationary backgrounds. Indeed, employing the perturbation theory of the Yang-Feldman equations with a free CCR field in a quasifree state as an initial condition and making use of extended Feynman graphs, we are able to calculate the Wightman functions of the interacting and outgoing fields in a φ p -theory on arbitrary curved spacetimes. A further examination then reveals two major features of the aforementioned theory: firstly, the interacting Wightman functions fulfil the basic axioms of hermiticity, invariance, spectrality (on stationary spacetimes), perturbative positivity, and locality. Secondly, the outgoing field is free and fulfils the CCR, but is in general not in a quasifree state in the case of a non-stationary spacetime. In order to obtain a sensible particle picture for the outgoing field and, hence, a description of the scattering process in terms of particles (in asymptotically flat spacetimes), it is thus necessary to compute a unitary transformation of the abovementioned type. (orig.)

On the unitary transformation between non-quasifree and quasifree state spaces and its application to quantum field theory on curved spacetimes

Energy Technology Data Exchange (ETDEWEB)

Gottschalk, Hanno [Bonn Univ. (Germany). Inst. fuer Angewandte Mathematik; Hack, Thomas-Paul [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik

2009-12-15

Using *-calculus on the dual of the Borchers-Uhlmann algebra endowed with a combinatorial co-product, we develop a method to calculate a unitary transformation relating the GNS representations of a non-quasifree and a quasifree state of the free hermitian scalar field. The motivation for such an analysis and a further result is the fact that a unitary transformation of this kind arises naturally in scattering theory on non-stationary backgrounds. Indeed, employing the perturbation theory of the Yang-Feldman equations with a free CCR field in a quasifree state as an initial condition and making use of extended Feynman graphs, we are able to calculate the Wightman functions of the interacting and outgoing fields in a {phi}{sup p}-theory on arbitrary curved spacetimes. A further examination then reveals two major features of the aforementioned theory: firstly, the interacting Wightman functions fulfil the basic axioms of hermiticity, invariance, spectrality (on stationary spacetimes), perturbative positivity, and locality. Secondly, the outgoing field is free and fulfils the CCR, but is in general not in a quasifree state in the case of a non-stationary spacetime. In order to obtain a sensible particle picture for the outgoing field and, hence, a description of the scattering process in terms of particles (in asymptotically flat spacetimes), it is thus necessary to compute a unitary transformation of the abovementioned type. (orig.)

Classification of delocalization power of global unitary operations in terms of LOCC one-piece relocalization

Directory of Open Access Journals (Sweden)

Akihito Soeda

2010-06-01

Full Text Available We study how two pieces of localized quantum information can be delocalized across a composite Hilbert space when a global unitary operation is applied. We classify the delocalization power of global unitary operations on quantum information by investigating the possibility of relocalizing one piece of the quantum information without using any global quantum resource. We show that one-piece relocalization is possible if and only if the global unitary operation is local unitary equivalent of a controlled-unitary operation. The delocalization power turns out to reveal different aspect of the non-local properties of global unitary operations characterized by their entangling power.

Duality and topology

Science.gov (United States)

Sacramento, P. D.; Vieira, V. R.

2018-04-01

Mappings between models may be obtained by unitary transformations with preservation of the spectra but in general a change in the states. Non-canonical transformations in general also change the statistics of the operators involved. In these cases one may expect a change of topological properties as a consequence of the mapping. Here we consider some dualities resulting from mappings, by systematically using a Majorana fermion representation of spin and fermionic problems. We focus on the change of topological invariants that results from unitary transformations taking as examples the mapping between a spin system and a topological superconductor, and between different fermionic systems.

Quantum return probability of a system of N non-interacting lattice fermions

Science.gov (United States)

Krapivsky, P. L.; Luck, J. M.; Mallick, K.

2018-02-01

We consider N non-interacting fermions performing continuous-time quantum walks on a one-dimensional lattice. The system is launched from a most compact configuration where the fermions occupy neighboring sites. We calculate exactly the quantum return probability (sometimes referred to as the Loschmidt echo) of observing the very same compact state at a later time t. Remarkably, this probability depends on the parity of the fermion number—it decays as a power of time for even N, while for odd N it exhibits periodic oscillations modulated by a decaying power law. The exponent also slightly depends on the parity of N, and is roughly twice smaller than what it would be in the continuum limit. We also consider the same problem, and obtain similar results, in the presence of an impenetrable wall at the origin constraining the particles to remain on the positive half-line. We derive closed-form expressions for the amplitudes of the power-law decay of the return probability in all cases. The key point in the derivation is the use of Mehta integrals, which are limiting cases of the Selberg integral.

Fermion unification model based on the intrinsic SU(8 symmetry of a generalized Dirac equation

Directory of Open Access Journals (Sweden)

Eckart eMarsch

2015-10-01

Full Text Available A natural generalization of the original Dirac spinor into a multi-component spinor is achieved, which corresponds to the single lepton and the three quarks of the first family of the standard model of elementary particle physics. Different fermions result from similarity transformations of the Dirac equation, but apparently there can be no more fermions according to the maximal multiplicity revealed in this study. Rotations in the fermion state space are achieved by the unitary generators of the U(1 and the SU(3 groups, corresponding to quantum electrodynamics (QED based on electric charge and chromodynamics (QCD based on colour charge. In addition to hypercharge the dual degree of freedom of hyperspin emerges, which occurs due to the duplicity implied by the two related (Weyl and Dirac representations of the Dirac equation. This yields the SU(2 symmetry of the weak interaction, which can be married to U(1 to generate the unified electroweak interaction as in the standard model. Therefore, the symmetry group encompassing all the three groups mentioned above is SU(8, which can accommodate and unify the observed eight basic stable fermions.

Stretched horizons, quasiparticles, and quasinormal modes

International Nuclear Information System (INIS)

Iizuka, Norihiro; Kabat, Daniel; Lifschytz, Gilad; Lowe, David A.

2003-01-01

We propose that stretched horizons can be described in terms of a gas of noninteracting quasiparticles. The quasiparticles are unstable, with a lifetime set by the imaginary part of the lowest quasinormal mode frequency. If the horizon arises from an AdS-CFT style duality the quasiparticles are also the effective low-energy degrees of freedom of the finite-temperature CFT. We analyze a large class of models including Schwarzschild black holes, nonextremal Dp-branes, the rotating BTZ black hole and de Sitter space, and we comment on degenerate horizons. The quasiparticle description makes manifest the relationship between entropy and area

Unitary or Non-Unitary Nature of Working Memory? Evidence from Its Relation to General Fluid and Crystallized Intelligence

Science.gov (United States)

Dang, Cai-Ping; Braeken, Johan; Ferrer, Emilio; Liu, Chang

2012-01-01

This study explored the controversy surrounding working memory: whether it is a unitary system providing general purpose resources or a more differentiated system with domain-specific sub-components. A total of 348 participants completed a set of 6 working memory tasks that systematically varied in storage target contents and type of information…

Non-perturbative improvement of stout-smeared three flavour clover fermions

Energy Technology Data Exchange (ETDEWEB)

Cundy, N.; Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (GB). School of Physics and Astronomy] (and others)

2009-01-15

We discuss a 3-flavour lattice QCD action with clover improvement in which the fermion matrix has single level stout smearing for the hopping terms together with unsmeared links for the clover term. With the (tree-level) Symanzik improved gluon action this constitutes the Stout Link Non-perturbative Clover or SLiNC action. To cancel O(a) terms the clover term coefficient has to be tuned. We present here results of a non-perturbative determination of this coefficient using the Schroedinger functional and as a by-product a determination of the critical hopping parameter. Comparisons of the results are made with lowest order perturbation theory. (orig.)

Quasinormal modes of Gauss-Bonnet-AdS black holes: towards holographic description of finite coupling

Science.gov (United States)

Konoplya, R. A.; Zhidenko, A.

2017-09-01

Here we shall show that there is no other instability for the Einstein-Gauss-Bonnet-anti-de Sitter (AdS) black holes, than the eikonal one and consider the features of the quasinormal spectrum in the stability sector in detail. The obtained quasinormal spectrum consists from the two essentially different types of modes: perturbative and non-perturbative in the Gauss-Bonnet coupling α. The sound and hydrodynamic modes of the perturbative branch can be expressed through their Schwazrschild-AdS limits by adding a linear in α correction to the damping rates: ω≈Re ω SAdS -Im ω SAdS(1- α·(( D+1)( D-4) /2 R 2)) i, where R is the AdS radius. The non-perturbative branch of modes consists of purely imaginary modes, whose damping rates unboundedly increase when α goes to zero. When the black hole radius is much larger than the anti-de Sitter radius R, the regime of the black hole with planar horizon (black brane) is reproduced. If the Gauss-Bonnet coupling α (or used in holography λGB) is not small enough, then the black holes and branes suffer from the instability, so that the holographic interpretation of perturbation of such black holes becomes questionable, as, for example, the claimed viscosity bound violation in the higher derivative gravity. For example, D = 5 black brane is unstable at |λGB| > 1 /8 and has anomalously large relaxation time when approaching the threshold of instability.

Stability analysis and quasinormal modes of Reissner–Nordstrøm ...

Indian Academy of Sciences (India)

2016-06-09

Jun 9, 2016 ... They also determine important features of the space-time and give important information on the background geometry. The Lyapunov exponent (λ) has been used to probe the instability of circular null geodesics and in terms of the quasinormal modes (QNMs) for spherically symmetric space-time of arbitrary ...

Quasi-normal modes of extremal BTZ black holes in TMG

Science.gov (United States)

Afshar, Hamid R.; Alishahiha, Mohsen; Mosaffa, Amir E.

2010-08-01

We study the spectrum of tensor perturbations on extremal BTZ black holes in topologically massive gravity for arbitrary values of the coefficient of the Chern-Simons term, μ. Imposing proper boundary conditions at the boundary of the space and at the horizon, we find that the spectrum contains quasi-normal modes.

Fermion systems in discrete space-time

International Nuclear Information System (INIS)

Finster, Felix

2007-01-01

Fermion systems in discrete space-time are introduced as a model for physics on the Planck scale. We set up a variational principle which describes a non-local interaction of all fermions. This variational principle is symmetric under permutations of the discrete space-time points. We explain how for minimizers of the variational principle, the fermions spontaneously break this permutation symmetry and induce on space-time a discrete causal structure

Fermion systems in discrete space-time

Energy Technology Data Exchange (ETDEWEB)

Finster, Felix [NWF I - Mathematik, Universitaet Regensburg, 93040 Regensburg (Germany)

2007-05-15

Fermion systems in discrete space-time are introduced as a model for physics on the Planck scale. We set up a variational principle which describes a non-local interaction of all fermions. This variational principle is symmetric under permutations of the discrete space-time points. We explain how for minimizers of the variational principle, the fermions spontaneously break this permutation symmetry and induce on space-time a discrete causal structure.

Fermion Systems in Discrete Space-Time

OpenAIRE

Finster, Felix

2006-01-01

Fermion systems in discrete space-time are introduced as a model for physics on the Planck scale. We set up a variational principle which describes a non-local interaction of all fermions. This variational principle is symmetric under permutations of the discrete space-time points. We explain how for minimizers of the variational principle, the fermions spontaneously break this permutation symmetry and induce on space-time a discrete causal structure.

Fermion systems in discrete space-time

Science.gov (United States)

Finster, Felix

2007-05-01

Fermion systems in discrete space-time are introduced as a model for physics on the Planck scale. We set up a variational principle which describes a non-local interaction of all fermions. This variational principle is symmetric under permutations of the discrete space-time points. We explain how for minimizers of the variational principle, the fermions spontaneously break this permutation symmetry and induce on space-time a discrete causal structure.

Holographic fermionic spectrum from Born–Infeld AdS black hole

Directory of Open Access Journals (Sweden)

Jian-Pin Wu

2016-07-01

Full Text Available In this letter, we systematically explore the holographic (non-relativistic fermionic spectrum without/with dipole coupling dual to Born–Infeld anti-de Sitter (BI-AdS black hole. For the relativistic fermionic fixed point, this holographic fermionic system exhibits non-Fermi liquid behavior. Also, with the increase of BI parameter γ, the non-Fermi liquid becomes even “more non-Fermi”. When the dipole coupling term is included, we find that the BI term makes it a lot tougher to form the gap. While for the non-relativistic fermionic system with large dipole coupling in BI-AdS background, with the increase of BI parameter, the gap comes into being again.

Universality of the quasinormal spectrum of near-extremal Kerr-Newman black holes

Energy Technology Data Exchange (ETDEWEB)

Hod, Shahar [The Ruppin Academic Center, Emeq Hefer (Israel); The Hadassah Institute, Jerusalem (Israel)

2015-06-15

Our current knowledge about the quasinormal resonance spectrum of charged and rotating Kerr-Newman black holes is quite poor. This unsatisfactory situation is a direct consequence of the fact that all attempts to decouple the gravitational and electromagnetic perturbations of generic Kerr-Newman black holes have failed thus far. Recently, Zilhao et al. (Phys Rev D 90:12, 124088, 2014. arXiv:1410.0694) have studied the nonlinear stability of Kerr-Newman black holes. We show here that their numerical results for the time evolutions of the spacetime deformations of near-extremal Kerr-Newman black holes are described extremely well by a simple and universal analytical formula for the quasinormal resonances of the black holes. This formula is expressed in terms of the black-hole physical parameters: the horizon angular velocity Ω{sub H} and the Bekenstein-Hawking temperature T{sub BH}. (orig.)

Hawking Radiation-Quasinormal Modes Correspondence for Large AdS Black Holes

Directory of Open Access Journals (Sweden)

Dao-Quan Sun

2017-01-01

Full Text Available It is well-known that the nonstrictly thermal character of the Hawking radiation spectrum generates a natural correspondence between Hawking radiation and black hole quasinormal modes. This main issue has been analyzed in the framework of Schwarzschild black holes, Kerr black holes, and nonextremal Reissner-Nordstrom black holes. In this paper, by introducing the effective temperature, we reanalyze the nonstrictly thermal character of large AdS black holes. The results show that the effective mass corresponding to the effective temperature is approximatively the average one in any dimension. And the other effective quantities can also be obtained. Based on the known forms of frequency in quasinormal modes, we reanalyze the asymptotic frequencies of the large AdS black hole in three and five dimensions. Then we get the formulas of the Bekenstein-Hawking entropy and the horizon’s area quantization with functions of the quantum “overtone” number n.

Geometry of non-degenerate Susskind fermions

International Nuclear Information System (INIS)

Mitra, P.

1983-01-01

The Dirac-Kaehler equation on the lattice is known to describe the degenerate ''flavours'' appering in Susskind's approach to lattice fermions. We study the modification that has to be made in this equation in order to lift the degeneracy and give the flavours arbitrary different masses. (orig.)

Spectral properties of embedded Gaussian unitary ensemble of random matrices with Wigner's SU(4) symmetry

International Nuclear Information System (INIS)

Vyas, Manan; Kota, V.K.B.

2010-01-01

For m fermions in Ω number of single particle orbitals, each fourfold degenerate, we introduce and analyze in detail embedded Gaussian unitary ensemble of random matrices generated by random two-body interactions that are SU(4) scalar [EGUE(2)-SU(4)]. Here the SU(4) algebra corresponds to the Wigner's supermultiplet SU(4) symmetry in nuclei. Embedding algebra for the EGUE(2)-SU(4) ensemble is U(4Ω) contains U(Ω) x SU(4). Exploiting the Wigner-Racah algebra of the embedding algebra, analytical expression for the ensemble average of the product of any two m particle Hamiltonian matrix elements is derived. Using this, formulas for a special class of U(Ω) irreducible representations (irreps) {4 r , p}, p = 0, 1, 2, 3 are derived for the ensemble averaged spectral variances and also for the covariances in energy centroids and spectral variances. On the other hand, simplifying the tabulations of Hecht for SU(Ω) Racah coefficients, numerical calculations are carried out for general U(Ω) irreps. Spectral variances clearly show, by applying Jacquod and Stone prescription, that the EGUE(2)-SU(4) ensemble generates ground state structure just as the quadratic Casimir invariant (C 2 ) of SU(4). This is further corroborated by the calculation of the expectation values of C 2 [SU(4)] and the four periodicity in the ground state energies. Secondly, it is found that the covariances in energy centroids and spectral variances increase in magnitude considerably as we go from EGUE(2) for spinless fermions to EGUE(2) for fermions with spin to EGUE(2)-SU(4) implying that the differences in ensemble and spectral averages grow with increasing symmetry. Also for EGUE(2)-SU(4) there are, unlike for GUE, non-zero cross-correlations in energy centroids and spectral variances defined over spaces with different particle numbers and/or U(Ω) [equivalently SU(4)] irreps. In the dilute limit defined by Ω → ∞, r >> 1 and r/Ω → 0, for the {4 r , p} irreps, we have derived analytical

Path integral for gauge theories with fermions

International Nuclear Information System (INIS)

Fujikawa, K.

1980-01-01

The Atiyah-Singer index theorem indicates that a naive unitary transformation of basis vectors for fermions interacting with gauge fields is not allowed in general. On the basis of this observation, it was previously shown that the path-integral measure of a gauge-invariant fermion theory is transformed nontrivially under the chiral transformation, and thus leads to a simple derivation of ''anomalous'' chiral Ward-Takahashi identities. We here clarify some of the technical aspects associated with the discussion. It is shown that the Jacobian factor in the path-integral measure, which corresponds to the Adler-Bell-Jackiw anomaly, is independent of any smooth regularization procedure of large eigenvalues of D in Euclidean theory; this property holds in any even-dimensional space-time and also for the gravitational anomaly. The appearance of the anomaly and its connection with the index theorem are thus related to the fact that the primary importance is attached to the Lorentz-covariant ''energy'' operator D and that D and γ 5 do not commute. The abnormal behavior of the path-integral measure at the zero-frequency sector in the presence of instantons and its connection with spontaneous symmetry breaking is also clarified. We comment on several other problems associated with the anomaly and on the Pauli-Villars regularization method

The representation theory of the symmetry group of lattice fermions as a basis for kinematics in lattice QCD

International Nuclear Information System (INIS)

Joos, H.; Schaefer, M.

1987-01-01

The symmetry group of staggered lattice fermions is discussed as a discrete subgroup of the symmetry group of the Dirac-Kaehler equation. For the representation theory of this group, G. Mackey's generalization of E.P. Wigner's procedure for the construction of unitary representations of groups with normal subgroups is used. A complete classification of these irreducible representations by ''momentum stars'', ''flavour orbits'' and ''reduced spins'' is given. (orig.)

A unified approach to the minimal unitary realizations of noncompact groups and supergroups

International Nuclear Information System (INIS)

Guenaydin, Murat; Pavlyk, Oleksandr

2006-01-01

We study the minimal unitary representations of non-compact groups and supergroups obtained by quantization of their geometric realizations as quasi-conformal groups and supergroups. The quasi-conformal groups G leave generalized light-cones defined by a quartic norm invariant and have maximal rank subgroups of the form H x SL(2, R) such that G/H x SL(2, R) are para-quaternionic symmetric spaces. We give a unified formulation of the minimal unitary representations of simple non-compact groups of type A 2 , G 2 , D 4 , F 4 , E 6 , E 7 , E 8 and Sp(2n, R). The minimal unitary representations of Sp(2n, R) are simply the singleton representations and correspond to a degenerate limit of the unified construction. The minimal unitary representations of the other noncompact groups SU(m, n), SO(m, n), SO*(2n) and SL(m, R) are also given explicitly. We extend our formalism to define and construct the corresponding minimal representations of non-compact supergroups G whose even subgroups are of the form H x SL(2, R). If H is noncompact then the supergroup G does not admit any unitary representations, in general. The unified construction with H simple or Abelian leads to the minimal representations of G(3), F(4) and O Sp(n|2, R) (in the degenerate limit). The minimal unitary representations of O Sp(n|2, R) with even subgroups SO(n) x SL(2, R) are the singleton representations. We also give the minimal realization of the one parameter family of Lie superalgebras D(2, 1; σ)

Unitary Transformation in Quantum Teleportation

International Nuclear Information System (INIS)

Wang Zhengchuan

2006-01-01

In the well-known treatment of quantum teleportation, the receiver should convert the state of his EPR particle into the replica of the unknown quantum state by one of four possible unitary transformations. However, the importance of these unitary transformations must be emphasized. We will show in this paper that the receiver cannot transform the state of his particle into an exact replica of the unknown state which the sender wants to transfer if he has not a proper implementation of these unitary transformations. In the procedure of converting state, the inevitable coupling between EPR particle and environment which is needed by the implementation of unitary transformations will reduce the accuracy of the replica.

Chiral anomaly, fermionic determinant and two dimensional models

International Nuclear Information System (INIS)

Rego Monteiro, M.A. do.

1985-01-01

The chiral anomaly in random pair dimension is analysed. This anomaly is perturbatively calculated by dimensional regularization method. A new method for non-perturbative Jacobian calculation of a general chiral transformation, 1.e., finite and non-Abelian, is developed. This method is used for non-perturbative chiral anomaly calculation, as an alternative to bosonization of two-dimensional theories for massless fermions and to study the phenomenum of fermion number fractionalization. The fermionic determinant from two-dimensional quantum chromodynamics is also studied, and calculated, exactly, as in decoupling gauge as with out reference to a particular gauge. (M.C.K.) [pt

Renormalization group running of fermion observables in an extended non-supersymmetric SO(10) model

Energy Technology Data Exchange (ETDEWEB)

Meloni, Davide [Dipartimento di Matematica e Fisica, Università di Roma Tre,Via della Vasca Navale 84, 00146 Rome (Italy); Ohlsson, Tommy; Riad, Stella [Department of Physics, School of Engineering Sciences,KTH Royal Institute of Technology - AlbaNova University Center,Roslagstullsbacken 21, 106 91 Stockholm (Sweden)

2017-03-08

We investigate the renormalization group evolution of fermion masses, mixings and quartic scalar Higgs self-couplings in an extended non-supersymmetric SO(10) model, where the Higgs sector contains the 10{sub H}, 120{sub H}, and 126{sub H} representations. The group SO(10) is spontaneously broken at the GUT scale to the Pati-Salam group and subsequently to the Standard Model (SM) at an intermediate scale M{sub I}. We explicitly take into account the effects of the change of gauge groups in the evolution. In particular, we derive the renormalization group equations for the different Yukawa couplings. We find that the computed physical fermion observables can be successfully matched to the experimental measured values at the electroweak scale. Using the same Yukawa couplings at the GUT scale, the measured values of the fermion observables cannot be reproduced with a SM-like evolution, leading to differences in the numerical values up to around 80%. Furthermore, a similar evolution can be performed for a minimal SO(10) model, where the Higgs sector consists of the 10{sub H} and 126{sub H} representations only, showing an equally good potential to describe the low-energy fermion observables. Finally, for both the extended and the minimal SO(10) models, we present predictions for the three Dirac and Majorana CP-violating phases as well as three effective neutrino mass parameters.

Area spectrum of extremal Reissner-Nordstroem black holes from quasinormal modes

International Nuclear Information System (INIS)

Setare, M.R.

2004-01-01

Using the quasinormal mode frequency of extremal Reissner-Nordstroem black holes, we obtain the area spectrum for these types of black holes. We show that the area and entropy black hole horizon are equally spaced. Our results for the spacing of the area spectrum differ from that for Schwarzschild black holes

Teleportation of M-Qubit Unitary Operations

Institute of Scientific and Technical Information of China (English)

郑亦庄; 顾永建; 郭光灿

2002-01-01

We discuss teleportation of unitary operations on a two-qubit in detail, then generalize the bidirectional state teleportation scheme from one-qubit to M-qubit unitary operations. The resources required for the optimal implementation of teleportation of an M-qubit unitary operation using a bidirectional state teleportation scheme are given.

Dynamic origins of fermionic D -terms

Science.gov (United States)

Hudson, Jonathan; Schweitzer, Peter

2018-03-01

The D -term is defined through matrix elements of the energy-momentum tensor, similarly to mass and spin, yet this important particle property is experimentally not known any fermion. In this work we show that the D -term of a spin 1/2 fermion is of dynamical origin: it vanishes for a free fermion. This is in pronounced contrast to the bosonic case where already a free spin-0 boson has a non-zero intrinsic D -term. We illustrate in two simple models how interactions generate the D -term of a fermion with an internal structure, the nucleon. All known matter is composed of elementary fermions. This indicates the importance to study this interesting particle property in more detail, which will provide novel insights especially on the structure of the nucleon.

Spectral intensity distribution of trapped fermions

Indian Academy of Sciences (India)

Trapped fermions; local density approximation; spectral intensity distribution function. ... Thus, cold atomic systems allow us to study interesting ... In fermions, synthetic non-Abelian gauge ... energy eigenstates of the isotropic harmonic oscillator [26–28]. ... d i=1. (ni + 1. 2. )ω0. In calculating the SIDF exactly these eigenfunc-.

New unitary affine-Virasoro constructions

International Nuclear Information System (INIS)

Halpern, M.B.; Kiritsis, E.; Obers, N.A.; Poratti, M.; Yamron, J.P.

1990-01-01

This paper reports on a quasi-systematic investigation of the Virasoro master equation. The space of all affine-Virasoro constructions is organized by K-conjugation into affine-Virasoro nests, and an estimate of the dimension of the space shows that most solutions await discovery. With consistent ansatze for the master equation, large classes of new unitary nests are constructed, including quadratic deformation nests with continuous conformal weights, and unitary irrational central charge nests, which may dominate unitary rational central charge on compact g

Fermion field as inflaton, dark energy and dark matter

International Nuclear Information System (INIS)

Grams, Guilherme; Souza, Rudinei C de; Kremer, Gilberto M

2014-01-01

The search for constituents that can explain the periods of accelerating expansion of the Universe is a fundamental topic in cosmology. In this context, we investigate how fermionic fields minimally and non-minimally coupled with the gravitational field may be responsible for accelerated regimes during the evolution of the Universe. The forms of the potential and coupling of the model are determined through the technique of the Noether symmetry for two cases. The first case comprises a Universe filled only with the fermion field. Cosmological solutions are straightforwardly obtained for this case and an exponential inflation mediated by the fermion field is possible with a non-minimal coupling. The second case takes account of the contributions of radiation and baryonic matter in the presence of the fermion field. In this case the fermion field plays the role of dark energy and dark matter, and when a non-minimal coupling is allowed, it mediates a power-law inflation. (paper)

Unitary transformations in solid state physics

International Nuclear Information System (INIS)

Wagner, M.

1986-01-01

The main emphasis of this book is on the practical application of unitary transformations to problems in solid state physics. This is a method used in the field of nonadiabatic electron-phonon phenomena where the Born-Oppenheimer approximation is no longer applicable. The book is intended as a tool for those who want to apply unitary transformations quickly and on a more elementary level and also for those who want to use this method for more involved problems. The book is divided into 6 chapters. The first three chapters are concerned with presenting quick applications of unitary transformations and chapter 4 presents a more systematic procedure. The last two chapters contain the major known examples of the utilization of unitary transformations in solid state physics, including such highlights as the Froehlich and the Fulton-Gouterman transformations. The book is supplemented by extended tables of unitary transformations, whose properties and peculiarities are also listed. This tabulated material is unique and will be of great practical use to those applying the method of unitary transformations in their work. (Auth.)

Entanglement-continuous unitary transformations

Energy Technology Data Exchange (ETDEWEB)

Sahin, Serkan; Orus, Roman [Institute of Physics, Johannes Gutenberg University, 55099 Mainz (Germany)

2016-07-01

In this talk we present a new algorithm for quantum many-body systems using continuous unitary transformations (CUT) and tensor networks (TNs). With TNs we are able to approximate the solution to the flow equations that lie at the heart of continuous unitary transformations. We call this method Entanglement-Continuous Unitary Transformations (eCUT). It allows us to compute expectation values of local observables as well as tensor network representations of ground states and low-energy excited states. An implementation of the method is shown for 1d systems using matrix product operators. We show preliminary results for the 1d transverse-field Ising model to demonstrate the feasibility of the method.

Strongly-interacting mirror fermions at the LHC

Directory of Open Access Journals (Sweden)

Triantaphyllou George

2017-01-01

Full Text Available The introduction of mirror fermions corresponding to an interchange of leftwith right-handed fermion quantum numbers of the Standard Model can lead to a model according to which the BEH mechanism is just an effective manifestation of a more fundamental theory while the recently-discovered Higgs-like particle is composite. This is achieved by a non-abelian gauge symmetry encompassing three mirror-fermion families strongly coupled at energies near 1 TeV. The corresponding non-perturbative dynamics lead to dynamical mirror-fermion masses between 0.14 - 1.2 TeV. Furthermore, one expects the formation of composite states, i.e. “mirror mesons”, with masses between 0.1 and 3 TeV. The number and properties of the resulting new degrees of freedom lead to a rich and interesting phenomenology, part of which is analyzed in the present work.

Wilson Fermions with Four Fermion Interactions

DEFF Research Database (Denmark)

Rantaharju, Jarno; Drach, Vincent; Hietanen, Ari

2015-01-01

We present a lattice study of a four fermion theory, known as Nambu Jona-Lasinio (NJL) theory, via Wilson fermions. Four fermion interactions naturally occur in several extensions of the Standard Model as a low energy parameterisation of a more fundamental theory. In models of dynamical electroweak...

Non-relativistic fermions, coadjoint orbits of W∞ and string field theory at c=1

International Nuclear Information System (INIS)

Dhar, A.; Mandal, G.; Wadia, S.R.

1992-01-01

In this paper, the authors apply the method of coadjoint orbits of W ∞ -algebra to the problem of non-relativistic fermions in one dimension. This leads to a geometric formulation of the quantum theory in terms of the quantum phase space distribution of the Fermi fluid. The action has an infinite series of expansion in the string coupling, which to leading order reduces to the previously discussed geometric action for the classical Fermi fluid based on the group w ∞ of area-preserving diffeomorphisms. The authors briefly discuss the strong coupling limit of the string theory which, unlike the weak coupling regime, does not seem to admit a two-dimensional space-time picture. The authors' methods are equally applicable to interacting fermions in one dimension

Fermion production despite fermion number conservation

International Nuclear Information System (INIS)

Bock, W.; Hetrick, J.E.; Smit, J.

1995-01-01

Lattice proposals for a nonperturbative formulation of the Standard Model easily lead to a global U(1) symmetry corresponding to exactly conserved fermion number. The absence of an anomaly in the fermion current would then appear to inhibit anomalous processes, such as electroweak baryogenesis in the early universe. One way to circumvent this problem is to formulate the theory such that this U(1) symmetry is explicitly broken. However we argue that in the framework of spectral flow, fermion creation and annihilation still in fact occurs, despite the exact fermion number conservation. The crucial observation is that fermions are excitations relative to the vacuum, at the surface of the Dirac sea. The exact global U(1) symmetry prohibits a state from changing its fermion number during time evolution, however nothing prevents the fermionic ground state from doing so. We illustrate our reasoning with a model in two dimensions which has axial-vector couplings, first using a sharp momentum cutoff, then using the lattice regulator with staggered fermions. The difference in fermion number between the time evolved state and the ground state is indeed in agreement with the anomaly. Both the sharp momentum cutoff and the lattice regulator break gauge invariance. In the case of the lattice model a mass counterterm for the gauge field is sufficient to restore gauge invariance in the perturbative regime. A study of the vacuum energy shows however that the perturbative counterterm is insufficient in a nonperturbative setting and that further quartic counterterms are needed. For reference we also study a closely related model with vector couplings, the Schwinger model, and we examine the emergence of the θ-vacuum structure of both theories. ((orig.))

Calculation of momentum distribution function of a non-thermal fermionic dark matter

Energy Technology Data Exchange (ETDEWEB)

Biswas, Anirban; Gupta, Aritra, E-mail: anirbanbiswas@hri.res.in, E-mail: aritra@hri.res.in [Harish-Chandra Research Institute, Chhatnag Road, Jhunsi, Allahabad 211 019 (India)

2017-03-01

The most widely studied scenario in dark matter phenomenology is the thermal WIMP scenario. Inspite of numerous efforts to detect WIMP, till now we have no direct evidence for it. A possible explanation for this non-observation of dark matter could be because of its very feeble interaction strength and hence, failing to thermalise with the rest of the cosmic soup. In other words, the dark matter might be of non-thermal origin where the relic density is obtained by the so-called freeze-in mechanism. Furthermore, if this non-thermal dark matter is itself produced substantially from the decay of another non-thermal mother particle, then their distribution functions may differ in both size and shape from the usual equilibrium distribution function. In this work, we have studied such a non-thermal (fermionic) dark matter scenario in the light of a new type of U(1){sub B−L} model. The U(1){sub B−L} model is interesting, since, besides being anomaly free, it can give rise to neutrino mass by Type II see-saw mechanism. Moreover, as we will show, it can accommodate a non-thermal fermionic dark matter as well. Starting from the collision terms, we have calculated the momentum distribution function for the dark matter by solving a coupled system of Boltzmann equations. We then used it to calculate the final relic abundance, as well as other relevant physical quantities. We have also compared our result with that obtained from solving the usual Boltzmann (or rate) equations directly in terms of comoving number density, Y . Our findings suggest that the latter approximation is valid only in cases where the system under study is close to equilibrium, and hence should be used with caution.

A remark on the unitary part of contractions

International Nuclear Information System (INIS)

Duggal, B.P.

1992-07-01

Considering operators on a complex infinite dimensional Hilbert space H and denoting by T * a construction with C .O completely non-unitary part, it is proved that A T is projection which commutes with T and H (u) T = A T H. 3 refs

Transport properties of chiral fermions

Energy Technology Data Exchange (ETDEWEB)

Puhr, Matthias

2017-04-26

Anomalous transport phenomena have their origin in the chiral anomaly, the anomalous non-conservation of the axial charge, and can arise in systems with chiral fermions. The anomalous transport properties of free fermions are well understood, but little is known about possible corrections to the anomalous transport coefficients that can occur if the fermions are strongly interacting. The main goal of this thesis is to study anomalous transport effects in media with strongly interacting fermions. In particular, we investigate the Chiral Magnetic Effect (CME) in a Weyl Semimetal (WSM) and the Chiral Separation Effect (CSE) in finite-density Quantum Chromodynamics (QCD). The recently discovered WSMs are solid state crystals with low-energy excitations that behave like Weyl fermions. The inter-electron interaction in WSMs is typically very strong and non-perturbative calculations are needed to connect theory and experiment. To realistically model an interacting, parity-breaking WSM we use a tight-binding lattice Hamiltonian with Wilson-Dirac fermions. This model features a non-trivial phase diagram and has a phase (Aoki phase/axionic insulator phase) with spontaneously broken CP symmetry, corresponding to the phase with spontaneously broken chiral symmetry for interacting continuum Dirac fermions. We use a mean-field ansatz to study the CME in spatially modulated magnetic fields and find that it vanishes in the Aoki phase. Moreover, our calculations show that outside of the Aoki phase the electron interaction has only a minor influence on the CME. We observe no enhancement of the magnitude of the CME current. For our non-perturbative study of the CSE in QCD we use the framework of lattice QCD with overlap fermions. We work in the quenched approximation to avoid the sign problem that comes with introducing a finite chemical potential on the lattice. The overlap operator calls for the evaluation of the sign function of a matrix with a dimension proportional to the volume

Second quantization and atomic spontaneous emission inside one-dimensional photonic crystals via a quasinormal-modes approach

International Nuclear Information System (INIS)

Severini, S.; Settimi, A.; Sibilia, C.; Bertolotti, M.; Napoli, A.; Messina, A.

2004-01-01

An extension of the second quantization scheme based on the quasinormal-modes theory to one-dimensional photonic band gap (PBG) structures is discussed. Such structures, treated as double open optical cavities, are studied as part of a compound closed system including the electromagnetic radiative external bath. The electromagnetic field inside the photonic crystal is successfully represented by a new class of modes called quasinormal modes. Starting from this representation we introduce the Feynman's propagator to calculate the decay rate of a dipole inside a PBG structure, related to the density of modes, in the presence of the vacuum fluctuations outside the one-dimensional cavity

Statistical quantization of GUT models and phase diagrams of W condensation for the Universe with finite fermion density

International Nuclear Information System (INIS)

Kalashnikov, O.K.; Razumov, L.V.; Perez Rojas, H.

1990-01-01

The problems of statistical quantization for grand-unified-theory models are studied using as an example the Weinberg-Salam model with finite fermion density under the conditions of neutral and electric charge conservation. The relativistic R γ gauge with an arbitrary parameter is used and the one-loop effective potential together with its extremum equations are found. We demonstrate (and this is our main result) that the thermodynamic potential obtained from the effective one, after the mass shell for ξ is used, remains gauge dependent if all temperature ranges (not only the leading high-temperature terms) are considered. The contradiction detected within the calculational scheme is eliminated after the redefinition of the model studied is made with the aid of the terms which are proportional to the ''non-Abelian'' chemical potential and equal to zero identically when the unitary gauge is fixed. The phase diagrams of the W condensation are established and all their peculiarities are displayed. We found for the universe with a zero neutral charge density that the W condensate occurs at any small fermion density ρ and appears at first near the point of symmetry restoration. For all ρ≠0 this condensate exists only in the finite-temperature domain and evaporates completely or partially when T goes to zero

Breit-Wigner resonances and the quasinormal modes of anti-de Sitter black holes

International Nuclear Information System (INIS)

Berti, Emanuele; Cardoso, Vitor; Pani, Paolo

2009-01-01

We show that the theory of Breit-Wigner resonances can be used as an efficient numerical tool to compute black hole quasinormal modes. For illustration, we focus on the Schwarzschild anti-de Sitter (SAdS) spacetime. The resonance method is better suited to small SAdS black holes than the traditional series expansion method, allowing us to confirm that the damping time scale of small SAdS black holes for scalar and gravitational fields is proportional to r + -2l-2 , where r + is the horizon radius. The proportionality coefficients are in good agreement with analytic calculations. We also examine the eikonal limit of SAdS quasinormal modes, confirming quantitatively Festuccia and Liu's [arXiv:0811.1033] prediction of the existence of very long-lived modes. Our results are particularly relevant for the AdS/CFT correspondence, since long-lived modes presumably dominate the decay time scale of the perturbations.

Entanglement quantification by local unitary operations

Energy Technology Data Exchange (ETDEWEB)

Monras, A.; Giampaolo, S. M.; Gualdi, G.; Illuminati, F. [Dipartimento di Matematica e Informatica, Universita degli Studi di Salerno, CNISM, Unita di Salerno, and INFN, Sezione di Napoli-Gruppo Collegato di Salerno, Via Ponte don Melillo, I-84084 Fisciano (Italy); Adesso, G.; Davies, G. B. [School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

2011-07-15

Invariance under local unitary operations is a fundamental property that must be obeyed by every proper measure of quantum entanglement. However, this is not the only aspect of entanglement theory where local unitary operations play a relevant role. In the present work we show that the application of suitable local unitary operations defines a family of bipartite entanglement monotones, collectively referred to as ''mirror entanglement.'' They are constructed by first considering the (squared) Hilbert-Schmidt distance of the state from the set of states obtained by applying to it a given local unitary operator. To the action of each different local unitary operator there corresponds a different distance. We then minimize these distances over the sets of local unitary operations with different spectra, obtaining an entire family of different entanglement monotones. We show that these mirror-entanglement monotones are organized in a hierarchical structure, and we establish the conditions that need to be imposed on the spectrum of a local unitary operator for the associated mirror entanglement to be faithful, i.e., to vanish in and only in separable pure states. We analyze in detail the properties of one particularly relevant member of the family, the ''stellar mirror entanglement'' associated with the traceless local unitary operations with nondegenerate spectra and equispaced eigenvalues in the complex plane. This particular measure generalizes the original analysis of S. M. Giampaolo and F. Illuminati [Phys. Rev. A 76, 042301 (2007)], valid for qubits and qutrits. We prove that the stellar entanglement is a faithful bipartite entanglement monotone in any dimension and that it is bounded from below by a function proportional to the linear entropy and from above by the linear entropy itself, coinciding with it in two- and three-dimensional spaces.

Entanglement quantification by local unitary operations

Science.gov (United States)

Monras, A.; Adesso, G.; Giampaolo, S. M.; Gualdi, G.; Davies, G. B.; Illuminati, F.

2011-07-01

Invariance under local unitary operations is a fundamental property that must be obeyed by every proper measure of quantum entanglement. However, this is not the only aspect of entanglement theory where local unitary operations play a relevant role. In the present work we show that the application of suitable local unitary operations defines a family of bipartite entanglement monotones, collectively referred to as “mirror entanglement.” They are constructed by first considering the (squared) Hilbert-Schmidt distance of the state from the set of states obtained by applying to it a given local unitary operator. To the action of each different local unitary operator there corresponds a different distance. We then minimize these distances over the sets of local unitary operations with different spectra, obtaining an entire family of different entanglement monotones. We show that these mirror-entanglement monotones are organized in a hierarchical structure, and we establish the conditions that need to be imposed on the spectrum of a local unitary operator for the associated mirror entanglement to be faithful, i.e., to vanish in and only in separable pure states. We analyze in detail the properties of one particularly relevant member of the family, the “stellar mirror entanglement” associated with the traceless local unitary operations with nondegenerate spectra and equispaced eigenvalues in the complex plane. This particular measure generalizes the original analysis of S. M. Giampaolo and F. Illuminati [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.76.042301 76, 042301 (2007)], valid for qubits and qutrits. We prove that the stellar entanglement is a faithful bipartite entanglement monotone in any dimension and that it is bounded from below by a function proportional to the linear entropy and from above by the linear entropy itself, coinciding with it in two- and three-dimensional spaces.

Entanglement quantification by local unitary operations

International Nuclear Information System (INIS)

Monras, A.; Giampaolo, S. M.; Gualdi, G.; Illuminati, F.; Adesso, G.; Davies, G. B.

2011-01-01

Invariance under local unitary operations is a fundamental property that must be obeyed by every proper measure of quantum entanglement. However, this is not the only aspect of entanglement theory where local unitary operations play a relevant role. In the present work we show that the application of suitable local unitary operations defines a family of bipartite entanglement monotones, collectively referred to as ''mirror entanglement.'' They are constructed by first considering the (squared) Hilbert-Schmidt distance of the state from the set of states obtained by applying to it a given local unitary operator. To the action of each different local unitary operator there corresponds a different distance. We then minimize these distances over the sets of local unitary operations with different spectra, obtaining an entire family of different entanglement monotones. We show that these mirror-entanglement monotones are organized in a hierarchical structure, and we establish the conditions that need to be imposed on the spectrum of a local unitary operator for the associated mirror entanglement to be faithful, i.e., to vanish in and only in separable pure states. We analyze in detail the properties of one particularly relevant member of the family, the ''stellar mirror entanglement'' associated with the traceless local unitary operations with nondegenerate spectra and equispaced eigenvalues in the complex plane. This particular measure generalizes the original analysis of S. M. Giampaolo and F. Illuminati [Phys. Rev. A 76, 042301 (2007)], valid for qubits and qutrits. We prove that the stellar entanglement is a faithful bipartite entanglement monotone in any dimension and that it is bounded from below by a function proportional to the linear entropy and from above by the linear entropy itself, coinciding with it in two- and three-dimensional spaces.

Gravitational quasinormal modes of static Einstein-Gauss-Bonnet anti-de Sitter black holes

Science.gov (United States)

Ma, Hong; Li, Jin

2018-04-01

In this paper, we describe quasinormal modes (QNMs) for gravitational perturbations of Einstein-Gauss-Bonnet black holes (BHs) in higher dimensional spacetimes, and derive the corresponding parameters of such black holes in three types of spacetime (flat, de Sitter (dS) and anti-de Sitter (AdS)). Our attention is concentrated on discussing the (in)stability of Einstein-Gauss-Bonnet AdS BHs through the temporal evolution of all types of gravitational perturbation fields (tensor, vector and scalar). It is concluded that the potential functions in vector and scalar gravitational perturbations have negative regions, which suppress quasinormal ringing. Furthermore, the influences of the Gauss-Bonnet coupling parameter α, the number of dimensions n and the angular momentum quantum number l on the Einstein-Gauss-Bonnet AdS BHs quasinormal spectrum are analyzed. The QNM frequencies have greater oscillation and lower damping rate with the growth of α. This indicates that QNM frequencies become increasingly unstable with large α. Meanwhile, the dynamic evolutions of the perturbation field are compliant with the results of computation from the Horowitz and Hubeny method. Because the number of extra dimensions is connected with the string scale, the relationship between α and properties of Einstein-Gauss-Bonnet AdS BHs might be beneficial for the exploitation of string theory and extra-dimensional brane worlds. Supported by FAPESP (2012/08934-0), National Natural Science Foundation of China (11205254, 11178018, 11375279, 11605015), the Natural Science Foundation Project of CQ CSTC (2011BB0052), and the Fundamental Research Funds for the Central Universities (106112016CDJXY300002, 106112017CDJXFLX0014, CDJRC10300003)

Axial anomalies of Lifshitz fermions

CERN Document Server

Bakas, Ioannis

2011-01-01

We compute the axial anomaly of a Lifshitz fermion theory with anisotropic scaling z=3 which is minimally coupled to geometry in 3+1 space-time dimensions. We find that the result is identical to the relativistic case using path integral methods. An independent verification is provided by showing with spectral methods that the eta-invariant of the Dirac and Lifshitz fermion operators in three dimensions are equal. Thus, by the integrated form of the anomaly, the index of the Dirac operator still accounts for the possible breakdown of chiral symmetry in non-relativistic theories of gravity. We apply this framework to the recently constructed gravitational instanton backgrounds of Horava-Lifshitz theory and find that the index is non-zero provided that the space-time foliation admits leaves with harmonic spinors. Using Hitchin's construction of harmonic spinors on Berger spheres, we obtain explicit results for the index of the fermion operator on all such gravitational instanton backgrounds with SU(2)xU(1) isom...

Interpolation between Airy and Poisson statistics for unitary chiral non-Hermitian random matrix ensembles

International Nuclear Information System (INIS)

Akemann, G.; Bender, M.

2010-01-01

We consider a family of chiral non-Hermitian Gaussian random matrices in the unitarily invariant symmetry class. The eigenvalue distribution in this model is expressed in terms of Laguerre polynomials in the complex plane. These are orthogonal with respect to a non-Gaussian weight including a modified Bessel function of the second kind, and we give an elementary proof for this. In the large n limit, the eigenvalue statistics at the spectral edge close to the real axis are described by the same family of kernels interpolating between Airy and Poisson that was recently found by one of the authors for the elliptic Ginibre ensemble. We conclude that this scaling limit is universal, appearing for two different non-Hermitian random matrix ensembles with unitary symmetry. As a second result we give an equivalent form for the interpolating Airy kernel in terms of a single real integral, similar to representations for the asymptotic kernel in the bulk and at the hard edge of the spectrum. This makes its structure as a one-parameter deformation of the Airy kernel more transparent.

Shear viscosity and imperfect fluidity in bosonic and fermionic superfluids

Science.gov (United States)

Boyack, Rufus; Guo, Hao; Levin, K.

2014-12-01

In this paper we address the ratio of the shear viscosity to entropy density η /s in bosonic and fermionic superfluids. A small η /s is associated with nearly perfect fluidity, and more general measures of the fluidity perfection/imperfection are of wide interest to a number of communities. We use a Kubo approach to concretely address this ratio via low-temperature transport associated with the quasiparticles. Our analysis for bosonic superfluids utilizes the framework of the one-loop Bogoliubov approximation, whereas for fermionic superfluids we apply BCS theory and its BCS-BEC extension. Interestingly, we find that the transport properties of strict BCS and Bogoliubov superfluids have very similar structures, albeit with different quasiparticle dispersion relations. While there is a dramatic contrast between the power law and exponential temperature dependence for η alone, the ratio η /s for both systems is more similar. Specifically, we find the same linear dependence (on the ratio of temperature T to inverse lifetime γ (T ) ) with η /s ∝T /γ (T ) , corresponding to imperfect fluidity. By contrast, near the unitary limit of BCS-BEC superfluids a very different behavior results, which is more consistent with near-perfect fluidity.

Semi-analytical quasi-normal mode theory for the local density of states in coupled photonic crystal cavity-waveguide structures

DEFF Research Database (Denmark)

de Lasson, Jakob Rosenkrantz; Kristensen, Philip Trøst; Mørk, Jesper

2015-01-01

We present and validate a semi-analytical quasi-normal mode (QNM) theory for the local density of states (LDOS) in coupled photonic crystal (PhC) cavity-waveguide structures. By means of an expansion of the Green's function on one or a few QNMs, a closed-form expression for the LDOS is obtained, ......-trivial spectrum with a peak and a dip is found, which is reproduced only when including both the two relevant QNMs in the theory. In both cases, we find relative errors below 1% in the bandwidth of interest.......We present and validate a semi-analytical quasi-normal mode (QNM) theory for the local density of states (LDOS) in coupled photonic crystal (PhC) cavity-waveguide structures. By means of an expansion of the Green's function on one or a few QNMs, a closed-form expression for the LDOS is obtained......, and for two types of two-dimensional PhCs, with one and two cavities side-coupled to an extended waveguide, the theory is validated against numerically exact computations. For the single cavity, a slightly asymmetric spectrum is found, which the QNM theory reproduces, and for two cavities a non...

Accretion-induced quasinormal mode excitation of a Schwarzschild black hole

International Nuclear Information System (INIS)

Nagar, Alessandro; Zanotti, Olindo; Font, Jose A.; Rezzolla, Luciano

2007-01-01

By combining the numerical solution of the nonlinear hydrodynamics equations with the solution of the linear inhomogeneous Zerilli-Moncrief and Regge-Wheeler equations, we investigate the properties of the gravitational radiation emitted during the axisymmetric accretion of matter onto a Schwarzschild black hole. The matter models considered include quadrupolar dust shells and thick accretion disks, permitting us to simulate situations which may be encountered at the end stages of stellar gravitational collapse or binary neutron star merger. We focus on the interference pattern appearing in the energy spectra of the emitted gravitational waves and on the amount of excitation of the quasinormal modes of the accreting black hole. We show that, quite generically in the presence of accretion, the black-hole ringdown is not a simple superposition of quasinormal modes, although the fundamental mode is usually present and often dominates the gravitational-wave signal. We interpret this as due to backscattering of waves off the nonexponentially decaying part of the black-hole potential and to the finite spatial extension of the accreting matter. Our results suggest that the black-hole QNM contributions to the full gravitational-wave signal should be extremely small and possibly not detectable in generic astrophysical scenarios involving the accretion of extended distributions of matter

Heavy-light fermion mixtures at unitarity

Energy Technology Data Exchange (ETDEWEB)

Gezerlis, Alexandros [Los Alamos National Laboratory; Carlson, Joseph [Los Alamos National Laboratory; Gandol, S [UNIV. ILL; Schmidt, E [ITALY

2009-01-01

We investigate fermion pairing in the unitary regime for a mass ratio corresponding to a {sup 6}Li-{sup 40}K mixture using quantum Monte Carlo methods. The ground-state energy and the average light- and heavy-particle excitation spectrum for the unpolarized superfluid state are nearly independent of the mass ratio. In the majority light system, the polarized superfluid is close to the energy of a phase separated mixture of nearly fully polarized normal and unpolarized superfluid. For a majority of heavy particles, we find an energy minimum for a normal state with a ratio of {approx}3:1 heavy to light particles. A slight increase in attraction to k{sub F}a{approx}2.5 yields a ground state energy of nearly zero for this ratio. A cold unpolarized system in a harmonic trap at unitarity should phase separate into three regions, with a shell of unpolarized superfluid in the middle.

Liouville equation of relativistic charged fermion

International Nuclear Information System (INIS)

Wang Renchuan; Zhu Dongpei; Huang Zhuoran; Ko Che-ming

1991-01-01

As a form of density martrix, the Wigner function is the distribution in quantum phase space. It is a 2 X 2 matrix function when one uses it to describe the non-relativistic fermion. While describing the relativistic fermion, it is usually represented by 4 x 4 matrix function. In this paper authors obtain a Wigner function for the relativistic fermion in the form of 2 x 2 matrix, and the Liouville equation satisfied by the Wigner function. this equivalent to the Dirac equation of changed fermion in QED. The equation is also equivalent to the Dirac equation in the Walecka model applied to the intermediate energy nuclear collision while the nucleon is coupled to the vector meson only (or taking mean field approximation for the scalar meson). Authors prove that the 2 x 2 Wigner function completely describes the quantum system just the same as the relativistic fermion wave function. All the information about the observables can be obtained with above Wigner function

Behavior of quasinormal modes and high dimension RN-AdS black hole phase transition

Energy Technology Data Exchange (ETDEWEB)

Chabab, M.; Iraoui, S.; Masmar, K. [Cadi Ayyad University, High Energy Physics and Astrophysics Laboratory, Faculty of Science Semlalia, Marrakesh (Morocco); El Moumni, H. [Cadi Ayyad University, High Energy Physics and Astrophysics Laboratory, Faculty of Science Semlalia, Marrakesh (Morocco); Ibn Zohr University, LMTI, Physics Department, Faculty of Sciences, Agadir (Morocco)

2016-12-15

In this work we use the quasinormal frequencies of a massless scalar perturbation to probe the phase transition of the high dimension charged AdS black hole. The signature of the critical behavior of this black hole solution is detected in the isobaric as well as in isothermal process. This paper is a natural generalization of Liu et al. (JHEP 1409:179, 2014) to higher dimensional spacetime. More precisely our study shows a clear signal for any dimension d in the isobaric process. As to the isothermal case, we find that this signature can be affected by other parameters like the pressure and the horizon radius. We conclude that the quasinormal modes can be an efficient tool to investigate the first-order phase transition, but fail to disclose the signature of the second-order phase transition. (orig.)

Wigner functions for fermions in strong magnetic fields

Science.gov (United States)

Sheng, Xin-li; Rischke, Dirk H.; Vasak, David; Wang, Qun

2018-02-01

We compute the covariant Wigner function for spin-(1/2) fermions in an arbitrarily strong magnetic field by exactly solving the Dirac equation at non-zero fermion-number and chiral-charge densities. The Landau energy levels as well as a set of orthonormal eigenfunctions are found as solutions of the Dirac equation. With these orthonormal eigenfunctions we construct the fermion field operators and the corresponding Wigner-function operator. The Wigner function is obtained by taking the ensemble average of the Wigner-function operator in global thermodynamical equilibrium, i.e., at constant temperature T and non-zero fermion-number and chiral-charge chemical potentials μ and μ_5, respectively. Extracting the vector and axial-vector components of the Wigner function, we reproduce the currents of the chiral magnetic and separation effect in an arbitrarily strong magnetic field.

Implementability of two-qubit unitary operations over the butterfly network and the ladder network with free classical communication

Energy Technology Data Exchange (ETDEWEB)

Akibue, Seiseki [Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo (Japan); Murao, Mio [Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo, Japan and NanoQuine, The University of Tokyo, Tokyo (Japan)

2014-12-04

We investigate distributed implementation of two-qubit unitary operations over two primitive networks, the butterfly network and the ladder network, as a first step to apply network coding for quantum computation. By classifying two-qubit unitary operations in terms of the Kraus-Cirac number, the number of non-zero parameters describing the global part of two-qubit unitary operations, we analyze which class of two-qubit unitary operations is implementable over these networks with free classical communication. For the butterfly network, we show that two classes of two-qubit unitary operations, which contain all Clifford, controlled-unitary and matchgate operations, are implementable over the network. For the ladder network, we show that two-qubit unitary operations are implementable over the network if and only if their Kraus-Cirac number do not exceed the number of the bridges of the ladder.

Implementability of two-qubit unitary operations over the butterfly network and the ladder network with free classical communication

International Nuclear Information System (INIS)

Akibue, Seiseki; Murao, Mio

2014-01-01

We investigate distributed implementation of two-qubit unitary operations over two primitive networks, the butterfly network and the ladder network, as a first step to apply network coding for quantum computation. By classifying two-qubit unitary operations in terms of the Kraus-Cirac number, the number of non-zero parameters describing the global part of two-qubit unitary operations, we analyze which class of two-qubit unitary operations is implementable over these networks with free classical communication. For the butterfly network, we show that two classes of two-qubit unitary operations, which contain all Clifford, controlled-unitary and matchgate operations, are implementable over the network. For the ladder network, we show that two-qubit unitary operations are implementable over the network if and only if their Kraus-Cirac number do not exceed the number of the bridges of the ladder

Fermionic solution of the Andrews-Baxter-Forrester model. II. Proof of Melzer's polynomial identities

International Nuclear Information System (INIS)

Warnaar, S.O.

1996-01-01

We compute the one-dimensional configuration sums of the AFB model using the fermionic techniques introduced in part I of this paper. Combined with the results of Andrews, Baxter, and Forrester, we prove polynominal identities for finitizations of the Virasoro characters χb, a (r-1, r) (q) as conjectured by Melzer. In the thermodynamic limit these identities reproduce Rogers-Ramanujan-type identities for the unitary minimal Virasoro characters conjectured by the Stony Brook group. We also present a list of additional Virasoro character identities which follow from our proof of Melzer's identities and application of Bailey's lemma

Optimal quantum learning of a unitary transformation

International Nuclear Information System (INIS)

Bisio, Alessandro; Chiribella, Giulio; D'Ariano, Giacomo Mauro; Facchini, Stefano; Perinotti, Paolo

2010-01-01

We address the problem of learning an unknown unitary transformation from a finite number of examples. The problem consists in finding the learning machine that optimally emulates the examples, thus reproducing the unknown unitary with maximum fidelity. Learning a unitary is equivalent to storing it in the state of a quantum memory (the memory of the learning machine) and subsequently retrieving it. We prove that, whenever the unknown unitary is drawn from a group, the optimal strategy consists in a parallel call of the available uses followed by a 'measure-and-rotate' retrieving. Differing from the case of quantum cloning, where the incoherent 'measure-and-prepare' strategies are typically suboptimal, in the case of learning the 'measure-and-rotate' strategy is optimal even when the learning machine is asked to reproduce a single copy of the unknown unitary. We finally address the problem of the optimal inversion of an unknown unitary evolution, showing also in this case the optimality of the 'measure-and-rotate' strategies and applying our result to the optimal approximate realignment of reference frames for quantum communication.

Phases of renormalized lattice gauge theories with fermions

International Nuclear Information System (INIS)

Caracciolo, S.; Menotti, P.; and INFN Sezione di Pisa, Italy)

1979-01-01

Starting from the formulation of gauge theories on a lattice we derive renormalization group transformation of the Migdal-Kadanoff type in the presence of fermions. We consider the effect of the fermion vacuum polarization on the gauge Lagrangian but we neglect fermion mass renormalization. We work out the weak coupling and strong coupling expansion in the same framework. Asymptotic freedom is recovered for the non-Abelian case provided the number of fermion multiplets is lower than a critical number. Fixed points are determined both for the U (1) and SU (2) case. We determine the renormalized trajectories and the phases of the theory

Normed Orlicz function spaces which can be quasi-renormed with easily calculable quasinorms

Czech Academy of Sciences Publication Activity Database

Foralewski, P.; Hudzik, H.; Kaczmarek, R.; Krbec, Miroslav

2017-01-01

Roč. 11, č. 3 (2017), s. 636-660 ISSN 1735-8787 Institutional support: RVO:67985840 Keywords : embeddings into Lebesgue and weighted Lebesgue spaces * Orlicz spaces * quasinorms Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 0.833, year: 2016 http://projecteuclid.org/euclid.bjma/1496973700

Quantum unitary dynamics in cosmological spacetimes

International Nuclear Information System (INIS)

Cortez, Jerónimo; Mena Marugán, Guillermo A.; Velhinho, José M.

2015-01-01

We address the question of unitary implementation of the dynamics for scalar fields in cosmological scenarios. Together with invariance under spatial isometries, the requirement of a unitary evolution singles out a rescaling of the scalar field and a unitary equivalence class of Fock representations for the associated canonical commutation relations. Moreover, this criterion provides as well a privileged quantization for the unscaled field, even though the associated dynamics is not unitarily implementable in that case. We discuss the relation between the initial data that determine the Fock representations in the rescaled and unscaled descriptions, and clarify that the S-matrix is well defined in both cases. In our discussion, we also comment on a recently proposed generalized notion of unitary implementation of the dynamics, making clear the difference with the standard unitarity criterion and showing that the two approaches are not equivalent.

Quantum unitary dynamics in cosmological spacetimes

Energy Technology Data Exchange (ETDEWEB)

Cortez, Jerónimo, E-mail: jacq@ciencias.unam.mx [Departamento de Física, Facultad de Ciencias, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Mena Marugán, Guillermo A., E-mail: mena@iem.cfmac.csic.es [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid (Spain); Velhinho, José M., E-mail: jvelhi@ubi.pt [Departamento de Física, Faculdade de Ciências, Universidade da Beira Interior, R. Marquês D’Ávila e Bolama, 6201-001 Covilhã (Portugal)

2015-12-15

We address the question of unitary implementation of the dynamics for scalar fields in cosmological scenarios. Together with invariance under spatial isometries, the requirement of a unitary evolution singles out a rescaling of the scalar field and a unitary equivalence class of Fock representations for the associated canonical commutation relations. Moreover, this criterion provides as well a privileged quantization for the unscaled field, even though the associated dynamics is not unitarily implementable in that case. We discuss the relation between the initial data that determine the Fock representations in the rescaled and unscaled descriptions, and clarify that the S-matrix is well defined in both cases. In our discussion, we also comment on a recently proposed generalized notion of unitary implementation of the dynamics, making clear the difference with the standard unitarity criterion and showing that the two approaches are not equivalent.

Momentum distribution of non-interacting fermions enclosed in a box

International Nuclear Information System (INIS)

Krivine, H.

1985-01-01

This is a study of: the finite size effect on the momentum distribution n(/sup →/k) of an ensemble of A non-interacting fermions enclosed in a box. Analytical expressions are obtained in the two limiting cases the Fermi momentum. The result is to analyze the convergence of toward the standard step function in the infinite medium. Applying results to the nuclear case, changes are compared in n(/sup →/k) generated by the finite size of actual nuclei to those due to short range correlations. Both effects are shown to be of same order of magnitude. The next step is to take into account the short range correlations in finite systems

Construction of Non-Perturbative, Unitary Particle-Antiparticle Amplitudes for Finite Particle Number Scattering Formalisms

International Nuclear Information System (INIS)

Lindesay, James V

2002-01-01

Starting from a unitary, Lorentz invariant two-particle scattering amplitude, we show how to use an identification and replacement process to construct a unique, unitary particle-antiparticle amplitude. This process differs from conventional on-shell Mandelstam s,t,u crossing in that the input and constructed amplitudes can be off-diagonal and off-energy shell. Further, amplitudes are constructed using the invariant parameters which are appropriate to use as driving terms in the multi-particle, multichannel nonperturbative, cluster decomposable, relativistic scattering equations of the Faddeev-type integral equations recently presented by Alfred, Kwizera, Lindesay and Noyes. It is therefore anticipated that when so employed, the resulting multi-channel solutions will also be unitary. The process preserves the usual particle-antiparticle symmetries. To illustrate this process, we construct a J=0 scattering length model chosen for simplicity. We also exhibit a class of physical models which contain a finite quantum mass parameter and are Lorentz invariant. These are constructed to reduce in the appropriate limits, and with the proper choice of value and sign of the interaction parameter, to the asymptotic solution of the nonrelativistic Coulomb problem, including the forward scattering singularity , the essential singularity in the phase, and the Bohr bound-state spectrum

Bosonization of fermions coupled to topologically massive gravity

Science.gov (United States)

Fradkin, Eduardo; Moreno, Enrique F.; Schaposnik, Fidel A.

2014-03-01

We establish a duality between massive fermions coupled to topologically massive gravity (TMG) in d=3 space-time dimensions and a purely gravity theory which also will turn out to be a TMG theory but with different parameters: the original graviton mass in the TMG theory coupled to fermions picks up a contribution from fermion bosonization. We obtain explicit bosonization rules for the fermionic currents and for the energy-momentum tensor showing that the identifications do not depend explicitly on the parameters of the theory. These results are the gravitational analog of the results for 2+1 Abelian and non-Abelian bosonization in flat space-time.

Bosonization of fermions coupled to topologically massive gravity

International Nuclear Information System (INIS)

Fradkin, Eduardo; Moreno, Enrique F.; Schaposnik, Fidel A.

2014-01-01

We establish a duality between massive fermions coupled to topologically massive gravity (TMG) in d=3 space–time dimensions and a purely gravity theory which also will turn out to be a TMG theory but with different parameters: the original graviton mass in the TMG theory coupled to fermions picks up a contribution from fermion bosonization. We obtain explicit bosonization rules for the fermionic currents and for the energy–momentum tensor showing that the identifications do not depend explicitly on the parameters of the theory. These results are the gravitational analog of the results for 2+1 Abelian and non-Abelian bosonization in flat space–time.

Bosonization of fermions coupled to topologically massive gravity

Energy Technology Data Exchange (ETDEWEB)

Fradkin, Eduardo [Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, IL 61801-3080 (United States); Moreno, Enrique F. [Department of Physics, Northeastern University, Boston, MA 02115 (United States); Schaposnik, Fidel A. [Departamento de Física, Universidad Nacional de La Plata, Instituto de Física La Plata, C.C. 67, 1900 La Plata (Argentina)

2014-03-07

We establish a duality between massive fermions coupled to topologically massive gravity (TMG) in d=3 space–time dimensions and a purely gravity theory which also will turn out to be a TMG theory but with different parameters: the original graviton mass in the TMG theory coupled to fermions picks up a contribution from fermion bosonization. We obtain explicit bosonization rules for the fermionic currents and for the energy–momentum tensor showing that the identifications do not depend explicitly on the parameters of the theory. These results are the gravitational analog of the results for 2+1 Abelian and non-Abelian bosonization in flat space–time.

Factorizable S-matrix for SO(D)/SO(2) circle times SO(D - 2) non-linear σ models with fermions

International Nuclear Information System (INIS)

Abdalla, E.; Lima-Santos, A.

1988-01-01

The authors compute the exact S matrix for the non-linear sigma model with symmetry SO(D)/SO(2) circle times SO(D-2) coupled to fermions in a minimal or supersymmetric way. The model has some relevance in string theory with non-zero external curvature

Contributions of unitarity diagrams to the polarization of fermions

International Nuclear Information System (INIS)

Quadder, B.

1992-01-01

In this work the subject of large single spin observables of fermions is addressed. Such observables, as for instance the analyzing power in elastic proton scattering or the polarization of hyperons, are related to the imaginary part of a product of spin-flip and non-flip amplitudes. So both spin-flip and relative phases between spin-flip and non-flip amplitudes are required to achieve non-vanishing single spin asymmetries. In the framework of perturbative Quantum Chromodynamics the asymmetry arises from the subprocess level. For massless quarks no spin-flips occur, because the coupling to spin 1-gluons conserves helicity. If the quarks are massive or particles with other spin than 1/2 are considered, the helicity conservation no longer holds. The born amplitudes are real, so the phases come from the second order box diagrams. An efficient method due to Charap and Leader to calculate the imaginary part of such unitarity diagrams is investigated. With the aid of the general unitary condition for particles with arbitrary spins the evaluation of the imaginary part of a second order amplitude is traced back to an integration of the product of two born amplitudes over the relative angles. With this method the imaginary part of the helicity amplitudes for several subprocesses is calculated. The polarization in quark subprocesses with massive quarks is small. So we conclude that non-perturbative aspects are essential. As a model for non-perturbative effects we incorporate diquarks. They are considered as quasi-elementary constituents, beside quarks, within bayrons, which also take an active part in reactions in an medium range of momentum transfer. Spin 1-Diquarks constitute spin-flips on the born level. In order to investigate the polarization effects from quark and diquark subprocesses they were compared in different exclusive reactions within the framework of the spectator model. (orig./HSI) [de

Bosonization of non-relativistic fermions and W-infinity algebra

International Nuclear Information System (INIS)

Das, S.R.; Dhar, A.; Mandal, G.; Wadia, S.R.

1992-01-01

In this paper the authors discuss the bosonization of non-relativistic fermions in one-space dimension in terms of bilocal operators which are naturally related to the generators of W-infinity algebra. The resulting system is analogous to the problem of a spin in a magnetic field for the group W-infinity. The new dynamical variables turn out to be W-infinity group elements valued in the coset W-infinity/H where H is a Cartan subalgebra. A classical action with an H gauge invariance is presented. This action is three-dimensional. It turns out to be similar to the action that describes the color degrees of freedom of a Yang-Mills particle in a fixed external field. The authors also discuss the relation of this action with the one recently arrived at in the Euclidean continuation of the theory using different coordinates

Quasinormal modes of BTZ black hole and Hawking-like radiation in graphene

Energy Technology Data Exchange (ETDEWEB)

Kandemir, B.S.; Ertem, Uemit [Department of Physics, Ankara University, Faculty of Sciences, 06100, Tandogan-Ankara (Turkey)

2017-04-15

The Banados-Teitelboim-Zanelli (BTZ) black hole model corresponds to a solution of (2+1)-dimensional Einstein gravity with negative cosmological constant, and by a conformal rescaling its metric can be mapped onto the hyperbolic pseudosphere surface (Beltrami trumpet) with negative curvature. Beltrami trumpet shaped graphene sheets have been predicted to emit Hawking radiation that is experimentally detectable by a scanning tunnelling microscope. Here, for the first time we present an analytical algorithm that allows variational solutions to the Dirac Hamiltonian of graphene pseudoparticles in BTZ black hole gravitational field by using an approach based on the formalism of pseudo-Hermitian Hamiltonians within a discrete-basis-set method. We show that our model not only reproduces the exact results for the real part of quasinormal mode frequencies of (2+1)-dimensional spinless BTZ black hole, but also provides analytical results for the real part of quasinormal modes of spinning BTZ black hole, and also offers some predictions for the observable effects with a view to gravity-like phenomena in a curved graphene sheet. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Charged Lifshitz black hole and probed Lorentz-violation fermions from holography

Energy Technology Data Exchange (ETDEWEB)

Luo, Cheng-Jian, E-mail: rocengeng@hotmail.com [Department of Physics, Nanchang University, Nanchang, 330031 (China); Center for Relativistic Astrophysics and High Energy Physics, Nanchang University, Nanchang 330031 (China); Kuang, Xiao-Mei, E-mail: xmeikuang@gmail.com [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile); Shu, Fu-Wen, E-mail: shufuwen@ncu.edu.cn [Department of Physics, Nanchang University, Nanchang, 330031 (China); Center for Relativistic Astrophysics and High Energy Physics, Nanchang University, Nanchang 330031 (China)

2017-06-10

We analytically obtain a new charged Lifshitz solution by adding a non-relativistic Maxwell field in Hořava–Lifshitz gravity. The black hole exhibits an anisotropic scaling between space and time (Lifshitz scaling) in the UV limit, while in the IR limit, the Lorentz invariance is approximately recovered. We introduce the probed Lorentz-violation fermions into the background and holographically investigate the spectral properties of the dual fermionic operator. The Lorentz-violation of the fermions will enhance the peak and correspond larger fermi momentum, which compensates the non-relativistic bulk effect of the dynamical exponent (z). For a fixed z, when the Lorentz-violation of fermions increases to a critical value, the behavior of the low energy excitation goes from a non-Fermi liquid type to a Fermi liquid type, which implies a kind of phase transition.

Higher dimensional unitary braid matrices: Construction, associated structures and entanglements

International Nuclear Information System (INIS)

Abdesselam, B.; Chakrabarti, A.; Dobrev, V.K.; Mihov, S.G.

2007-03-01

We construct (2n) 2 x (2n) 2 unitary braid matrices R-circumflex for n ≥ 2 generalizing the class known for n = 1. A set of (2n) x (2n) matrices (I, J,K,L) are defined. R-circumflex is expressed in terms of their tensor products (such as K x J), leading to a canonical formulation for all n. Complex projectors P ± provide a basis for our real, unitary R-circumflex. Baxterization is obtained. Diagonalizations and block- diagonalizations are presented. The loss of braid property when R-circumflex (n > 1) is block-diagonalized in terms of R-circumflex (n = 1) is pointed out and explained. For odd dimension (2n + 1) 2 x (2n + 1) 2 , a previously constructed braid matrix is complexified to obtain unitarity. R-circumflexLL- and R-circumflexTT- algebras, chain Hamiltonians, potentials for factorizable S-matrices, complex non-commutative spaces are all studied briefly in the context of our unitary braid matrices. Turaev construction of link invariants is formulated for our case. We conclude with comments concerning entanglements. (author)

The physics and chemistry of heavy Fermions

International Nuclear Information System (INIS)

Fisk, Z.; Sarrao, J.L.

1994-01-01

The heavy Fermions are a subset of the f-element intermetallics straddling the magnetic/non-magnetic boundary. Their low temperature properties are characterized by an electronic energy scale of order 1--10 K. Among the low temperature ground states observed in heavy Fermion compounds are exotic superconductors and magnets, as well as unusual semiconductors. We review here the current experimental and theoretical understanding of these systems

Fermion interactions with a Kaluza-Klein dyon

International Nuclear Information System (INIS)

Xi, Z.M.

1986-04-01

The fermion dynamics in the background of a five-dimensional Kaluza-Klein dyon is studied. It is found that the hamiltonian is self-adjoint despite the singular nature of the origin, and the fermion scattering on the dyon in the lowest angular momentum j = 0 channel is a helicity flip process. The possibility for charge-exchange process in the non-Abelian Kaluza-Klein theories is discussed

Moduli spaces of unitary conformal field theories

International Nuclear Information System (INIS)

Wendland, K.

2000-08-01

We investigate various features of moduli spaces of unitary conformal field theories. A geometric characterization of rational toroidal conformal field theories in arbitrary dimensions is presented and discussed in relation to singular tori and those with complex multiplication. We study the moduli space M 2 of unitary two-dimensional conformal field theories with central charge c = 2. All the 26 non-exceptional non-isolated irreducible components of M 2 are constructed that may be obtained by an orbifold procedure from toroidal theories. The parameter spaces and partition functions are calculated explicitly. All multicritical points and lines are determined, such that all but three of these 26 components are directly or indirectly connected to the space of toroidal theories in M 2 . Relating our results to those by Dixon, Ginsparg, Harvey on the classification of c = 3/2 superconformal field theories, we give geometric interpretations to all non-isolated orbifolds discussed by them and correct their statements on multicritical points within the moduli space of c = 3/2 superconformal field theories. In the main part of this work, we investigate the moduli space M of N = (4, 4) superconformal field theories with central charge c = 6. After a slight emendation of its global description we give generic partition functions for models contained in M. We explicitly determine the locations of various known models in the component of M associated to K3 surfaces

Meditations on the unitary rhythm of dying-grieving.

Science.gov (United States)

Malinski, Violet M

2012-07-01

When someone faces loss of a loved one, that person simultaneously grieves and dies a little, just as the one dying also grieves. The author's personal conceptualization of dying and grieving as a unitary rhythm is explored based primarily on her interpretation of Rogers' science of unitary human beings, along with selected examples from related nursing literature and from the emerging focus on continuing bonds in other disciplines. Examples from contemporary songwriters that depict such a unitary conceptualization are given along with personal examples. The author concludes with her description of the unitary rhythm of dying-grieving.

Quasinormal modes of a massless charged scalar field on a small Reissner-Nordstroem-anti-de Sitter black hole

International Nuclear Information System (INIS)

Uchikata, Nami; Yoshida, Shijun

2011-01-01

We investigate quasinormal modes of a massless charged scalar field on a small Reissner-Nordstroem-anti-de Sitter (RN-AdS) black hole both with analytical and numerical approaches. In the analytical approach, by using the small black hole approximation (r + + /L→0, where r + and L stand for the black hole event horizon radius and the AdS scale, respectively. We then show that the small RN-AdS black hole is unstable if its quasinormal modes satisfy the superradiance condition and that the instability condition of the RN-AdS black hole in the limit of r + /L→0 is given by Q>(3/eL)Q c , where Q, Q c , and e are the charge of the black hole, the critical (maximum) charge of the black hole, and the charge of the scalar field, respectively. In the numerical approach, we calculate the quasinormal modes for the small RN-AdS black holes with r + + =0.2L, 0.1L, and 0.01L become unstable against scalar perturbations with eL=4 when the charge of the black hole satisfies Q > or approx. 0.8Q c , 0.78Q c , and 0.76Q c , respectively.

The unitary space of particle internal states

International Nuclear Information System (INIS)

Perjes, Z.

1978-09-01

A relativistic theory of particle internal properties has been developed. Suppressing space-time information, internal wave functions and -observables are constructed in a 3-complex-dimensional space. The quantum numbers of a spinning point particle in this unitary space correspond with those of a low-mass hadron. Unitary space physics is linked with space-time notions via the Penrose theory of twistors, where new flavors may be represented by many-twistor systems. It is shown here that a four-twistor particle fits into the unitary space picture as a system of two points with equal masses and oppositely pointing unitary spins. Quantum states fall into the ISU(3) irreducible representations discovered by Sparling and the author. Full details of the computation involving SU(3) recoupling techniques are given. (author)

Renormalization group analysis of order parameter fluctuations in fermionic superfluids

International Nuclear Information System (INIS)

Obert, Benjamin

2014-01-01

In this work fluctuation effects in two interacting fermion systems exhibiting fermionic s-wave superfluidity are analyzed with a modern renormalization group method. A description in terms of a fermion-boson theory allows an investigation of order parameter fluctuations already on the one-loop level. In the first project a quantum phase transition between a semimetal and a s-wave superfluid in a Dirac cone model is studied. The interplay between fermions and quantum critical fluctuations close to and at the quantum critical point at zero and finite temperatures are studied within a coupled fermion-boson theory. At the quantum critical point non-Fermi liquid and non-Gaussian behaviour emerge. Close to criticality several quantities as the susceptibility show a power law behaviour with critical exponents. We find an infinite correlation length in the entire semimetallic ground state also away from the quantum critical point. In the second project, the ground state of an s-wave fermionic superfluid is investigated. Here, the mutual interplay between fermions and order parameter fluctuations is studied, especially the impact of massless Goldstone fluctuations, which occur due to spontaneous breaking of the continuous U(1)-symmetry. Fermionic gap and bosonic order parameter are distinguished. Furthermore, the bosonic order parameter is decomposed in transverse and longitudinal fluctuations. The mixing between transverse and longitudinal fluctuations is included in our description. Within a simple truncation of the fermion-boson RG flow, we describe the fermion-boson theory for the first time in a consistent manner. Several singularities appear due the Goldstone fluctuations, which partially cancel due to symmetry. Our RG flow captures the correct infrared asymptotics of the system, where the collective excitations act as an interacting Bose gas. Lowest order Ward identities and the massless Goldstone mode are fulfilled in our truncation.

The Chiral Index of the Fermionic Signature Operator

OpenAIRE

Finster, Felix

2014-01-01

We define an index of the fermionic signature operator on even-dimensional globally hyperbolic spin manifolds of finite lifetime. The invariance of the index under homotopies is studied. The definition is generalized to causal fermion systems with a chiral grading. We give examples of space-times and Dirac operators thereon for which our index is non-trivial.

Exotic fermions in the left-right symmetric model

International Nuclear Information System (INIS)

Choi, J.; Volkas, R.R.

1992-01-01

A systematic study is made of non-standard fermion multiplets in left-right symmetric models with gauge group SU(3) x SU(2) L x SU(2) R x U(1) BL . Constraints from gauge anomaly cancellation and invariance of Yukawa coupling terms are used to define interesting classes of exotic fermions. The standard quark lepton spectrum of left-right symmetric models was identified as the simplest member of an infinite class. Phenomenological implications of the next simplest member of this class are then studied. Classes of exotic fermions which may couple to the standard fermions through doublet Higgs bosons were also considered, then shown that some of these exotics may be used to induce a generalised universal see-saw mechanism. 12 refs., 1 tab

Arbitrary spin fermions on the lattice

International Nuclear Information System (INIS)

Bullinaria, J.A.

1985-01-01

Lattice actions are constructed for free Dirac and Majorana fermions of arbitrary (half-integer) spin various extensions of the spin 1/2 Kogut-Susskind, Kaehler and Wilson formalisms. In each case, the spectrum degeneracy and preservation of gauge invariance is analysed, and the equivalence or non-equivalence to previously constructed actions is determined. The Kogut-Susskind and lattice Kaehler actions are then written explicitly in terms of spinors to demonstrate how the degenerate fermions couple on the lattice and how the original spinorial actions are recovered (or to recovered) in the continuum limit. Both degenerate and non-degenerate mass terms are dealt with and the various U(1) invariances of the lattice actions are pointed out

Superfluid response in heavy fermion superconductors

Science.gov (United States)

Zhong, Yin; Zhang, Lan; Shao, Can; Luo, Hong-Gang

2017-10-01

Motivated by a recent London penetration depth measurement [H. Kim, et al., Phys. Rev. Lett. 114, 027003 (2015)] and novel composite pairing scenario [O. Erten, R. Flint, and P. Coleman, Phys. Rev. Lett. 114, 027002 (2015)] of the Yb-doped heavy fermion superconductor CeCoIn5, we revisit the issue of superfluid response in the microscopic heavy fermion lattice model. However, from the literature, an explicit expression for the superfluid response function in heavy fermion superconductors is rare. In this paper, we investigate the superfluid density response function in the celebrated Kondo-Heisenberg model. To be specific, we derive the corresponding formalism from an effective fermionic large- N mean-field pairing Hamiltonian whose pairing interaction is assumed to originate from the effective local antiferromagnetic exchange interaction. Interestingly, we find that the physically correct, temperature-dependent superfluid density formula can only be obtained if the external electromagnetic field is directly coupled to the heavy fermion quasi-particle rather than the bare conduction electron or local moment. Such a unique feature emphasizes the key role of the Kondo-screening-renormalized heavy quasi-particle for low-temperature/energy thermodynamics and transport behaviors. As an important application, the theoretical result is compared to an experimental measurement in heavy fermion superconductors CeCoIn5 and Yb-doped Ce1- x Yb x CoIn5 with fairly good agreement and the transition of the pairing symmetry in the latter material is explained as a simple doping effect. In addition, the requisite formalism for the commonly encountered nonmagnetic impurity and non-local electrodynamic effect are developed. Inspired by the success in explaining classic 115-series heavy fermion superconductors, we expect the present theory will be applied to understand other heavy fermion superconductors such as CeCu2Si2 and more generic multi-band superconductors.

Effect of quintessence on holographic fermionic spectrum

Energy Technology Data Exchange (ETDEWEB)

Kuang, Xiao-Mei [Yangzhou University, Center for Gravitation and Cosmology, College of Physical Science and Technology, Yangzhou (China); Pontificia Universidad Catolica de Valparaiso, Instituto de Fisica, Valparaiso (Chile); Wu, Jian-Pin [Bohai University, Institute of Gravitation and Cosmology, Department of Physics, School of Mathematics and Physics, Jinzhou (China)

2017-10-15

In this letter, we investigate the holographic fermionic spectrum without/with dipole coupling dual to the Reissner-Nordstroem anti-de Sitter (RN-AdS) black brane surrounded by quintessence. We find that the low energy excitation of this fermionic system without dipole coupling behaves as a non-Fermi liquid. In particular, the introduction of quintessence aggravates the degree of deviation from a Fermi liquid. For the system with dipole coupling, the phase transition from (non-)Fermi liquid to Mott phase can be observed. The ratio between the width of gap and the critical temperature, beyond which the gap closes, is also worked out. We find that this ratio is larger than that of the holographic fermionic system dual to the RN-AdS black brane and even the material of V O{sub 2}. It means that our holographic system with quintessence can model new phenomena of the condensed matter system and provide some new insights in their regard. (orig.)

Majorana fermion codes

International Nuclear Information System (INIS)

Bravyi, Sergey; Terhal, Barbara M; Leemhuis, Bernhard

2010-01-01

We initiate the study of Majorana fermion codes (MFCs). These codes can be viewed as extensions of Kitaev's one-dimensional (1D) model of unpaired Majorana fermions in quantum wires to higher spatial dimensions and interacting fermions. The purpose of MFCs is to protect quantum information against low-weight fermionic errors, that is, operators acting on sufficiently small subsets of fermionic modes. We examine to what extent MFCs can surpass qubit stabilizer codes in terms of their stability properties. A general construction of 2D MFCs is proposed that combines topological protection based on a macroscopic code distance with protection based on fermionic parity conservation. Finally, we use MFCs to show how to transform any qubit stabilizer code to a weakly self-dual CSS code.

Neutral kaon mixing beyond the Standard Model with nf=2+1 chiral fermions. Part 1: bare matrix elements and physical results

International Nuclear Information System (INIS)

Garron, Nicolas; Hudspith, Renwick J.; Lytle, Andrew T.

2016-01-01

We compute the hadronic matrix elements of the four-quark operators relevant for K 0 −K̄ 0 mixing beyond the Standard Model. Our results are from lattice QCD simulations with n f =2+1 flavours of domain-wall fermion, which exhibit continuum-like chiral-flavour symmetry. The simulations are performed at two different values of the lattice spacing (a∼0.08 and a∼0.11 fm) and with lightest unitary pion mass ∼300 MeV. For the first time, the full set of relevant four-quark operators is renormalised non-perturbatively through RI-SMOM schemes; a detailed description of the renormalisation procedure is presented in a companion paper. We argue that the intermediate renormalisation scheme is responsible for the discrepancies found by different collaborations. We also study different normalisations and determine the matrix elements of the relevant four-quark operators with a precision of ∼5% or better.

The investigation of the non-orthogonal basis expansion method for a three-fermion system

International Nuclear Information System (INIS)

Baoqiu Chen; Kentucky Univ., Lexington, KY

1992-01-01

In this paper, the non-orthogonal basis expansion method has been extended to solve a three-fermion system. The radial wavefunction of such a system is expanded in terms of a non-orthogonal Gaussian basis. All matrix elements of the Hamiltonian, including the central, tensor and spin-orbit potentials are derived in analytical forms. The new method simplifies the three-body system calculations, which are usually rather tedious by other methods. The method can be used to calculate energies for both the ground state and low excited states and has been used further to investigate the other nuclear properties of a three-body system such as Λ 3 H. (Author)

Unitary unified field theories

International Nuclear Information System (INIS)

Sudarshan, E.C.G.

1976-01-01

This is an informal exposition of some recent developments. Starting with an examination of the universality of electromagnetic and weak interactions, the attempts at their unification are outlined. The theory of unitary renormalizable self-coupled vector mesons with dynamical sources is formulated for a general group. With masses introduced as variable parameters it is shown that the theory so defined is indeed unitary. Diagrammatic rules are developed in terms of a chosen set of fictitious particles. A number of special examples are outlined including a theory with strongly interacting vector and axial vector mesons and weak mesons. Applications to weak interactions of strange particles is briefly outlined. (Auth.)

Adding gauge fields to Kaplan's fermions

International Nuclear Information System (INIS)

Blum, T.; Kaerkkaeinen, L.

1994-01-01

We experiment with adding dynamical gauge field to Kaplan (defect) fermions. In the case of U(1) gauge theory we use an inhomogeneous Higgs mechanism to restrict the 3d gauge dynamics to a planar 2d defect. In our simulations the 3d theory produce the correct 2d gauge dynamics. We measure fermion propagators with dynamical gauge fields. They posses the correct chiral structure. The fermions at the boundary of the support of the gauge field (waveguide) are non-chiral, and have a mass two times heavier than the chiral modes. Moreover, these modes cannot be excited by a source at the defect; implying that they are dynamically decoupled. We have also checked that the anomaly relation is fullfilled for the case of a smooth external gauge field. (orig.)

Unitary symmetry, combinatorics, and special functions

Energy Technology Data Exchange (ETDEWEB)

Louck, J.D.

1996-12-31

From 1967 to 1994, Larry Biedenham and I collaborated on 35 papers on various aspects of the general unitary group, especially its unitary irreducible representations and Wigner-Clebsch-Gordan coefficients. In our studies to unveil comprehensible structures in this subject, we discovered several nice results in special functions and combinatorics. The more important of these will be presented and their present status reviewed.

Unitary assessment of economical efficiency of the energy resources for electricity production in Romania

International Nuclear Information System (INIS)

Luca, Gheorghe

2004-01-01

In our country, within the studies, on which the development strategies of power output are based on, the assessment of the economical efficiency of the use of two main energetic resources, the fuel used in cogeneration thermal power plants and the water used in hydropower plants respectively, was made in compliance with non-unitary specific norms. In contradiction with the degree of utilization of hydroelectric resources, realized all over the world in the developed countries (80-90%) resulted that in our country, where the degree of utilization is only 40%, the use of hydroelectric potential is not yet justified from technical-economical point of view. This anomaly was determined by the cause of non-unitary assessment of the economic efficiency for the cogeneration thermo-power plants and hydropower plants. This paper presents comparatively the elements, which were to the basis of the assessment of the economic efficiency for two types of electrical power plants, and one presents a proposal in the aim to perform a unitary assessment of the economical efficiency by applying efficiently the laws in force. (author)

The Continuum Limit of Causal Fermion Systems

OpenAIRE

Finster, Felix

2016-01-01

This monograph introduces the basic concepts of the theory of causal fermion systems, a recent approach to the description of fundamental physics. The theory yields quantum mechanics, general relativity and quantum field theory as limiting cases and is therefore a candidate for a unified physical theory. From the mathematical perspective, causal fermion systems provide a general framework for describing and analyzing non-smooth geometries and "quantum geometries." The dynamics is described by...

AdS/CFT correspondence, quasinormal modes, and thermal correlators in N=4 supersymmetric Yang-Mills theory

Science.gov (United States)

Núñez, Alvaro; Starinets, Andrei O.

2003-06-01

We use the Lorentzian AdS/CFT prescription to find the poles of the retarded thermal Green’s functions of N=4 SU(N) supersymmetric Yang-Mills theory in the limit of large N and large ’t Hooft coupling. In the process, we propose a natural definition for quasinormal modes in an asymptotically AdS spacetime, with boundary conditions dictated by the AdS/CFT correspondence. The corresponding frequencies determine the dispersion laws for the quasiparticle excitations in the dual finite-temperature gauge theory. Correlation functions of operators dual to massive scalar, vector and gravitational perturbations in a five-dimensional AdS-Schwarzschild background are considered. We find asymptotic formulas for quasinormal frequencies in the massive scalar and tensor cases, and an exact expression for vector perturbations. In the long-distance, low-frequency limit we recover results of the hydrodynamic approximation to thermal Yang-Mills theory.

AdS/CFT correspondence, quasinormal modes, and thermal correlators in N=4 supersymmetric Yang-Mills theory

International Nuclear Information System (INIS)

Nunez, Alvaro; Starinets, Andrei O.

2003-01-01

We use the Lorentzian AdS/CFT prescription to find the poles of the retarded thermal Green's functions of N=4 SU(N) supersymmetric Yang-Mills theory in the limit of large N and large 't Hooft coupling. In the process, we propose a natural definition for quasinormal modes in an asymptotically AdS spacetime, with boundary conditions dictated by the AdS/CFT correspondence. The corresponding frequencies determine the dispersion laws for the quasiparticle excitations in the dual finite-temperature gauge theory. Correlation functions of operators dual to massive scalar, vector and gravitational perturbations in a five-dimensional AdS-Schwarzschild background are considered. We find asymptotic formulas for quasinormal frequencies in the massive scalar and tensor cases, and an exact expression for vector perturbations. In the long-distance, low-frequency limit we recover results of the hydrodynamic approximation to thermal Yang-Mills theory

Quasinormal modes of modified gravity (MOG) black holes

Science.gov (United States)

Manfredi, Luciano; Mureika, Jonas; Moffat, John

2018-04-01

The Quasinormal modes (QNMs) for gravitational and electromagnetic perturbations are calculated in a Scalar-Tensor-Vector (Modified Gravity) spacetime, which was initially proposed to obtain correct dynamics of galaxies and galaxy clusters without the need for dark matter. It is found that for the increasing model parameter α, both the real and imaginary parts of the QNMs decrease compared to those for a standard Schwarzschild black hole. On the other hand, when taking into account the 1 / (1 + α) mass re-scaling factor present in MOG, Im (ω) matches almost identically that of GR, while Re (ω) is higher. These results can be identified in the ringdown phase of massive compact object mergers, and are thus timely in light of the recent gravitational wave detections by LIGO.

Global unitary fixing and matrix-valued correlations in matrix models

International Nuclear Information System (INIS)

Adler, Stephen L.; Horwitz, Lawrence P.

2003-01-01

We consider the partition function for a matrix model with a global unitary invariant energy function. We show that the averages over the partition function of global unitary invariant trace polynomials of the matrix variables are the same when calculated with any choice of a global unitary fixing, while averages of such polynomials without a trace define matrix-valued correlation functions, that depend on the choice of unitary fixing. The unitary fixing is formulated within the standard Faddeev-Popov framework, in which the squared Vandermonde determinant emerges as a factor of the complete Faddeev-Popov determinant. We give the ghost representation for the FP determinant, and the corresponding BRST invariance of the unitary-fixed partition function. The formalism is relevant for deriving Ward identities obeyed by matrix-valued correlation functions

Phase transitions in the hard-core Bose-Fermi-Hubbard model at non-zero temperatures in the heavy-fermion limit

Energy Technology Data Exchange (ETDEWEB)

Stasyuk, I.V.; Krasnov, V.O., E-mail: krasnoff@icmp.lviv.ua

2017-04-15

Phase transitions at non-zero temperatures in ultracold Bose- and Fermi-particles mixture in optical lattices using the Bose-Fermi-Hubbard model in the mean field and hard-core boson approximations are investigated. The case of infinitely small fermion transfer and the repulsive on-site boson-fermion interaction is considered. The possibility of change of order (from the 2nd to the 1st one) of the phase transition to the superfluid phase in the regime of fixed values of the chemical potentials of Bose- and Fermi-particles is established. The relevant phase diagrams determining the conditions at which such a change takes place, are built.

Operator entanglement of two-qubit joint unitary operations revisited: Schmidt number approach

Energy Technology Data Exchange (ETDEWEB)

Xia, Hui-Zhi; Li, Chao; Yang, Qing; Yang, Ming, E-mail: mingyang@ahu.edu.cn [Key Laboratory of Opto-electronic Information Acquisition and Manipulation, Ministry of Education, School of Physics and Material Science, Anhui University Hefei (China); Cao, Zhuo-Liang [School of Electronic Information Engineering, Hefei Normal University (China)

2012-08-15

The operator entanglement of two-qubit joint unitary operations is revisited. The Schmidt number, an important attribute of a two-qubit unitary operation, may have connection with the entanglement measure of the unitary operator. We find that the entanglement measure of a two-qubit unitary operators is classified by the Schmidt number of the unitary operators. We also discuss the exact relation between the operator entanglement and the parameters of the unitary operator. (author)

Self-force calculations with matched expansions and quasinormal mode sums

International Nuclear Information System (INIS)

Casals, Marc; Dolan, Sam; Ottewill, Adrian C.; Wardell, Barry

2009-01-01

Accurate modeling of gravitational wave emission by extreme-mass ratio inspirals is essential for their detection by the LISA mission. A leading perturbative approach involves the calculation of the self-force acting upon the smaller orbital body. In this work, we present the first application of the Poisson-Wiseman-Anderson method of 'matched expansions' to compute the self-force acting on a point particle moving in a curved spacetime. The method employs two expansions for the Green function, which are, respectively, valid in the 'quasilocal' and 'distant past' regimes, and which may be matched together within the normal neighborhood. We perform our calculation in a static region of the spherically symmetric Nariai spacetime (dS 2 xS 2 ), in which scalar-field perturbations are governed by a radial equation with a Poeschl-Teller potential (frequently used as an approximation to the Schwarzschild radial potential) whose solutions are known in closed form. The key new ingredients in our study are (i) very high order quasilocal expansions and (ii) expansion of the distant past Green function in quasinormal modes. In combination, these tools enable a detailed study of the properties of the scalar-field Green function. We demonstrate that the Green function is singular whenever x and x ' are connected by a null geodesic, and apply asymptotic methods to determine the structure of the Green function near the null wave front. We show that the singular part of the Green function undergoes a transition each time the null wave front passes through a caustic point, following a repeating fourfold sequence δ(σ), 1/πσ, -δ(σ), -1/πσ, etc., where σ is Synge's world function. The matched-expansion method provides insight into the nonlocal properties of the self-force. We show that the self-force generated by the segment of the worldline lying outside the normal neighborhood is not negligible. We apply the matched-expansion method to compute the scalar self-force acting on

Two-loop fermionic corrections to massive Bhabha scattering

Energy Technology Data Exchange (ETDEWEB)

Actis, S.; Riemann, T. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Czakon, M. [Wuerzburg Univ. (Germany). Inst. fuer Theoretische Physik und Astrophysik]|[Institute of Nuclear Physics, NSCR DEMOKRITOS, Athens (Greece); Gluza, J. [Silesia Univ., Katowice (Poland). Inst. of Physics

2007-05-15

We evaluate the two-loop corrections to Bhabha scattering from fermion loops in the context of pure Quantum Electrodynamics. The differential cross section is expressed by a small number of Master Integrals with exact dependence on the fermion masses m{sub e}, m{sub f} and the Mandelstam invariants s, t, u. We determine the limit of fixed scattering angle and high energy, assuming the hierarchy of scales m{sup 2}{sub e}<non-fermionic contributions. As a by-product, we provide an independent check of the known electron-loop contributions. (orig.)

Fractional fermions

International Nuclear Information System (INIS)

Jackiw, R.; Massachusetts Inst. of Tech., Cambridge; Massachusetts Inst. of Tech., Cambridge

1984-01-01

The theory of fermion fractionization due to topologically generated fermion ground states is presented. Applications to one-dimensional conductors, to the MIT bag, and to the Hall effect are reviewed. (author)

Fermionic quantum critical point of spinless fermions on a honeycomb lattice

International Nuclear Information System (INIS)

Wang, Lei; Corboz, Philippe; Troyer, Matthias

2014-01-01

Spinless fermions on a honeycomb lattice provide a minimal realization of lattice Dirac fermions. Repulsive interactions between nearest neighbors drive a quantum phase transition from a Dirac semimetal to a charge-density-wave state through a fermionic quantum critical point, where the coupling of the Ising order parameter to the Dirac fermions at low energy drastically affects the quantum critical behavior. Encouraged by a recent discovery (Huffman and Chandrasekharan 2014 Phys. Rev. B 89 111101) of the absence of the fermion sign problem in this model, we study the fermionic quantum critical point using the continuous-time quantum Monte Carlo method with a worm-sampling technique. We estimate the transition point V/t=1.356(1) with the critical exponents ν=0.80(3) and η=0.302(7). Compatible results for the transition point are also obtained with infinite projected entangled-pair states. (paper)

Multiqubit Clifford groups are unitary 3-designs

Science.gov (United States)

Zhu, Huangjun

2017-12-01

Unitary t -designs are a ubiquitous tool in many research areas, including randomized benchmarking, quantum process tomography, and scrambling. Despite the intensive efforts of many researchers, little is known about unitary t -designs with t ≥3 in the literature. We show that the multiqubit Clifford group in any even prime-power dimension is not only a unitary 2-design, but also a 3-design. Moreover, it is a minimal 3-design except for dimension 4. As an immediate consequence, any orbit of pure states of the multiqubit Clifford group forms a complex projective 3-design; in particular, the set of stabilizer states forms a 3-design. In addition, our study is helpful in studying higher moments of the Clifford group, which are useful in many research areas ranging from quantum information science to signal processing. Furthermore, we reveal a surprising connection between unitary 3-designs and the physics of discrete phase spaces and thereby offer a simple explanation of why no discrete Wigner function is covariant with respect to the multiqubit Clifford group, which is of intrinsic interest in studying quantum computation.

Efficient learning algorithm for quantum perceptron unitary weights

OpenAIRE

Seow, Kok-Leong; Behrman, Elizabeth; Steck, James

2015-01-01

For the past two decades, researchers have attempted to create a Quantum Neural Network (QNN) by combining the merits of quantum computing and neural computing. In order to exploit the advantages of the two prolific fields, the QNN must meet the non-trivial task of integrating the unitary dynamics of quantum computing and the dissipative dynamics of neural computing. At the core of quantum computing and neural computing lies the qubit and perceptron, respectively. We see that past implementat...

Simulating lattice fermions by microcanonically averaging out the nonlocal dependence of the fermionic action

International Nuclear Information System (INIS)

Azcoiti, V.; Cruz, A.; Di Carlo, G.; Grillo, A.F.; Vladikas, A.

1991-01-01

We attempt to increase the efficiency of simulations of dynamical fermions on the lattice by calculating the fermionic determinant just once for all the values of the theory's gauge coupling and flavor number. Our proposal is based on the determination of an effective fermionic action by the calculation of the fermionic determinant averaged over configurations at fixed gauge energy. The feasibility of our method is justified by the observed volume dependence of the fluctuations of the logarithm of the determinant. The algorithm we have used in order to calculate the fermionic determinant, based on the determination of all the eigenvalues of the fermionic matrix at zero mass, also enables us to obtain results at any fermion mass, with a single fermionic simulation. We test the method by simulating compact lattice QED, finding good agreement with other standard calculations. New results on the phase transition of compact QED with massless fermions on 6 4 and 8 4 lattices are also presented

Fermions and link invariants

International Nuclear Information System (INIS)

Kauffman, L.; Saleur, H.

1991-01-01

Various aspects of knot theory are discussed when fermionic degrees of freedom are taken into account in the braid group representations and in the state models. It is discussed how the R matrix for the Alexander polynomial arises from the Fox differential calculus, and how it is related to the quantum group U q gl(1,1). New families of solutions of the Yang Baxter equation obtained from ''linear'' representations of the braid group and exterior algebra are investigated. State models associated with U q sl(n,m), and in the case n=m=1 a state model for the multivariable Alexander polynomial are studied. Invariants of links in solid handlebodies are considered and it is shown how the non trivial topology lifts the boson fermion degeneracy is present in S 3 . (author) 36 refs

Quasinormal Modes and Strong Cosmic Censorship

Science.gov (United States)

Cardoso, Vitor; Costa, João L.; Destounis, Kyriakos; Hintz, Peter; Jansen, Aron

2018-01-01

The fate of Cauchy horizons, such as those found inside charged black holes, is intrinsically connected to the decay of small perturbations exterior to the event horizon. As such, the validity of the strong cosmic censorship (SCC) conjecture is tied to how effectively the exterior damps fluctuations. Here, we study massless scalar fields in the exterior of Reissner-Nordström-de Sitter black holes. Their decay rates are governed by quasinormal modes of the black hole. We identify three families of modes in these spacetimes: one directly linked to the photon sphere, well described by standard WKB-type tools; another family whose existence and time scale is closely related to the de Sitter horizon; finally, a third family which dominates for near-extremally charged black holes and which is also present in asymptotically flat spacetimes. The last two families of modes seem to have gone unnoticed in the literature. We give a detailed description of linear scalar perturbations of such black holes, and conjecture that SCC is violated in the near extremal regime.

On Investigating GMRES Convergence using Unitary Matrices

Czech Academy of Sciences Publication Activity Database

Duintjer Tebbens, Jurjen; Meurant, G.; Sadok, H.; Strakoš, Z.

2014-01-01

Roč. 450, 1 June (2014), s. 83-107 ISSN 0024-3795 Grant - others:GA AV ČR(CZ) M100301201; GA MŠk(CZ) LL1202 Institutional support: RVO:67985807 Keywords : GMRES convergence * unitary matrices * unitary spectra * normal matrices * Krylov residual subspace * Schur parameters Subject RIV: BA - General Mathematics Impact factor: 0.939, year: 2014

Fermion boson metamorphosis in field theory

International Nuclear Information System (INIS)

Ha, Y.K.

1982-01-01

In two-dimensional field theories many features are especially transparent if the Fermi fields are represented by non-local expressions of the Bose fields. Such a procedure is known as boson representation. Bilinear quantities appear in the Lagrangian of a fermion theory transform, however, as simple local expressions of the bosons so that the resulting theory may be written as a theory of bosons. Conversely, a theory of bosons may be transformed into an equivalent theory of fermions. Together they provide a basis for generating many interesting equivalences between theories of different types. In the present work a consistent scheme for constructing a canonical Fermi field in terms of a real scalar field is developed and such a procedure is valid and consistent with the tenets of quantum field theory is verified. A boson formulation offers a unifying theme in understanding the structure of many theories. This is illustrated by the boson formulation of a multifermion theory with chiral and internal symmetries. The nature of dynamical generation of mass when the theory undergoes boson transmutation and the preservation of continuous chiral symmetry in the massive case are examined. The dynamics of the system depends to a great extent on the specific number of fermions and different models of the same system can have very different properties. Many unusual symmetries of the fermion theory, such as hidden symmetry, duality and triality symmetries, are only manifest in the boson formulation. The underlying connections between some models with U(N) internal symmetry and another class of fermion models built with Majorana fermions which have O(2N) internal symmetry are uncovered

Fermionic One-Way Quantum Computation

International Nuclear Information System (INIS)

Cao Xin; Shang Yun

2014-01-01

Fermions, as another major class of quantum particles, could be taken as carriers for quantum information processing beyond spins or bosons. In this work, we consider the fermionic generalization of the one-way quantum computation model and find that one-way quantum computation can also be simulated with fermions. In detail, using the n → 2n encoding scheme from a spin system to a fermion system, we introduce the fermionic cluster state, then the universal computing power with a fermionic cluster state is demonstrated explicitly. Furthermore, we show that the fermionic cluster state can be created only by measurements on at most four modes with |+〉 f (fermionic Bell state) being free

Singlets of fermionic gauge symmetries

NARCIS (Netherlands)

Bergshoeff, E.A.; Kallosh, R.E.; Rahmanov, M.A.

1989-01-01

We investigate under which conditions singlets of fermionic gauge symmetries which are "square roots of gravity" can exist. Their existence is non-trivial because there are no fields neutral in gravity. We tabulate several examples of singlets of global and local supersymmetry and κ-symmetry and

Fermionic cosmologies

International Nuclear Information System (INIS)

Chimento, L P; Forte, M; Devecchi, F P; Kremer, G M; Ribas, M O; Samojeden, L L

2011-01-01

In this work we review if fermionic sources could be responsible for accelerated periods during the evolution of a FRW universe. In a first attempt, besides the fermionic source, a matter constituent would answer for the decelerated periods. The coupled differential equations that emerge from the field equations are integrated numerically. The self-interaction potential of the fermionic field is considered as a function of the scalar and pseudo-scalar invariants. It is shown that the fermionic field could behave like an inflaton field in the early universe, giving place to a transition to a matter dominated (decelerated) period. In a second formulation we turn our attention to analytical results, specifically using the idea of form-invariance transformations. These transformations can be used for obtaining accelerated cosmologies starting with conventional cosmological models. Here we reconsider the scalar field case and extend the discussion to fermionic fields. Finally we investigate the role of a Dirac field in a Brans-Dicke (BD) context. The results show that this source, in combination with the BD scalar, promote a final eternal accelerated era, after a matter dominated period.

Light fermions in quantum gravity

International Nuclear Information System (INIS)

Eichhorn, Astrid; Gies, Holger

2011-01-01

We study the impact of quantum gravity, formulated as a quantum field theory of the metric, on chiral symmetry in a fermionic matter sector. Specifically we address the question of whether metric fluctuations can induce chiral symmetry breaking and bound state formation. Our results based on the functional renormalization group indicate that chiral symmetry is left intact even at strong gravitational coupling. In particular, we found that asymptotically safe quantum gravity where the gravitational couplings approach a non-Gaußian fixed point generically admits universes with light fermions. Our results thus further support quantum gravity theories built on fluctuations of the metric field such as the asymptotic-safety scenario. A study of chiral symmetry breaking through gravitational quantum effects may also serve as a significant benchmark test for other quantum gravity scenarios, since a completely broken chiral symmetry at the Planck scale would not be in accordance with the observation of light fermions in our universe. We demonstrate that this elementary observation already imposes constraints on a generic UV completion of gravity. (paper)

Quantum quenches in a holographic Kondo model

Science.gov (United States)

Erdmenger, Johanna; Flory, Mario; Newrzella, Max-Niklas; Strydom, Migael; Wu, Jackson M. S.

2017-04-01

We study non-equilibrium dynamics and quantum quenches in a recent gauge/gravity duality model for a strongly coupled system interacting with a magnetic impurity with SU( N ) spin. At large N , it is convenient to write the impurity spin as a bilinear in Abrikosov fermions. The model describes an RG flow triggered by the marginally relevant Kondo operator. There is a phase transition at a critical temperature, below which an operator condenses which involves both an electron and an Abrikosov fermion field. This corresponds to a holographic superconductor in AdS2 and models the impurity screening. We quench the Kondo coupling either by a Gaussian pulse or by a hyperbolic tangent, the latter taking the system from the condensed to the uncondensed phase or vice-versa. We study the time dependence of the condensate induced by this quench. The timescale for equilibration is generically given by the leading quasinormal mode of the dual gravity model. This mode also governs the formation of the screening cloud, which is obtained as the decrease of impurity degrees of freedom with time. In the condensed phase, the leading quasinormal mode is imaginary and the relaxation of the condensate is over-damped. For quenches whose final state is close to the critical point of the large N phase transition, we study the critical slowing down and obtain the combination of critical exponents zν = 1. When the final state is exactly at the phase transition, we find that the exponential ringing of the quasinormal modes is replaced by a power-law behaviour of the form ˜ t - a sin( b log t). This indicates the emergence of a discrete scale invariance.

Unitary group representations in Fock spaces with generalized exchange properties

International Nuclear Information System (INIS)

Liguori, A.

1994-09-01

The notion of second R-quantization is investigated, - a suitable deformation of the standard second quantization which properly takes into account the non-trivial exchange properties characterizing generalized statistics. The R-quantization of a class of unitary one-particle representations relevant for the description of symmetries is also performed. The Euclidean covariance of anyons is analyzed in this context. (author). 11 refs

q-deformed charged fermion coherent states and SU(3) charged, Hyper-charged fermion coherent states

International Nuclear Information System (INIS)

Hao Sanru; Li Guanghua; Long Junyan

1994-01-01

By virtue of the algebra of the q-deformed fermion oscillators, the q-deformed charged fermion coherent states and SU(3) charged, hyper-charged fermion coherent states are discussed. The explicit forms of the two kinds of coherent states mentioned above are obtained by making use of the completeness of base vectors in the q-fermion Fock space. By comparing the q-deformed results with the ordinary results, it is found that the q-deformed charged fermion coherent states and SU(3) charged, hyper-charged fermion coherent states are automatically reduced to the ordinary charged fermion coherent states and SU(3) charged hyper-charged fermion coherent states if the deformed parameter q→1

Highly damped quasinormal modes of generic single-horizon black holes

Energy Technology Data Exchange (ETDEWEB)

Daghigh, Ramin G [Physics Department, University of Winnipeg, Winnipeg, Manitoba R3B 2E9 (Canada); Kunstatter, Gabor [Winnipeg Institute for Theoretical Physics, Winnipeg, Manitoba (Canada)

2005-10-07

We calculate analytically the highly damped quasinormal mode spectra of generic single-horizon black holes using the rigorous WKB techniques of Andersson and Howls (2004 Class. Quantum Grav. 21 1623). We thereby provide a firm foundation for previous analysis, and point out some of their possible limitations. The numerical coefficient in the real part of the highly damped frequency is generically determined by the behaviour of coupling of the perturbation to the gravitational field near the origin, as expressed in tortoise coordinates. This fact makes it difficult to understand how the famous ln(3) could be related to the quantum gravitational microstates near the horizon.

Geodesic stability, Lyapunov exponents, and quasinormal modes

International Nuclear Information System (INIS)

Cardoso, Vitor; Miranda, Alex S.; Berti, Emanuele; Witek, Helvi; Zanchin, Vilson T.

2009-01-01

Geodesic motion determines important features of spacetimes. Null unstable geodesics are closely related to the appearance of compact objects to external observers and have been associated with the characteristic modes of black holes. By computing the Lyapunov exponent, which is the inverse of the instability time scale associated with this geodesic motion, we show that, in the eikonal limit, quasinormal modes of black holes in any dimensions are determined by the parameters of the circular null geodesics. This result is independent of the field equations and only assumes a stationary, spherically symmetric and asymptotically flat line element, but it does not seem to be easily extendable to anti-de Sitter spacetimes. We further show that (i) in spacetime dimensions greater than four, equatorial circular timelike geodesics in a Myers-Perry black-hole background are unstable, and (ii) the instability time scale of equatorial null geodesics in Myers-Perry spacetimes has a local minimum for spacetimes of dimension d≥6.

On relevant boundary perturbations of unitary minimal models

International Nuclear Information System (INIS)

Recknagel, A.; Roggenkamp, D.; Schomerus, V.

2000-01-01

We consider unitary Virasoro minimal models on the disk with Cardy boundary conditions and discuss deformations by certain relevant boundary operators, analogous to tachyon condensation in string theory. Concentrating on the least relevant boundary field, we can perform a perturbative analysis of renormalization group fixed points. We find that the systems always flow towards stable fixed points which admit no further (non-trivial) relevant perturbations. The new conformal boundary conditions are in general given by superpositions of 'pure' Cardy boundary conditions

Contribution to the study of non-lethal whole-body gamma irradiation effects on the unitary activities of the dorsal hippocampus in rabbits

International Nuclear Information System (INIS)

Bassant, M.-H.

1976-01-01

The effects of non-lethal whole-body gamma irradiation on the spontaneous activity of the dorsal hippocampus pyramidal cells were studied in rabbits. First of all the unitary activity of the CA 1 and CA 4 pyramidal cells was recorded extracellularly in the reference animal. The results were analyzed by a statistical method. By classifying the various cell functioning modes observed, and measuring the frequency with which they appear as a function of the state of vigilance, an attempt was made to characterize precisely the spontaneous activity of the hippocampal neurons. Recording were then made under identical experimental conditions on animals totally irradiated to mean absorbed doses of 250 and 450 rads (delivered at a constant rate of 14 rads/mn). The electroencephalographic activity of the hippocampus shows many anomalies (slow waves, wave-points, theta rythm deformation) as a function of which several pathological states were distinguished and used to classify the data, then processed by the methods already used for the reference data. The results obtained prove that the statistical characteristics of the unitary activity are changed by irradiation [fr

Non-perturbative renormalization of left-left four-fermion operators in quenched lattice QCD

CERN Document Server

Guagnelli, M; Peña, C; Sint, S; Vladikas, A

2006-01-01

We define a family of Schroedinger Functional renormalization schemes for the four-quark multiplicatively renormalizable operators of the $\\Delta F = 1$ and $\\Delta F = 2$ effective weak Hamiltonians. Using the lattice regularization with quenched Wilson quarks, we compute non-perturbatively the renormalization group running of these operators in the continuum limit in a large range of renormalization scales. Continuum limit extrapolations are well controlled thanks to the implementation of two fermionic actions (Wilson and Clover). The ratio of the renormalization group invariant operator to its renormalized counterpart at a low energy scale, as well as the renormalization constant at this scale, is obtained for all schemes.

Partition functions in even dimensional AdS via quasinormal mode methods

International Nuclear Information System (INIS)

Keeler, Cynthia; Ng, Gim Seng

2014-01-01

In this note, we calculate the one-loop determinant for a massive scalar (with conformal dimension Δ) in even-dimensional AdS d+1 space, using the quasinormal mode method developed in http://dx.doi.org/10.1088/0264-9381/27/12/125001 by Denef, Hartnoll, and Sachdev. Working first in two dimensions on the related Euclidean hyperbolic plane H 2 , we find a series of zero modes for negative real values of Δ whose presence indicates a series of poles in the one-loop partition function Z(Δ) in the Δ complex plane; these poles contribute temperature-independent terms to the thermal AdS partition function computed in http://dx.doi.org/10.1088/0264-9381/27/12/125001. Our results match those in a series of papers by Camporesi and Higuchi, as well as Gopakumar et al. http://dx.doi.org/10.1007/JHEP11(2011)010 and Banerjee et al. http://dx.doi.org/10.1007/JHEP03(2011)147. We additionally examine the meaning of these zero modes, finding that they Wick-rotate to quasinormal modes of the AdS 2 black hole. They are also interpretable as matrix elements of the discrete series representations of SO(2,1) in the space of smooth functions on S 1 . We generalize our results to general even dimensional AdS 2n , again finding a series of zero modes which are related to discrete series representations of SO(2n,1), the motion group of H 2n .

Quantum gravity and Standard-Model-like fermions

International Nuclear Information System (INIS)

Eichhorn, Astrid; Lippoldt, Stefan

2017-01-01

We discover that chiral symmetry does not act as an infrared attractor of the renormalization group flow under the impact of quantum gravity fluctuations. Thus, observationally viable quantum gravity models must respect chiral symmetry. In our truncation, asymptotically safe gravity does, as a chiral fixed point exists. A second non-chiral fixed point with massive fermions provides a template for models with dark matter. This fixed point disappears for more than 10 fermions, suggesting that an asymptotically safe ultraviolet completion for the standard model plus gravity enforces chiral symmetry.

Fermionic corrections to fluid dynamics from BTZ black hole

Energy Technology Data Exchange (ETDEWEB)

Gentile, L.G.C. [DISIT, Università del Piemonte Orientale,via T. Michel, 11, Alessandria, 15120 (Italy); Dipartimento di Fisica “Galileo Galilei”,Università di Padova, via Marzolo 8, 35131 Padova (Italy); INFN - Sezione di Padova,via Marzolo 8, 35131, Padova (Italy); Grassi, P.A. [DISIT, Università del Piemonte Orientale,via T. Michel, 11, Alessandria, 15120 (Italy); INFN - Gruppo Collegato di Alessandria, Sezione di Torino,Alessandria (Italy); PH-TH Department, CERN,CH-1211 Geneva 23 (Switzerland); Mezzalira, A. [Dipartimento di Fisica Teorica, Università di Torino,via P. Giuria, 1, Torino, 10125 (Italy); INFN - Gruppo Collegato di Alessandria, Sezione di Torino,Alessandria (Italy)

2015-11-23

We reconstruct the complete fermionic orbit of the non-extremal BTZ black hole by acting with finite supersymmetry transformations. The solution satisfies the exact supergravity equations of motion to all orders in the fermonic expansion and the final result is given in terms of fermionic bilinears. By fluid/gravity correspondence, we derive linearized Navier-Stokes equations and a set of new differential equations from Rarita-Schwinger equation. We compute the boundary energy-momentum tensor and we interpret the result as a perfect fluid with a modified definition of fluid velocity. Finally, we derive the modified expression for the entropy of the black hole in terms of the fermionic bilinears.

Fermion bag approach to the sign problem in strongly coupled lattice QED with Wilson fermions

OpenAIRE

Chandrasekharan, Shailesh; Li, Anyi

2010-01-01

We explore the sign problem in strongly coupled lattice QED with one flavor of Wilson fermions in four dimensions using the fermion bag formulation. We construct rules to compute the weight of a fermion bag and show that even though the fermions are confined into bosons, fermion bags with negative weights do exist. By classifying fermion bags as either simple or complex, we find numerical evidence that complex bags with positive and negative weights come with almost equal probabilities and th...

Confinement in (1+1) dimensions and fermions

International Nuclear Information System (INIS)

Boya, L.J.; Gomez, C.

1979-01-01

The sign ambiguity in fermions in (1+1) dimensions leads to half-integer gauge transformations and to non-zero vacuum expectation values of the physical fermi field which strongly suggest confinement. (Auth.)

Four fermion interaction near four dimensions

International Nuclear Information System (INIS)

Zinn-Justin, J.

1991-01-01

It is known that field theories with attractive four-point fermion interactions can produce scalar bound states: Fermion mass generation by spontaneous chiral symmetry breaking associated with such fermion bound states provides an attractive mechanism for building models of composite Higgs bosons. The ratio of fermion and boson masses can then be predicted while it seems to be a free parameter in similar models where a boson field explicitly appears in the action. The main problem is that the corresponding models are renormalizable only in two dimensions, in contrast with models with explicit bosons. Many fermion models with four-point interaction are asymptotically free in two dimensions and then behave also like renormalizable models in higher dimensions, at least within the framework of some 1/N expansion. On the other hand mass ratio predictions also follow in the models with explicit bosons, when they have an IR fixed point, from the additional natural assumption that coupling constants have generic values at the cut-off scale. To the model with a four fermion interaction one can associate an effective model containing an additional scalar field, renormalizable in four dimensions, which has the same large distance, small momentum physics, at least to all orders in some 1/N expansion. Even the leading corrections corresponding to irrelevant or marginal operators are identical. This property is important in four dimensions where the IR fixed point coupling constants vanish: The correction amplitudes can be varied by changing the coupling constants in the renormalizable model and the cut-off function in the perturbatively non-renormalizable model. We shall consider here for definiteness only the Gross-Neveu model but it will be clear that the arguments are more general

Fermion number in supersymmetric models

International Nuclear Information System (INIS)

Mainland, G.B.; Tanaka, K.

1975-01-01

The two known methods for introducing a conserved fermion number into supersymmetric models are discussed. While the introduction of a conserved fermion number often requires that the Lagrangian be massless or that bosons carry fermion number, a model is discussed in which masses can be introduced via spontaneous symmetry breaking and fermion number is conserved at all stages without assigning fermion number to bosons. (U.S.)

Neutral kaon mixing beyond the Standard Model with n{sub f}=2+1 chiral fermions. Part 1: bare matrix elements and physical results

Energy Technology Data Exchange (ETDEWEB)

Garron, Nicolas [Theoretical Physics Division, Department of Mathematical Sciences, University of Liverpool,Brownlow Hill, Liverpool, L69 3BX (United Kingdom); Hudspith, Renwick J. [Department of Physics and Astronomy, York University,4700 Keele Street, Toronto, Ontario, M3J 1P3 (Canada); Lytle, Andrew T. [SUPA, School of Physics and Astronomy, University of Glasgow,University Avenue, Glasgow, G12 8QQ (United Kingdom); Collaboration: The RBC/UKQCD collaboration

2016-11-02

We compute the hadronic matrix elements of the four-quark operators relevant for K{sup 0}−K̄{sup 0} mixing beyond the Standard Model. Our results are from lattice QCD simulations with n{sub f}=2+1 flavours of domain-wall fermion, which exhibit continuum-like chiral-flavour symmetry. The simulations are performed at two different values of the lattice spacing (a∼0.08 and a∼0.11 fm) and with lightest unitary pion mass ∼300 MeV. For the first time, the full set of relevant four-quark operators is renormalised non-perturbatively through RI-SMOM schemes; a detailed description of the renormalisation procedure is presented in a companion paper. We argue that the intermediate renormalisation scheme is responsible for the discrepancies found by different collaborations. We also study different normalisations and determine the matrix elements of the relevant four-quark operators with a precision of ∼5% or better.

A Class of Hamiltonians for a Three-Particle Fermionic System at Unitarity

Energy Technology Data Exchange (ETDEWEB)

Correggi, M., E-mail: michele.correggi@gmail.com [Università degli Studi Roma Tre, Largo San Leonardo Murialdo 1, Dipartimento di Matematica e Fisica (Italy); Dell’Antonio, G. [“Sapienza” Università di Roma, P.le A. Moro 5, Dipartimento di Matematica (Italy); Finco, D. [Università Telematica Internazionale Uninettuno, Corso V. Emanuele II 39, Facoltà di Ingegneria (Italy); Michelangeli, A. [Scuola Internazionale Superiore di Studi Avanzati, Via Bonomea 265 (Italy); Teta, A. [“Sapienza” Università di Roma, P.le A. Moro 5, Dipartimento di Matematica (Italy)

2015-12-15

We consider a quantum mechanical three-particle system made of two identical fermions of mass one and a different particle of mass m, where each fermion interacts via a zero-range force with the different particle. In particular we study the unitary regime, i.e., the case of infinite two-body scattering length. The Hamiltonians describing the system are, by definition, self-adjoint extensions of the free Hamiltonian restricted on smooth functions vanishing at the two-body coincidence planes, i.e., where the positions of two interacting particles coincide. It is known that for m larger than a critical value m{sup ∗} ≃ (13.607){sup −1} a self-adjoint and lower bounded Hamiltonian H{sub 0} can be constructed, whose domain is characterized in terms of the standard point-interaction boundary condition at each coincidence plane. Here we prove that for m ∈ (m{sup ∗},m{sup ∗∗}), where m{sup ∗∗} ≃ (8.62){sup −1}, there is a further family of self-adjoint and lower bounded Hamiltonians H{sub 0,β}, β ∈ ℝ, describing the system. Using a quadratic form method, we give a rigorous construction of such Hamiltonians and we show that the elements of their domains satisfy a further boundary condition, characterizing the singular behavior when the positions of all the three particles coincide.

A Class of Hamiltonians for a Three-Particle Fermionic System at Unitarity

International Nuclear Information System (INIS)

Correggi, M.; Dell’Antonio, G.; Finco, D.; Michelangeli, A.; Teta, A.

2015-01-01

We consider a quantum mechanical three-particle system made of two identical fermions of mass one and a different particle of mass m, where each fermion interacts via a zero-range force with the different particle. In particular we study the unitary regime, i.e., the case of infinite two-body scattering length. The Hamiltonians describing the system are, by definition, self-adjoint extensions of the free Hamiltonian restricted on smooth functions vanishing at the two-body coincidence planes, i.e., where the positions of two interacting particles coincide. It is known that for m larger than a critical value m ∗ ≃ (13.607) −1 a self-adjoint and lower bounded Hamiltonian H 0 can be constructed, whose domain is characterized in terms of the standard point-interaction boundary condition at each coincidence plane. Here we prove that for m ∈ (m ∗ ,m ∗∗ ), where m ∗∗ ≃ (8.62) −1 , there is a further family of self-adjoint and lower bounded Hamiltonians H 0,β , β ∈ ℝ, describing the system. Using a quadratic form method, we give a rigorous construction of such Hamiltonians and we show that the elements of their domains satisfy a further boundary condition, characterizing the singular behavior when the positions of all the three particles coincide

Unitary Transformations in 3 D Vector Representation of Qutrit States

Science.gov (United States)

2018-03-12

ARL-TR-8330 ● MAR 2018 US Army Research Laboratory Unitary Transformations in 3- D Vector Representation of Qutrit States by...return it to the originator. ARL-TR-8330 ● MAR 2018 US Army Research Laboratory Unitary Transformations in 3- D Vector...2018 2. REPORT TYPE Technical Report 3. DATES COVERED June–December 2017 4. TITLE AND SUBTITLE Unitary Transformations in 3- D Vector

Scaling behavior of heavy fermion metals

Energy Technology Data Exchange (ETDEWEB)

Shaginyan, V.R., E-mail: vrshag@thd.pnpi.spb.r [Petersburg Nuclear Physics Institute, RAS, Gatchina, 188300 (Russian Federation); CTSPS, Clark Atlanta University, Atlanta, GA 30314 (United States); Amusia, M.Ya. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Ioffe Physical Technical Institute, RAS, St. Petersburg 194021 (Russian Federation); Msezane, A.Z. [CTSPS, Clark Atlanta University, Atlanta, GA 30314 (United States); Popov, K.G. [Komi Science Center, Ural Division, RAS, 3a, Chernova str. Syktyvkar, 167982 (Russian Federation)

2010-07-15

Strongly correlated Fermi systems are fundamental systems in physics that are best studied experimentally, which until very recently have lacked theoretical explanations. This review discusses the construction of a theory and the analysis of phenomena occurring in strongly correlated Fermi systems such as heavy-fermion (HF) metals and two-dimensional (2D) Fermi systems. It is shown that the basic properties and the scaling behavior of HF metals can be described within the framework of a fermion condensation quantum phase transition (FCQPT) and an extended quasiparticle paradigm that allow us to explain the non-Fermi liquid behavior observed in strongly correlated Fermi systems. In contrast to the Landau paradigm stating that the quasiparticle effective mass is a constant, the effective mass of new quasiparticles strongly depends on temperature, magnetic field, pressure, and other parameters. Having analyzed the collected facts on strongly correlated Fermi systems with quite a different microscopic nature, we find these to exhibit the same non-Fermi liquid behavior at FCQPT. We show both analytically and using arguments based entirely on the experimental grounds that the data collected on very different strongly correlated Fermi systems have a universal scaling behavior, and materials with strongly correlated fermions can unexpectedly be uniform in their diversity. Our analysis of strongly correlated systems such as HF metals and 2D Fermi systems is in the context of salient experimental results. Our calculations of the non-Fermi liquid behavior, the scales and thermodynamic, relaxation and transport properties are in good agreement with experimental facts.

Unitary W-algebras and three-dimensional higher spin gravities with spin one symmetry

International Nuclear Information System (INIS)

Afshar, Hamid; Creutzig, Thomas; Grumiller, Daniel; Hikida, Yasuaki; Rønne, Peter B.

2014-01-01

We investigate whether there are unitary families of W-algebras with spin one fields in the natural example of the Feigin-Semikhatov W_n"("2")-algebra. This algebra is conjecturally a quantum Hamiltonian reduction corresponding to a non-principal nilpotent element. We conjecture that this algebra admits a unitary real form for even n. Our main result is that this conjecture is consistent with the known part of the operator product algebra, and especially it is true for n=2 and n=4. Moreover, we find certain ranges of allowed levels where a positive definite inner product is possible. We also find a unitary conformal field theory for every even n at the special level k+n=(n+1)/(n−1). At these points, the W_n"("2")-algebra is nothing but a compactified free boson. This family of W-algebras admits an ’t Hooft limit. Further, in the case of n=4, we reproduce the algebra from the higher spin gravity point of view. In general, gravity computations allow us to reproduce some leading coefficients of the operator product.

Blockspin and multigrid for staggered fermions in non-abelian gauge fields

International Nuclear Information System (INIS)

Kalkreuter, T.; Mack, G.; Speh, M.

1991-07-01

We discuss blockspins for staggered fermions, i.e. averaging and interpolation procedures which are needed in a real space renormalization group approach to gauge theories with staggered fermions and in a multigrid approach to the computation of gauge covariant propagators. The discussion starts from the requirement that the symmetries of the free action should be preserved by the blocking procedure in the limit of a pure gauge. A definition of an averaging kernel as a solution of a gauge covariant eigenvalue equation is proposed, and the properties of a corresponding interpolation kernel are examined in the light of general criteria for good choices of blockspins. Some results of multigrid computation of bosonic propagation in an SU(2) gauge field in 4 dimensions are also presented. (orig.)

AdS/CFT correspondence, quasinormal modes, and thermal correlators in N=4 SYM

OpenAIRE

Nunez, Alvaro; Starinets, Andrei O.

2003-01-01

We use the Lorentzian AdS/CFT prescription to find the poles of the retarded thermal Green's functions of ${\\cal N=4}$ SU(N) SYM theory in the limit of large N and large 't Hooft coupling. In the process, we propose a natural definition for quasinormal modes in an asymptotically AdS spacetime, with boundary conditions dictated by the AdS/CFT correspondence. The corresponding frequencies determine the dispersion laws for the quasiparticle excitations in the dual finite-temperature gauge theory...

Scaled lattice fermion fields, stability bounds, and regularity

Science.gov (United States)

O'Carroll, Michael; Faria da Veiga, Paulo A.

2018-02-01

We consider locally gauge-invariant lattice quantum field theory models with locally scaled Wilson-Fermi fields in d = 1, 2, 3, 4 spacetime dimensions. The use of scaled fermions preserves Osterwalder-Seiler positivity and the spectral content of the models (the decay rates of correlations are unchanged in the infinite lattice). In addition, it also results in less singular, more regular behavior in the continuum limit. Precisely, we treat general fermionic gauge and purely fermionic lattice models in an imaginary-time functional integral formulation. Starting with a hypercubic finite lattice Λ ⊂(aZ ) d, a ∈ (0, 1], and considering the partition function of non-Abelian and Abelian gauge models (the free fermion case is included) neglecting the pure gauge interactions, we obtain stability bounds uniformly in the lattice spacing a ∈ (0, 1]. These bounds imply, at least in the subsequential sense, the existence of the thermodynamic (Λ ↗ (aZ ) d) and the continuum (a ↘ 0) limits. Specializing to the U(1) gauge group, the known non-intersecting loop expansion for the d = 2 partition function is extended to d = 3 and the thermodynamic limit of the free energy is shown to exist with a bound independent of a ∈ (0, 1]. In the case of scaled free Fermi fields (corresponding to a trivial gauge group with only the identity element), spectral representations are obtained for the partition function, free energy, and correlations. The thermodynamic and continuum limits of the free fermion free energy are shown to exist. The thermodynamic limit of n-point correlations also exist with bounds independent of the point locations and a ∈ (0, 1], and with no n! dependence. Also, a time-zero Hilbert-Fock space is constructed, as well as time-zero, spatially pointwise scaled fermion creation operators which are shown to be norm bounded uniformly in a ∈ (0, 1]. The use of our scaled fields since the beginning allows us to extract and isolate the singularities of the free

Derivation of mean-field dynamics for fermions

International Nuclear Information System (INIS)

Petrat, Soeren

2014-01-01

In this work, we derive the time-dependent Hartree(-Fock) equations as an effective dynamics for fermionic many-particle systems. Our main results are the first for a quantum mechanical mean-field dynamics for fermions; in previous works, the mean-field limit is usually either coupled to a semiclassical limit, or the interaction is scaled down so much, that the system behaves freely for large particle number N. We mainly consider systems with total kinetic energy bounded by const.N and long-range interaction potentials, e.g., Coulomb interaction. Examples for such systems are large molecules or certain solid states. Our analysis also applies to attractive interactions, as, e.g., in fermionic stars. The fermionic Hartree(-Fock) equations are a standard tool to describe, e.g., excited states or chemical reactions of large molecules (like proteins). A deeper understanding of these equations as an approximation to the time evolution of a many body quantum system is thus highly relevant. We consider the fermionic Hartree equations (i.e., the Hartree-Fock equations without exchange term) in this work, since the exchange term is subleading in our setting. The main result is that the fermionic Hartree dynamics approximates the Schroedinger dynamics well for large N. This statement becomes exact in the thermodynamic limit N→∞. We give explicit values for the rates of convergence. We prove two types of results. The first type is very general and concerns arbitrary free Hamiltonians (e.g., relativistic, non-relativistic, with external fields) and arbitrary interactions. The theorems give explicit conditions on the solutions to the fermionic Hartree equations under which a derivation of the mean-field dynamics succeeds. The second type of results scrutinizes situations where the conditions are fulfilled. These results are about non-relativistic free Hamiltonians with external fields, systems with total kinetic energy bounded by const.N and with long-range interactions of

Probabilistic implementation of Hadamard and unitary gates

International Nuclear Information System (INIS)

Song Wei; Yang Ming; Cao Zhuoliang

2004-01-01

We show that the Hadamard and unitary gates could be implemented by a unitary evolution together with a measurement for any unknown state chosen from a set A={ vertical bar Ψi>, vertical bar Ψ-bar i>} (i=1,2) if and only if vertical bar Ψ1>, vertical bar Ψ2>, vertical bar Ψ-bar 1>, vertical bar Ψ-bar 2> are linearly independent. We also derive the best transformation efficiencies

Results form 2+1 flavours of SLiNC fermions

International Nuclear Information System (INIS)

Bietenholz, W.; Cundy, N.

2009-10-01

QCD results are presented for a 2+1 flavour fermion clover action (which we call the SLiNC action). A method of tuning the quark masses to their physical values is discussed. In this method the singlet quark mass is kept fixed, which solves the problem of different renormalisations (for singlet and non-singlet quark masses) occuring for non-chirally invariant lattice fermions. This procedure enables a wide range of quark masses to be probed, including the case with a heavy up-down quark mass and light strange quark mass. Preliminary results show the correct splittings for the baryon (octet and) decuplet spectrum. (orig.)

Minimally doubled fermions and spontaneous chiral symmetry breaking

Directory of Open Access Journals (Sweden)

Osmanaj (Zeqirllari Rudina

2018-01-01

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

Minimally doubled fermions and spontaneous chiral symmetry breaking

Science.gov (United States)

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

2018-03-01

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

Quasinormal modes of four-dimensional topological nonlinear charged Lifshitz black holes

Energy Technology Data Exchange (ETDEWEB)

Becar, Ramon [Universidad Cato lica de Temuco, Departamento de Ciencias Matematicas y Fisicas, Temuco (Chile); Gonzalez, P.A. [Universidad Diego Portales, Facultad de Ingenieria, Santiago (Chile); Vasquez, Yerko [Universidad de La Serena, Departamento de Fisica, Facultad de Ciencias, La Serena (Chile)

2016-02-15

We study scalar perturbations of four- dimensional topological nonlinear charged Lifshitz black holes with spherical and plane transverse sections, and we find numerically the quasinormal modes for scalar fields. Then we study the stability of these black holes under massive and massless scalar field perturbations. We focus our study on the dependence of the dynamical exponent, the nonlinear exponent, the angular momentum, and the mass of the scalar field in the modes. It is found that the modes are overdamped, depending strongly on the dynamical exponent and the angular momentum of the scalar field for a spherical transverse section. In contrast, for plane transverse sections the modes are always overdamped. (orig.)

Unitary representations of basic classical Lie superalgebras

International Nuclear Information System (INIS)

Gould, M.D.; Zhang, R.B.

1990-01-01

We have obtained all the finite-dimensional unitary irreps of gl(mvertical stroken) and C(n), which also exhaust such irreps of all the basic classical Lie superalgebras. The lowest weights of such irreps are worked out explicitly. It is also shown that the contravariant and covariant tensor irreps of gl(mvertical stroken) are unitary irreps of type (1) and type (2) respectively, explaining the applicability of the Young diagram method to these two types of tensor irreps. (orig.)

Superstrings fermionic solutions

International Nuclear Information System (INIS)

Rausch de Traubenberg, M.

1990-06-01

The solutions proposed by the superstring theory are classified and compared. In order to obtain some of the equivalences, the demonstration is based on the coincidence of the excitation spectrum and the quantum numbers from different states. The fermionic representation of the heterotical strings is discussed. The conformal invariance and the supersymmetric results extended to two dimensions are investigated. Concerning the fermionic strings, the formalism and a phenomenological solution involving three families of quarks, chiral leptons and leptons from the E 6 gauge group are presented. The equivalence between real and complex fermions is discussed. The similarity between some of the solutions of the Wess-Zumino-Witten model and the orbifolds is considered. The formal calculation program developed for reproducing the theory's low energy spectra, in the fermionic string formalism is given [fr

Bosonic construction of the Lie algebras of some non-compact groups appearing in supergravity theories and their oscillator-like unitary representations

International Nuclear Information System (INIS)

Guenaydin, M.; Saclioglu, C.

1981-06-01

We give a construction of the Lie algebras of the non-compact groups appearing in four dimensional supergravity theories in terms of boson operators. Our construction parallels very closely their emergence in supergravity and is an extension of the well-known construction of the Lie algebras of the non-compact groups Sp(2n,IR) and SO(2n) from boson operators transforming like a fundamental representation of their maximal compact subgroup U(n). However this extension is non-trivial only for n >= 4 and stops at n = 8 leading to the Lie algebras of SU(4) x SU(1,1), SU(5,1), SO(12) and Esub(7(7)). We then give a general construction of an infinite class of unitary irreducible representations of the respective non-compact groups (except for Esub(7(7)) and SO(12) obtained from the extended construction). We illustrate our construction with the examples of SU(5,1) and SO(12). (orig.)

Path representation of su-hat (2){sub k} states II: Operator construction of the fermionic character and spin-1/2 -RSOS factorization

Energy Technology Data Exchange (ETDEWEB)

Lamy-Poirier, Joel, E-mail: jlamypoirier@perimeterinstitute.c [Departement de Physique, de Genie Physique et d' Optique, Universite Laval, Quebec, Canada, G1V 0A6 (Canada); Mathieu, Pierre, E-mail: pmathieu@phy.ulaval.c [Departement de Physique, de Genie Physique et d' Optique, Universite Laval, Quebec, Canada, G1V 0A6 (Canada)

2011-06-01

This is the second of two articles (independent of each other) devoted to the analysis of the path description of the states in su-hat (2){sub k} WZW models. Here we present a constructive derivation of the fermionic character at level k based on these paths. The starting point is the expression of a path in terms of a sequence of nonlocal (formal) operators acting on the vacuum ground-state path. Within this framework, the key step is the construction of the level-k operator sequences out of those at level-1 by the action of a new type of operators. These actions of operators on operators turn out to have a path interpretation: these paths are precisely the finitized RSOS paths related to the unitary minimal models M(k+1,k+2). We thus unravel - at the level of the path representation of the states - a direct factorization into a k=1 spinon part times a RSOS factor. It is also pointed out that since there are two fermionic forms describing these finite RSOS paths, the resulting fermionic su-hat (2){sub k} characters arise in two versions. Finally, the relation between the present construction and the Nagoya spectral decomposition of the path space is sketched.

Effective Lagrangian approach to the fermion mass problem

International Nuclear Information System (INIS)

Shaw, D.S.; Volkas, R.R.

1994-01-01

An effective theory is proposed, combining the standard gauge group SU(3) C direct-product SU(2) L direct-product U(1) Y with a horizontal discrete symmetry. By assigning appropriate charges under this discrete symmetry to the various fermion fields and to (at least) two Higgs doublets, the broad spread of the fermion mass and mixing angle spectrum can be explained as a result of suppressed, non-renormalizable terms. A particular model is constructed which achieves the above while simultaneously suppressing neutral Higgs-induced flavour-changing processes. 9 refs., 3 tabs., 1 fig

Fermion-fermion scattering in quantum field theory with superconducting circuits.

Science.gov (United States)

García-Álvarez, L; Casanova, J; Mezzacapo, A; Egusquiza, I L; Lamata, L; Romero, G; Solano, E

2015-02-20

We propose an analog-digital quantum simulation of fermion-fermion scattering mediated by a continuum of bosonic modes within a circuit quantum electrodynamics scenario. This quantum technology naturally provides strong coupling of superconducting qubits with a continuum of electromagnetic modes in an open transmission line. In this way, we propose qubits to efficiently simulate fermionic modes via digital techniques, while we consider the continuum complexity of an open transmission line to simulate the continuum complexity of bosonic modes in quantum field theories. Therefore, we believe that the complexity-simulating-complexity concept should become a leading paradigm in any effort towards scalable quantum simulations.

Quantum quenches in a holographic Kondo model

Energy Technology Data Exchange (ETDEWEB)

Erdmenger, Johanna [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, 80805, Munich (Germany); Institut für Theoretische Physik und Astrophysik, Julius-Maximilians-Universität Würzburg,Am Hubland, 97074 Würzburg (Germany); Flory, Mario [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, 80805, Munich (Germany); Institute of Physics, Jagiellonian University,Łojasiewicza 11, 30-348 Kraków (Poland); Newrzella, Max-Niklas; Strydom, Migael [Max-Planck-Institut für Physik (Werner-Heisenberg-Institut),Föhringer Ring 6, 80805, Munich (Germany); Wu, Jackson M. S. [Department of Physics and Astronomy, University of Alabama,Tuscaloosa, AL 35487 (United States)

2017-04-10

We study non-equilibrium dynamics and quantum quenches in a recent gauge/ gravity duality model for a strongly coupled system interacting with a magnetic impurity with SU(N) spin. At large N, it is convenient to write the impurity spin as a bilinear in Abrikosov fermions. The model describes an RG flow triggered by the marginally relevant Kondo operator. There is a phase transition at a critical temperature, below which an operator condenses which involves both an electron and an Abrikosov fermion field. This corresponds to a holographic superconductor in AdS{sub 2} and models the impurity screening. We quench the Kondo coupling either by a Gaussian pulse or by a hyperbolic tangent, the latter taking the system from the condensed to the uncondensed phase or vice-versa. We study the time dependence of the condensate induced by this quench. The timescale for equilibration is generically given by the leading quasinormal mode of the dual gravity model. This mode also governs the formation of the screening cloud, which is obtained as the decrease of impurity degrees of freedom with time. In the condensed phase, the leading quasinormal mode is imaginary and the relaxation of the condensate is over-damped. For quenches whose final state is close to the critical point of the large N phase transition, we study the critical slowing down and obtain the combination of critical exponents zν=1. When the final state is exactly at the phase transition, we find that the exponential ringing of the quasinormal modes is replaced by a power-law behaviour of the form ∼t{sup −a}sin (blog t). This indicates the emergence of a discrete scale invariance.

Preparing and probing atomic Majorana fermions and topological order in optical lattices

International Nuclear Information System (INIS)

Kraus, C V; Diehl, S; Zoller, P; Baranov, M A

2012-01-01

We introduce a one-dimensional system of fermionic atoms in an optical lattice whose phase diagram includes topological states of different symmetry classes with a simple possibility to switch between them. The states and topological phase transitions between them can be identified by looking at their zero-energy edge modes which are Majorana fermions. We propose several universal methods of detecting the Majorana edge states, based on their genuine features: the zero-energy, localized character of the wave functions and the induced non-local fermionic correlations. (paper)

Massive Vector Fields in Rotating Black-Hole Spacetimes: Separability and Quasinormal Modes.

Science.gov (United States)

Frolov, Valeri P; Krtouš, Pavel; Kubizňák, David; Santos, Jorge E

2018-06-08

We demonstrate the separability of the massive vector (Proca) field equation in general Kerr-NUT-AdS black-hole spacetimes in any number of dimensions, filling a long-standing gap in the literature. The obtained separated equations are studied in more detail for the four-dimensional Kerr geometry and the corresponding quasinormal modes are calculated. Two of the three independent polarizations of the Proca field are shown to emerge from the separation ansatz and the results are found in an excellent agreement with those of the recent numerical study where the full coupled partial differential equations were tackled without using the separability property.

Grassmann phase space methods for fermions. II. Field theory

Energy Technology Data Exchange (ETDEWEB)

Dalton, B.J., E-mail: bdalton@swin.edu.au [Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne, Victoria 3122 (Australia); Jeffers, J. [Department of Physics, University of Strathclyde, Glasgow G4ONG (United Kingdom); Barnett, S.M. [School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

2017-02-15

In both quantum optics and cold atom physics, the behaviour of bosonic photons and atoms is often treated using phase space methods, where mode annihilation and creation operators are represented by c-number phase space variables, with the density operator equivalent to a distribution function of these variables. The anti-commutation rules for fermion annihilation, creation operators suggests the possibility of using anti-commuting Grassmann variables to represent these operators. However, in spite of the seminal work by Cahill and Glauber and a few applications, the use of Grassmann phase space methods in quantum-atom optics to treat fermionic systems is rather rare, though fermion coherent states using Grassmann variables are widely used in particle physics. This paper presents a phase space theory for fermion systems based on distribution functionals, which replace the density operator and involve Grassmann fields representing anti-commuting fermion field annihilation, creation operators. It is an extension of a previous phase space theory paper for fermions (Paper I) based on separate modes, in which the density operator is replaced by a distribution function depending on Grassmann phase space variables which represent the mode annihilation and creation operators. This further development of the theory is important for the situation when large numbers of fermions are involved, resulting in too many modes to treat separately. Here Grassmann fields, distribution functionals, functional Fokker–Planck equations and Ito stochastic field equations are involved. Typical applications to a trapped Fermi gas of interacting spin 1/2 fermionic atoms and to multi-component Fermi gases with non-zero range interactions are presented, showing that the Ito stochastic field equations are local in these cases. For the spin 1/2 case we also show how simple solutions can be obtained both for the untrapped case and for an optical lattice trapping potential.

Grassmann phase space methods for fermions. II. Field theory

International Nuclear Information System (INIS)

Dalton, B.J.; Jeffers, J.; Barnett, S.M.

2017-01-01

In both quantum optics and cold atom physics, the behaviour of bosonic photons and atoms is often treated using phase space methods, where mode annihilation and creation operators are represented by c-number phase space variables, with the density operator equivalent to a distribution function of these variables. The anti-commutation rules for fermion annihilation, creation operators suggests the possibility of using anti-commuting Grassmann variables to represent these operators. However, in spite of the seminal work by Cahill and Glauber and a few applications, the use of Grassmann phase space methods in quantum-atom optics to treat fermionic systems is rather rare, though fermion coherent states using Grassmann variables are widely used in particle physics. This paper presents a phase space theory for fermion systems based on distribution functionals, which replace the density operator and involve Grassmann fields representing anti-commuting fermion field annihilation, creation operators. It is an extension of a previous phase space theory paper for fermions (Paper I) based on separate modes, in which the density operator is replaced by a distribution function depending on Grassmann phase space variables which represent the mode annihilation and creation operators. This further development of the theory is important for the situation when large numbers of fermions are involved, resulting in too many modes to treat separately. Here Grassmann fields, distribution functionals, functional Fokker–Planck equations and Ito stochastic field equations are involved. Typical applications to a trapped Fermi gas of interacting spin 1/2 fermionic atoms and to multi-component Fermi gases with non-zero range interactions are presented, showing that the Ito stochastic field equations are local in these cases. For the spin 1/2 case we also show how simple solutions can be obtained both for the untrapped case and for an optical lattice trapping potential.

High overtones of Schwarzschild-de-Sitter quasinormal spectrum

International Nuclear Information System (INIS)

Konoplya, R.A.; Zhidenko, A.

2004-01-01

We find the high overtones of gravitational and electromagnetic quasinormal spectrum of the Schwarzschild-de Sitter black hole. The calculations show that the real parts of the electromagnetic modes asymptotically approach zero. The gravitational modes show more peculiar behavior at large n: the real part oscillates as a function of imaginary even for very high overtones and these oscillations settles to some 'profile' which just repeats itself with further increasing of the overtone number n. This lets us judge that Reω is not a constant as n →∞ but rather some oscillating function. The spacing for imaginary part Imω n+1 -Imω n for electromagnetic perturbations at high n slowly approach k e as n→∞, where k e is the surface gravity. In addition we find the lower QN modes for which the values obtained with numerical methods are in a very good agreement with those obtained through the 6th order WKB technique. (author)

Theory of the unitary representations of compact groups

International Nuclear Information System (INIS)

Burzynski, A.; Burzynska, M.

1979-01-01

An introduction contains some basic notions used in group theory, Lie group, Lie algebras and unitary representations. Then we are dealing with compact groups. For these groups we show the problem of reduction of unitary representation of Wigner's projection operators, Clebsch-Gordan coefficients and Wigner-Eckart theorem. We show (this is a new approach) the representations reduction formalism by using superoperators in Hilbert-Schmidt space. (author)

Unitary Housing Regimes in Transition

DEFF Research Database (Denmark)

Bengtsson, Bo; Jensen, Lotte

2013-01-01

Path dependence is strong in housing institutions and policy. In both Denmark and Sweden, today’s universal and ‘unitary’ (Kemeny) housing regimes can be traced back to institutions that were introduced fifty years back in history or more. Recently, universal and unitary housing systems...... in Scandinavia, and elsewhere, are under challenge from strong political and economic forces. These challenges can be summarized as economic cutbacks, privatization and Europeanization. Although both the Danish and the Swedish housing system are universal and unitary in character, they differ considerably...... in institutional detail. Both systems have corporatist features, however in Denmark public housing is based on local tenant democracy and control, and in Sweden on companies owned and controlled by the municipalities, combined with a centralized system of rent negotiations. In the paper the present challenges...

Fermions in noncommutative emergent gravity

International Nuclear Information System (INIS)

Klammer, D.

2010-01-01

Noncommutative emergent gravity is a novel framework disclosing how gravity is contained naturally in noncommutative gauge theory formulated as a matrix model. It describes a dynamical space-time which itself is a four-dimensional brane embedded in a higher-dimensional space. In noncommutative emergent gravity, the metric is not a fundamental object of the model; rather it is determined by the Poisson structure and by the induced metric of the embedding. In this work the coupling of fermions to these matrix models is studied from the point of view of noncommutative emergent gravity. The matrix Dirac operator as given by the IKKT matrix model defines an appropriate coupling for fermions to an effective gravitational metric of noncommutative four-dimensional spaces that are embedded into a ten-dimensional ambient space. As it turns out this coupling is non-standard due to a spin connection that vanishes in the preferred but unobservable coordinates defined by the model. The purpose of this work is to study the one-loop effective action of this approach. Standard results of the literature cannot be applied due to this special coupling of the fermions. However, integrating out these fields in a nontrivial geometrical background induces indeed the Einstein-Hilbert action of the effective metric, as well as additional terms which couple the noncommutative structure to the Riemann tensor, and a dilaton-like term. It remains to be understood what the effects of these terms are and whether they can be avoided. In a second step, the existence of a duality between noncommutative gauge theory and gravity which explains the phenomenon of UV/IR mixing as a gravitational effect is discussed. We show how the gravitational coupling of fermions can be interpreted as a coupling of fermions to gauge fields, which suffers then from UV/IR mixing. This explanation does not render the model finite but it reveals why some UV/IR mixing remains even in supersymmetric models, except in the N

Lattice degeneracies of fermions

International Nuclear Information System (INIS)

Raszillier, H.

1983-10-01

We present a detailed description of the minimal degeneracies of geometric (Kaehler) fermions on all the lattices of maximal symmetries in n = 1, ..., 4 dimensions. We also determine the isolated orbits of the maximal symmetry groups, which are related to the minimal numbers of ''naive'' fermions on the reciprocals of these lattices. It turns out that on the self-reciprocal lattices the minimal numbers of naive fermions are equal to the minimal numbers of degrees of freedom of geometric fermions. The description we give relies on the close connection of the maximal lattice symmetry groups with (affine) Weyl groups of root systems of (semi-) simple Lie algebras. (orig.)

Fermion bag solutions to some sign problems in four-fermion field theories

International Nuclear Information System (INIS)

Li, Anyi

2013-01-01

Lattice four-fermion models containing N flavors of staggered fermions, that are invariant under Z 2 and U(1) chiral symmetries, are known to suffer from sign problems when formulated using the auxiliary field approach. Although these problems have been ignored in previous studies, they can be severe. In this talk, we show that the sign problems disappear when the models are formulated in the fermion bag approach, allowing us to solve them rigorously for the first time.

Fermion bag solutions to some sign problems in four-fermion field theories

Science.gov (United States)

Li, Anyi

2013-04-01

Lattice four-fermion models containing N flavors of staggered fermions, that are invariant under Z2 and U(1) chiral symmetries, are known to suffer from sign problems when formulated using the auxiliary field approach. Although these problems have been ignored in previous studies, they can be severe. In this talk, we show that the sign problems disappear when the models are formulated in the fermion bag approach, allowing us to solve them rigorously for the first time.

Random walks and a simple chirally invariant lattice Hamiltonian without fermion doubling

International Nuclear Information System (INIS)

Belyea, C.I.

1992-01-01

It is shown that there is a simple chirally-invariant lattice Hamiltonian for fermions which is doubling-free but non-Hermitian and which may be valuable in lattice Hamiltonian studies of quantum chromodynamics. A connection is established between the existence of random walk representations of spinor propagators and this doubling-free formulation, in analogy with Wilson fermions. 15 refs

Fermion determinants in lattice QCD

International Nuclear Information System (INIS)

Johnson, Christopher Andrew

2001-01-01

The main topic of this thesis concerns efficient algorithms for the calculation of determinants of the kind of matrix typically encountered in lattice QCD. In particular an efficient method for calculating the fermion determinant is described. Such a calculation is useful to illustrate the effects of light dynamical (virtual) quarks. The methods employed in this thesis are stochastic methods, based on the Lanczos algorithm, which is used for the solution of large, sparse matrix problems via a partial tridiagonalisation of the matrix. Here an implementation is explored which requires less exhaustive treatment of the matrix than previous Lanczos methods. This technique exploits the analogy between the Lanczos tridiagonalisation algorithm and Gaussian quadrature in order to calculate the fermion determinant. A technique for determining a number of the eigenvalues of the matrix is also presented. A demonstration is then given of how one can improve upon this estimate considerably using variance reduction techniques, reducing the variance by a factor of order 100 with a further, equal amount of work. The variance reduction method is a two-stage process, involving a Chebyshev approximation to the quantity in question and then the subtraction of traceless operators. The method is applied to the fermion determinant for non-perturbatively improved Wilson fermions on a 16 3 x 32 lattice. It is also applicable to a wider class of matrix operators. Finally we discuss how dynamical quark effects may be simulated in a Monte Carlo process with an effective partitioning of low and high eigenmodes. This may be done via selective updating of a trial configuration which highlights the physically relevant effects of light quark modes. (author)

Multiple multicontrol unitary operations: Implementation and applications

Science.gov (United States)

Lin, Qing

2018-04-01

The efficient implementation of computational tasks is critical to quantum computations. In quantum circuits, multicontrol unitary operations are important components. Here, we present an extremely efficient and direct approach to multiple multicontrol unitary operations without decomposition to CNOT and single-photon gates. With the proposed approach, the necessary two-photon operations could be reduced from O( n 3) with the traditional decomposition approach to O( n), which will greatly relax the requirements and make large-scale quantum computation feasible. Moreover, we propose the potential application to the ( n- k)-uniform hypergraph state.

FLIC-overlap fermions and topology

International Nuclear Information System (INIS)

Kamleh, W.; Kusterer, D.J.; Leinweber, D.B.; Williams, A.G.

2003-01-01

APE smearing the links in the irrelevant operators of clover fermions (Fat-Link Irrelevant Clover (FLIC) fermions) provides significant improvement in the condition number of the Hermitian-Dirac operator and gives rise to a factor of two savings in computing the overlap operator. This report investigates the effects of using a highly-improved definition of the lattice field-strength tensor F μν in the fermion action, made possible through the use of APE-smeared fat links in the construction of the irrelevant operators. Spurious double-zero crossings in the spectral flow of the Hermitian-Wilson Dirac operator associated with lattice artifacts at the scale of the lattice spacing are removed with FLIC fermions composed with an O(α 4 )-improved lattice field strength tensor. Hence, FLIC-Overlap fermions provide an additional benefit to the overlap formalism: a correct realization of topology in the fermion sector on the lattice

Non-perturbative renormalisation of {delta}F=2 four-fermion operators in two-flavour QCD

Energy Technology Data Exchange (ETDEWEB)

Dimopoulos, P.; Vladikas, A. [INFN, Sezione di Roma II (Italy)]|[Rome-3 Univ. (Italy). Dipt. di Fisica; Herdoiza, G. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Palombi, F.; Papinutto, M. [CERN, Geneva (Switzerland). Physics Dept., TH Division; Pena, C. [Universidad Autonoma de Madrid (Spain). Dept. de Fisica Teorica C-XI]|[Univ. Autonoma de Madrid (Spain). Inst. de Fisica Teorica UAM/CSIC C-XVI; Wittig, H. [Mainz Univ. (Germany). Inst. fuer Kernphysik

2007-12-15

Using Schroedinger Functional methods, we compute the non-perturbative renormalisation and renormalisation group running of several four-fermion operators, in the framework of lattice simulations with two dynamical Wilson quarks. Two classes of operators have been targeted: (i) those with left-left current structure and four propagating quark fields; (ii) all operators containing two static quarks. In both cases, only the parity-odd contributions have been considered, being the ones that renormalise multiplicatively. Our results, once combined with future simulations of the corresponding lattice hadronic matrix elements, may be used for the computation of phenomenological quantities of interest, such as B{sub K} and B{sub B} (the latter also in the static limit). (orig.)

MSW-resonant fermion mixing during reheating

Science.gov (United States)

Kanai, Tsuneto; Tsujikawa, Shinji

2003-10-01

We study the dynamics of reheating in which an inflaton field couples two flavor fermions through Yukawa-couplings. When two fermions have a mixing term with a constant coupling, we show that the Mikheyev-Smirnov-Wolfenstein (MSW)-type resonance emerges due to a time-dependent background in addition to the standard fermion creation via parametric resonance. This MSW resonance not only alters the number densities of fermions generated by a preheating process but also can lead to the larger energy transfer from the inflaton to fermions. Our mechanism can provide additional source terms for the creation of superheavy fermions which may be relevant for the leptogenesis scenario.

MSW-resonant fermion mixing during reheating

International Nuclear Information System (INIS)

Kanai, Tsuneto; Tsujikawa, Shinji

2003-01-01

We study the dynamics of reheating in which an inflaton field couples two flavor fermions through Yukawa-couplings. When two fermions have a mixing term with a constant coupling, we show that the Mikheyev-Smirnov-Wolfenstein (MSW)-type resonance emerges due to a time-dependent background in addition to the standard fermion creation via parametric resonance. This MSW resonance not only alters the number densities of fermions generated by a preheating process but also can lead to the larger energy transfer from the inflaton to fermions. Our mechanism can provide additional source terms for the creation of superheavy fermions which may be relevant for the leptogenesis scenario

Singular perturbation theory for interacting fermions in two dimensions

International Nuclear Information System (INIS)

Chubukov, A.V.; Maslov, D.L.; Gangadharaiah, S.; Glazman, L.I.

2004-11-01

We consider a system of interacting fermions in two dimensions beyond the second-order perturbation theory in the interaction. It is shown that the mass-shell singularities in the self-energy, arising already at the second order of the perturbation theory, manifest a nonperturbative effect: an interaction with the zero-sound mode. Resuming the perturbation theory for a weak, short-range interaction and accounting for a finite curvature of the fermion spectrum, we eliminate the singularities and obtain the results for the quasi-particle self-energy and the spectral function to all orders in the interaction with the zero-sound mode. A threshold for emission of zero-sound waves leads a non-monotonic variation of the self-energy with energy (or momentum) near the mass shell. Consequently, the spectral function has a kink-like feature. We also study in detail a non-analytic temperature dependence of the specific heat, C(T) ∝T 2 . It turns out that although the interaction with the collective mode results in an enhancement of the fermion self-energy, this interaction does not affect the non-analytic term in C(T) due to a subtle cancellation between the contributions from the real and imaginary parts of the self-energy. For a short-range and weak interaction, this implies that the second-order perturbation theory suffices to determine the non-analytic part of C(T). We also obtain a general form of the non-analytic term in C(T), valid for the case of a generic Fermi liquid, i.e., beyond the perturbation theory. (author)

On charged fermions in two dimensions

International Nuclear Information System (INIS)

Randjbar-Daemi, S.; Salam, A.; Strathdee, J.

1990-09-01

The integer quantum Hall effect and associated magnetic phenomena are reconsidered in a 2-dimensional system with a flat boundary. The electromagnetic properties of this system are governed by an effective Lagrangian which includes an induced Chern-Simons term. The effective lagrangian is relevant for the description of fields which are slowly varying about a uniform magnetic background associated with a fermionic ground state in which a whole number of Landau levels is filled. It is singular for field values that correspond to partially filled levels. The underlying assumption of translation invariance of the fermionic ground state fails in the vicinity of boundaries where the effective field theory is essentially non-local. The width of the boundary layer and the current flowing in it are estimated. (author). 12 refs, 5 figs

Features and stability analysis of non-Schwarzschild black hole in quadratic gravity

International Nuclear Information System (INIS)

Cai, Yi-Fu; Zhang, Hezi; Liu, Junyu; Cheng, Gong; Wang, Min

2016-01-01

Black holes are found to exist in gravitational theories with the presence of quadratic curvature terms and behave differently from the Schwarzschild solution. We present an exhaustive analysis for determining the quasinormal modes of a test scalar field propagating in a new class of black hole backgrounds in the case of pure Einstein-Weyl gravity. Our result shows that the field decay of quasinormal modes in such a non-Schwarzschild black hole behaves similarly to the Schwarzschild one, but the decay slope becomes much smoother due to the appearance of the Weyl tensor square in the background theory. We also analyze the frequencies of the quasinormal modes in order to characterize the properties of new back holes, and thus, if these modes can be the source of gravitational waves, the underlying theories may be testable in future gravitational wave experiments. We briefly comment on the issue of quantum (in)stability in this theory at linear order.

An SU(2) x SU(2) symmetric Higgs-Fermion model with staggered fermions

International Nuclear Information System (INIS)

Berlin, J.; Heller, U.M.

1991-01-01

We have simulated on SU(2)xSU(2) symmetric Higgs-Fermion model with a four component scalar field coupled with a Yukawa type coupling to two flavours of staggered fermions. The results show two qualitatively different behaviours in the broken phase. One for weak coupling where the fermion masses obey the perturbative tree level relation M F =y , and one for strong coupling where the behaviour agrees with a 1/d expansion. (orig.)

Theory of heavy-fermion compounds theory of strongly correlated Fermi-systems

CERN Document Server

Amusia, Miron Ya; Shaginyan, Vasily R; Stephanovich, Vladimir A

2015-01-01

This book explains modern and interesting physics in heavy-fermion (HF) compounds to graduate students and researchers in condensed matter physics. It presents a theory of heavy-fermion (HF) compounds such as HF metals, quantum spin liquids, quasicrystals and two-dimensional Fermi systems. The basic low-temperature properties and the scaling behavior of the compounds are described within the framework of the theory of fermion condensation quantum phase transition (FCQPT). Upon reading the book, the reader finds that HF compounds with quite different microscopic nature exhibit the same non-Fermi liquid behavior, while the data collected on very different HF systems have a universal scaling behavior, and these compounds are unexpectedly uniform despite their diversity. For the reader's convenience, the analysis of compounds is carried out in the context of salient experimental results. The numerous calculations of the non-Fermi liquid behavior, thermodynamic, relaxation and transport properties, being in good...

Feynman rules for fermion-number-violating interactions

International Nuclear Information System (INIS)

Denner, A.; Eck, H.; Hahn, O.; Kueblbeck, J.

1992-01-01

We present simple algorithmic Feynman rules for fermion-number-violating interactions. They do not involve explicit charge-conjugation matrices and resemble closely the familiar rules for Dirac fermions. We insist on a fermion flow through the graphs along fermion lines and get the correct relative signs between different interfering Feynman graphs as in the case of Dirac fermions. We only need the familiar Dirac propagator and fewer vertices than in the usual treatment of fermion-number-violating interactions. (orig.)

SU(8) family unification with boson-fermion balance

CERN Multimedia

CERN. Geneva

2014-01-01

Grand unification has been intensively investigated for over forty years, and many different approaches have been tried. In this talk I propose a model that involves three ingredients that do not appear in the usual constructions: (1) boson--fermion balance without full supersymmetry, (2) canceling the spin 1/2 fermion gauge anomalies against the anomaly from a gauged spin 3/2 gravitino, and (3) using a scalar field representation with non-zero U(1) generator to break the SU(8) gauge symmetry through a ground state which, before dynamical symmetry breaking, has a periodic U(1) generator structure. The model has a number of promising features: (1) natural incorporation of three families, (2) incorporation of the experimentally viable flipped SU(5) model, (3) a symmetry breaking pathway to the standard model using the scalar field required by boson-fermion balance, together with a stage of most attractive channel dynamical symmetry breaking, without postulating additional Higgs fields, (4) vanishing of bare Yuk...

Fermion wavefunctions in magnetized branes: Theta identities and Yukawa couplings

International Nuclear Information System (INIS)

Antoniadis, Ignatios; Kumar, Alok; Panda, Binata

2009-01-01

Computation of Yukawa couplings, determining superpotentials as well as the Kaehler metric, with oblique (non-commuting) fluxes in magnetized brane constructions is an interesting unresolved issue, in view of the importance of such fluxes for obtaining phenomenologically viable models. In order to perform this task, fermion (scalar) wavefunctions on toroidally compactified spaces are presented for general fluxes, parameterized by Hermitian matrices with eigenvalues of arbitrary signatures. We also give explicit mappings among fermion wavefunctions, of different internal chiralities on the tori, which interchange the role of the flux components with the complex structure of the torus. By evaluating the overlap integral of the wavefunctions, we give the expressions for Yukawa couplings among chiral multiplets arising from an arbitrary set of branes (or their orientifold images). The method is based on constructing certain mathematical identities for general Riemann theta functions with matrix valued modular parameter. We briefly discuss an application of the result, for the mass generation of non-chiral fermions, in the SU(5) GUT model presented by us in Antoniadis, Kumar and Panda (2008) .

More on random-lattice fermions

International Nuclear Information System (INIS)

Kieu, T.D.; Institute for Advanced Study, Princeton, NJ; Markham, J.F.; Paranavitane, C.B.

1995-01-01

The lattice fermion determinants, in a given background gauge field, are evaluated for two different kinds of random lattices and compared to those of naive and wilson fermions in the continuum limit. While the fermion doubling is confirmed on one kind of lattices, there is positive evidence that it may be absent for the other, at least for vector interactions in two dimensions. Combined with previous studies, arbitrary randomness by itself is shown to be not a sufficient condition to remove the fermion doublers. 8 refs., 3 figs

High-energy behavior of fermion-meson and meson-meson scattering in a supersymmetric field theory

International Nuclear Information System (INIS)

Opoien, J.W.

1978-01-01

The high-energy behavior of fermion-boson and boson-boson scattering amplitudes of a supersymmetric field theory containing a spin-1/2 fermion field, a scalar field, and a pseudoscalar field is investigated. The results can be easily modified to apply to the Yukawa model and the neutral version of the linear sigma model. The results are also compared to those of fermion-fermion scattering in the same model. In the leading-logarithm approximation, ladders with fermions running along the sides in the t channel and mesons as rungs dominate in each order of two classes of diagrams. The sum of the dominant series give rise to fixed Regge cuts for all amplitudes in each of the three theories. All amplitudes in the supersymmetric theory possess a definite signature factor, while the amplitudes for fermion-fermion and fermion-antifermion scattering in the Y model and the sigma model lack it. The results of the supersymmetric theory are also compared to the results of the spontaneously broken non-Abelian gauge theory

Gapped fermionic spectrum from a domain wall in seven dimension

Science.gov (United States)

Mukhopadhyay, Subir; Rai, Nishal

2018-05-01

We obtain a domain wall solution in maximally gauged seven dimensional supergravity, which interpolates between two AdS spaces and spontaneously breaks a U (1) symmetry. We analyse frequency dependence of conductivity and find power law behaviour at low frequency. We consider certain fermions of supergravity in the background of this domain wall and compute holographic spectral function of the operators in the dual six dimensional theory. We find fermionic operators involving bosons with non-zero expectation value lead to gapped spectrum.

Dual fermion approach to disordered correlated systems

International Nuclear Information System (INIS)

Haase, Patrick

2015-01-01

Disorder is ubiquitous in real materials and influences the physical properties like the conductivity to varying degrees. If electron-electron interactions are strong, theoretical and numerical treatment of these systems becomes challenging. In this thesis a numerical approach is developed to address these systems, treating both interactions and disorder on equal footing. The approach is based on the dual fermion approach for interacting systems developed by Rubtsov et al. Terletska et al. applied the ideas of the dual fermion approach to disordered non-interacting systems. In this approach, the replica trick is used to integrate out the disorder in favor of an effective electron-electron interaction. We extended the approach from Terletska et al. to treat disordered interacting systems. Dual Fermions allow to take into account non-local fluctuations by means of a perturbative expansion around an impurity problem. The impurity reference system is determined self-consistently, analogously to the dynamical mean-field theory. The perturbative expansion is expected to yield good results for small and large values of interaction strength and disorder. A priori, it is not clear what to expect for intermediate values, but experience shows that oftentimes good results are obtained for this region. An advantage of the dual fermion approach is that there is no sign-problem for a single orbital model if quantum Monte Carlo is used to solve the interacting reference system. Additionally, perturbation theory is usually numerically much cheaper than fully solving an interacting lattice or cluster problem. Thus, the dual fermion approach allows to address regions of parameter space that are not accessible to lattice quantum Monte Carlo calculations or cluster extension of dynamical mean-field theory. Cluster extensions of the dynamical mean-field theory are for example the dynamical cluster approximation or the cellular dynamical mean-field theory. The new approach is benchmarked

The algebras of higher order currents of the fermionic Gross-Neveu model

International Nuclear Information System (INIS)

Saltini, Luis Eduardo

1996-01-01

Results are reported from our studies on the following 2-dimensional field theories: the supersymmetric non-linear sigma model and the fermionic Gross-Neveu model. About the supersymmetric non-linear sigma model, an attempt is made to solve the the algebraic problem of finding the non-local conserved charges and the corresponding algebra, extending the methods described in a previous article for the case of the purely bosonic non linear sigma model. For the fermionic Gross-Neveu model, we intend to construct the conserved currents and the respective charges, related to the abelian U(1) symmetry and non-abelian SU(n) symmetry, at the conformal point and calculate the correlation functions between them. From these results at the conformal point, we want to study the effects of perturbation to get a massive but integral theory

Perfect state transfer in unitary Cayley graphs over local rings

Directory of Open Access Journals (Sweden)

Yotsanan Meemark

2014-12-01

Full Text Available In this work, using eigenvalues and eigenvectors of unitary Cayley graphs over finite local rings and elementary linear algebra, we characterize which local rings allowing PST occurring in its unitary Cayley graph. Moreover, we have some developments when $R$ is a product of local rings.

Robust Learning Control Design for Quantum Unitary Transformations.

Science.gov (United States)

Wu, Chengzhi; Qi, Bo; Chen, Chunlin; Dong, Daoyi

2017-12-01

Robust control design for quantum unitary transformations has been recognized as a fundamental and challenging task in the development of quantum information processing due to unavoidable decoherence or operational errors in the experimental implementation of quantum operations. In this paper, we extend the systematic methodology of sampling-based learning control (SLC) approach with a gradient flow algorithm for the design of robust quantum unitary transformations. The SLC approach first uses a "training" process to find an optimal control strategy robust against certain ranges of uncertainties. Then a number of randomly selected samples are tested and the performance is evaluated according to their average fidelity. The approach is applied to three typical examples of robust quantum transformation problems including robust quantum transformations in a three-level quantum system, in a superconducting quantum circuit, and in a spin chain system. Numerical results demonstrate the effectiveness of the SLC approach and show its potential applications in various implementation of quantum unitary transformations.

Ultracold fermion race is on

International Nuclear Information System (INIS)

Hulet, R.

1999-01-01

At the quantum level, particles behave very differently depending on whether their spin angular momentum is an integer or a half-integer. Half-integer spin particles are known as fermions, and include all the constituents of atoms: electrons, protons and neutrons. Bosons, on the other hand, are particles with integer spin, such as photons. Atoms are fermions if they are composed of an odd number of particles, like helium-3 or lithium-6. If they have an even number of constituents, like hydrogen, helium-4 or lithium-7, they are known as bosons. Fermions and bosons behave in profoundly different ways under certain conditions, especially at low temperatures. Four years ago, physicists created a Bose condensate, a quantum degenerate gas of bosons. Now the race is on to do the same with fermions. Deborah Jin's group at the US National Institute of Standards and Technology (NIST) and the University of Colorado has cooled a fermion gas to the lowest temperature yet (B DeMarco 1999 Phys. Rev. Lett. 82 4208). And John Thomas and co-workers at Duke University have set a new record for the length of time that fermions can be trapped using lasers (K O'Hara 1999 Phys. Rev. Lett. 82 4204). In this article the author describes the latest advances in the race to create a quantum degenerate gas of fermions. (UK)

Negative-Parity Baryon Masses Using O(a)-improved Fermion Action

Energy Technology Data Exchange (ETDEWEB)

M. Gockeler; R. Horsley; D. Pleiter; P.E.L. Rakow; G. Schierholz; C.M. Maynard; D.G. Richards

2001-06-01

We present a calculation of the mass of the lowest-lying negative-parity J=1/2{sup {minus}} state in quenched QCD. Results are obtained using a non-perturbatively {Omicron}(a)-improved clover fermion action, and a splitting found between the masses of the nucleon, and its parity partner. The calculation is performed on two lattice volumes, and at three lattice spacings, enabling a study of both finite-volume and finite lattice-spacing uncertainties. A comparison is made with results obtained using the unimproved Wilson fermion action.

The Bethe-Salpeter equation with fermions

International Nuclear Information System (INIS)

Efimov, G.V.

2007-01-01

The Bethe-Salpeter (BS) equation in the ladder approximation is studied within a fermion theory: two fermion fields (constituents) with mass m interacting via an exchange of a scalar field with mass μ. The BS equation can be written in the form of an integral equation in the configuration Euclidean x-space with the symmetric kernel K for which Tr K 2 = ∞ due to the singular character of the fermion propagator. This kernel is represented in the form K = K 0 + K I . The operator K 0 with Tr K 0 2 ∞ is of the 'fall at the center' potential type and describes a continuous spectrum only. Besides the presence of this operator leads to a restriction on the value of the coupling constant. The kernel K I with Tr K I 2 2 c 2 and the variational procedure of calculations of eigenvalues and eigenfunctions can be applied. The quantum pseudoscalar and scalar mesodynamics is considered. The binding energy of the state 1 + (deuteron) as a function of the coupling constant is calculated in the framework of the procedure formulated above. It is shown that this bound state is absent in the pseudoscalar mesodynamics and does exist in the scalar mesodynamics. A comparison with the non-relativistic Schroedinger picture is made. (author)

Signatures of non-Abelian anyons in the thermodynamics of an interacting fermion model

Science.gov (United States)

Borcherding, Daniel; Frahm, Holger

2018-05-01

The contribution of anyonic degrees of freedom emerging in the non-Abelian spin sector of a one-dimensional system of interacting fermions carrying both spin and SU(N f ) orbital degrees of freedom to the thermodynamic properties of the latter is studied based on the exact solution of the model. For sufficiently small temperatures and magnetic fields the anyons appear as zero energy modes localized at the massive kink excitations (Tsvelik 2014 Phys. Rev. Lett. 113 066401). From their quantum dimension they are identified as spin- anyons. The density of kinks (and anyons) can be controlled by an external magnetic field leading to the formation of a collective state of these anyons described by a parafermion conformal field theory for large fields. Based on the numerical analysis of the thermodynamic Bethe ansatz equations we propose a phase diagram for the anyonic modes.

Fermion masses and multiplicity

International Nuclear Information System (INIS)

Ramond, P.

1986-01-01

A general survey and analysis of fermion masses is presented in terms of both the known low energy gauge structure and of the simplest GUT structure. The replication of fermion families is discussed in the context of possible family group structures. Sample family gauge groups are presented in the cases of three and four chiral families, using ABJ and Witten anomalies to restrict the maximal gauged family group. The possible relevance of the family group to the fermion mass hierarchy is discussed in the context of various models. (author)

Mirror fermions and cosmology

International Nuclear Information System (INIS)

Senjanovic, G.; Virginia Polytechnic Inst. and State Univ., Blacksburg

1984-07-01

Extended supersymmetry, Kaluza-Klein theory and family unification all suggest the existence of mirror fermions, with same quantum numbers but opposite helicities from ordinary fermions. The laboratory and especially cosmological implications of such particles are reviewed and summarized. (author)

Fermion bag solutions to some unsolved sign problems

Science.gov (United States)

Li, Anyi; Chandrasekharan, Shailesh

2012-03-01

Some interesting lattice four-fermion models containing N flavors of staggered fermions with Z2 and U(1) chiral symmetries suffer from sign problems in the auxiliary field approach. Earlier calculations have either ignored these sign problems or have circumvented them by adding conjugate fermion fields which changes the model. In this talk we show that the recently proposed fermion bag approach solves these sign problems. The basic idea of the new approach is to collect unpaired fermionic degrees of freedom inside a fermion bag. A resummation of all fermion world lines inside the bag is then sufficient to solve the sign problems. The fermion bag approach provides new opportunities to solve in these ``unsolved'' four-fermion models in the chiral limit efficiently.

Simulation of QCD with N_f=2+1 flavors of non-perturbatively improved Wilson fermions

International Nuclear Information System (INIS)

Bruno, Mattia; Djukanovic, Dalibor; Engel, Georg P.; Francis, Anthony; Herdoiza, Gregorio; Horch, Hanno; Korcyl, Piotr; Korzec, Tomasz; Papinutto, Mauro; Schaefer, Stefan; Scholz, Enno E.; Simeth, Jakob; Simma, Hubert; Söldner, Wolfgang

2015-01-01

We describe a new set of gauge configurations generated within the CLS effort. These ensembles have N_f=2+1 flavors of non-perturbatively improved Wilson fermions in the sea with the Lüscher-Weisz action used for the gluons. Open boundary conditions in time are used to address the problem of topological freezing at small lattice spacings and twisted-mass reweighting for improved stability of the simulations. We give the bare parameters at which the ensembles have been generated and how these parameters have been chosen. Details of the algorithmic setup and its performance are presented as well as measurements of the pion and kaon masses alongside the scale parameter t_0.

Excited fermions

International Nuclear Information System (INIS)

Boudjema, F.; Djouadi, A.; Kneur, J.L.

1992-01-01

The production of excited fermions with mass above 100 GeV is considered. f→Vf (1) decay widths are calculated where V=γ, Z or W. Excited fermion pair production in e + e - annihilation and in γγ collisions, and single production in e + e - annihilation, eγ and γγ collisions is also discussed. Cross sections are calculated for all these cases. The discovery potential of the NLC at 500 GeV is compared with that of other colliders. (K.A.) 15 refs., 5 figs., 2 tabs

Consciousness, intentionality, and community: Unitary perspectives and research.

Science.gov (United States)

Zahourek, Rothlyn P; Larkin, Dorothy M

2009-01-01

Consciousness and intentionality often have been related and studied together. These concepts also are readily viewed and understood for practice, research, and education in a unitary paradigm. How these ideas relate to community is less known. Considering the expansion of our capacity for communication through the World Wide Web and other technologic advances and appreciating recent research on the nonlocal character of intentionality and consciousness, it is more apparent how concepts of community can be seen in the same unitary context. The authors address these issues and review relevant nursing research.

Electric dipole moments of charged leptons with sterile fermions

International Nuclear Information System (INIS)

Abada, Asmaa; Toma, Takashi

2016-01-01

We address the impact of sterile fermions on charged lepton electric dipole moments. Any experimental signal of these observables calls for scenarios of physics beyond the Standard Model providing new sources of CP violation. In this work, we consider a minimal extension of the Standard Model via the addition of sterile fermions which mix with active neutrinos and we derive the corresponding analytical expressions for the electric dipole moments of charged leptons at two-loop order. Our study reveals that, in order to have a non-vanishing contribution in this framework, the minimal extension necessitates the addition of at least 2 sterile fermion states to the Standard Model field content. Our conclusion is that sterile neutrinos can give significant contributions to the charged lepton electric dipole moments, some of them lying within present and future experimental sensitivity if the masses of the non-degenerate sterile states are both above the electroweak scale. The Majorana nature of neutrinos is also important in order to allow for significative contributions to the charged lepton electric dipole moments. In our analysis we impose all available experimental and observational constraints on sterile neutrinos and we further discuss the prospect of probing this scenario at low and high energy experiments.

Electric dipole moments of charged leptons with sterile fermions

Energy Technology Data Exchange (ETDEWEB)

Abada, Asmaa; Toma, Takashi [Laboratoire de Physique Théorique, CNRS, University Paris-Sud, Université Paris-Saclay, 91405 Orsay (France)

2016-02-26

We address the impact of sterile fermions on charged lepton electric dipole moments. Any experimental signal of these observables calls for scenarios of physics beyond the Standard Model providing new sources of CP violation. In this work, we consider a minimal extension of the Standard Model via the addition of sterile fermions which mix with active neutrinos and we derive the corresponding analytical expressions for the electric dipole moments of charged leptons at two-loop order. Our study reveals that, in order to have a non-vanishing contribution in this framework, the minimal extension necessitates the addition of at least 2 sterile fermion states to the Standard Model field content. Our conclusion is that sterile neutrinos can give significant contributions to the charged lepton electric dipole moments, some of them lying within present and future experimental sensitivity if the masses of the non-degenerate sterile states are both above the electroweak scale. The Majorana nature of neutrinos is also important in order to allow for significative contributions to the charged lepton electric dipole moments. In our analysis we impose all available experimental and observational constraints on sterile neutrinos and we further discuss the prospect of probing this scenario at low and high energy experiments.

New fermion mass textures from anomalous U(1) symmetries with baryon and lepton number conservation

CERN Document Server

Leontaris, George K

2000-01-01

In this paper, we present solutions to the fermion mass hierarchy problem in the context of the minimal supersymmetric standard theory augmented by an anomalous family-dependent U(1)_X symmetry. The latter is spontaneously broken by non-zero vevs of a pair of singlet fields whose magnitude is determined through the D- and F-flatness conditions of the superpotential. We derive the general solutions to the anomaly cancellation conditions and show that they allow numerous choices for the U(1)_X fermion charges which give several fermion mass textures in agreement with the observed fermion mass hierarchy and mixing. Solutions with U(1)_X fermion charge assignments are found which forbid or substantially suppress the dangerous baryon and lepton number violating operators and the lepton-higgs mixing coupling while a higgs mixing mass classification of the fermion mass textures with respect to the sum of the doublet-higgs U(1)_X-charges and show that suppression of dimension-five operators naturally occurs for vario...

How real are composite fermions?

International Nuclear Information System (INIS)

Kang, W.; Stormer, H.L.; Pfeiffer, L.N.; Baldwin, K.W.; West, K.W.

1995-01-01

A new picture of fractional quantum Hall effect (FQHE) in terms of a novel particle called composite fermion has emerged recently. A composite fermion is a composite of two flux quanta which are effectively bound to an electron as a result of electron-electron interaction. A system of electrons at half-filled Landau level can be transformed to an equivalent system of composite fermions at zero effective magnetic field with a distinct Fermi surface. The FQHE is then viewed as the integral quantum Hall effect of composite fermions away from half-filling. In order to test for these new particles, we have studied transport of anti-dot superlattices in a two-dimensional electron gas. At low magnetic fields electron transport exhibits well-known resonances at fields where the classical cyclotron orbit becomes commensurate with the anti-dot lattice. At half-filling we observe the same dimensional resonances. This establishes the ''semi-classical'' behavior of composite fermions. (orig.)

Theoretical studies of strongly correlated fermions

Energy Technology Data Exchange (ETDEWEB)

Logan, D [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

1997-04-01

Strongly correlated fermions are investigated. An understanding of strongly correlated fermions underpins a diverse range of phenomena such as metal-insulator transitions, high-temperature superconductivity, magnetic impurity problems and the properties of heavy-fermion systems, in all of which local moments play an important role. (author).

Relativistic time-dependent Fermion-mass renormalization using statistical regularization

Science.gov (United States)

Kutnink, Timothy; McMurray, Christian; Santrach, Amelia; Hockett, Sarah; Barcus, Scott; Petridis, Athanasios

2017-09-01

The time-dependent electromagnetically self-coupled Dirac equation is solved numerically by means of the staggered-leap-frog algorithm with reflecting boundary conditions. The stability region of the method versus the interaction strength and the spatial-grid size over time-step ratio is established. The expectation values of several dynamic operators are then evaluated as functions of time. These include the fermion and electromagnetic energies and the fermion dynamic mass. There is a characteristic, non-exponential, oscillatory dependence leading to asymptotic constants of these expectation values. In the case of the fermion mass this amounts to renormalization. The dependence of the expectation values on the spatial-grid size is evaluated in detail. Furthermore, the contribution of positive and negative energy states to the asymptotic values and the gauge fields is analyzed. Statistical regularization, employing a canonical ensemble whose temperature is the inverse of the grid size, is used to remove the grid-size and momentum-dependence and produce a finite result in the continuum limit.

Fermion-induced quantum critical points.

Science.gov (United States)

Li, Zi-Xiang; Jiang, Yi-Fan; Jian, Shao-Kai; Yao, Hong

2017-08-22

A unified theory of quantum critical points beyond the conventional Landau-Ginzburg-Wilson paradigm remains unknown. According to Landau cubic criterion, phase transitions should be first-order when cubic terms of order parameters are allowed by symmetry in the Landau-Ginzburg free energy. Here, from renormalization group analysis, we show that second-order quantum phase transitions can occur at such putatively first-order transitions in interacting two-dimensional Dirac semimetals. As such type of Landau-forbidden quantum critical points are induced by gapless fermions, we call them fermion-induced quantum critical points. We further introduce a microscopic model of SU(N) fermions on the honeycomb lattice featuring a transition between Dirac semimetals and Kekule valence bond solids. Remarkably, our large-scale sign-problem-free Majorana quantum Monte Carlo simulations show convincing evidences of a fermion-induced quantum critical points for N = 2, 3, 4, 5 and 6, consistent with the renormalization group analysis. We finally discuss possible experimental realizations of the fermion-induced quantum critical points in graphene and graphene-like materials.Quantum phase transitions are governed by Landau-Ginzburg theory and the exceptions are rare. Here, Li et al. propose a type of Landau-forbidden quantum critical points induced by gapless fermions in two-dimensional Dirac semimetals.

Renormalization of the Abelian–Higgs model in the Rξ and Unitary gauges and the physicality of its scalar potential

Directory of Open Access Journals (Sweden)

Nikos Irges

2017-11-01

Full Text Available We perform an old school, one-loop renormalization of the Abelian–Higgs model in the Unitary and Rξ gauges, focused on the scalar potential and the gauge boson mass. Our goal is to demonstrate in this simple context the validity of the Unitary gauge at the quantum level, which could open the way for an until now (mostly avoided framework for loop computations. We indeed find that the Unitary gauge is consistent and equivalent to the Rξ gauge at the level of β-functions. Then we compare the renormalized, finite, one-loop Higgs potential in the two gauges and we again find equivalence. This equivalence needs not only a complete cancellation of the gauge fixing parameter ξ from the Rξ gauge potential but also requires its ξ-independent part to be equal to the Unitary gauge result. We follow the quantum behavior of the system by plotting Renormalization Group trajectories and Lines of Constant Physics, with the former the well known curves and with the latter, determined by the finite parts of the counter-terms, particularly well suited for a comparison with non-perturbative studies.

Studies of heavy fermion systems: Progress report, July 1, 1986-December 31, 1987

International Nuclear Information System (INIS)

Stewart, G.R.

1987-08-01

Studies of the resistivity, susceptibility, and specific heat of the new heavy fermion system UPt/sub 5-x/Au/sub x/ have shown: (1) the high effective mass, m*, can be varied by almost an order of magnitude by varying x near x = 1; and (2) the occurrence of high m* in this system and (presumably) in heavy fermion systems in general is typified by a nearness to magnetic instability. High field (24 T) specific heat studies of CeCu 6 show a total suppression of the low temperature heavy fermion ground state by magnetic field, in direct contradiction of present non-interacting ''Kondo lattice'' theory

Fluctuations and instabilities of a holographic metal

Science.gov (United States)

Jokela, Niko; Järvinen, Matti; Lippert, Matthew

2013-02-01

We analyze the quasinormal modes of the D2-D8' model of 2+1-dimensional, strongly-coupled, charged fermions in a background magnetic field and at non-zero density. The model is known to include a quantum Hall phase with integer filling fraction. As expected, we find a hydrodynamical diffusion mode at small momentum and the nonzero-temperature holographic zero sound, which becomes massive above a critical magnetic field. We confirm the previously-known thermodynamic instability. In addition, we discover an instability at low temperature, large mass, and in a charge density and magnetic field range near the quantum Hall phase to an inhomogeneous striped phase.

Bootstrapping 3D fermions

Energy Technology Data Exchange (ETDEWEB)

Iliesiu, Luca [Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 (United States); Kos, Filip; Poland, David [Department of Physics, Yale University, New Haven, CT 06520 (United States); Pufu, Silviu S. [Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 (United States); Simmons-Duffin, David [School of Natural Sciences, Institute for Advanced Study, Princeton, NJ 08540 (United States); Yacoby, Ran [Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 (United States)

2016-03-17

We study the conformal bootstrap for a 4-point function of fermions 〈ψψψψ〉 in 3D. We first introduce an embedding formalism for 3D spinors and compute the conformal blocks appearing in fermion 4-point functions. Using these results, we find general bounds on the dimensions of operators appearing in the ψ×ψ OPE, and also on the central charge C{sub T}. We observe features in our bounds that coincide with scaling dimensions in the Gross-Neveu models at large N. We also speculate that other features could coincide with a fermionic CFT containing no relevant scalar operators.

Dynamical fermions in lattice quantum chromodynamics

Energy Technology Data Exchange (ETDEWEB)

Szabo, Kalman

2007-07-01

The thesis presentS results in Quantum Chromo Dynamics (QCD) with dynamical lattice fermions. The topological susceptibilty in QCD is determined, the calculations are carried out with dynamical overlap fermions. The most important properties of the quark-gluon plasma phase of QCD are studied, for which dynamical staggered fermions are used. (orig.)

Dynamical fermions in lattice quantum chromodynamics

International Nuclear Information System (INIS)

Szabo, Kalman

2007-01-01

The thesis presentS results in Quantum Chromo Dynamics (QCD) with dynamical lattice fermions. The topological susceptibilty in QCD is determined, the calculations are carried out with dynamical overlap fermions. The most important properties of the quark-gluon plasma phase of QCD are studied, for which dynamical staggered fermions are used. (orig.)

Fermion condensation and gapped domain walls in topological orders

Energy Technology Data Exchange (ETDEWEB)

Wan, Yidun [Department of Physics and Center for Field Theory and Particle Physics, Fudan University,Shanghai 200433 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University,Nanjing 210093 (China); Perimeter Institute for Theoretical Physics,Waterloo N2L 2Y5, Ontario (Canada); Wang, Chenjie [Perimeter Institute for Theoretical Physics,Waterloo N2L 2Y5, Ontario (Canada)

2017-03-31

We study fermion condensation in bosonic topological orders in two spatial dimensions. Fermion condensation may be realized as gapped domain walls between bosonic and fermionic topological orders, which may be thought of as real-space phase transitions from bosonic to fermionic topological orders. This picture generalizes the previous idea of understanding boson condensation as gapped domain walls between bosonic topological orders. While simple-current fermion condensation was considered before, we systematically study general fermion condensation and show that it obeys a Hierarchy Principle: a general fermion condensation can always be decomposed into a boson condensation followed by a minimal fermion condensation. The latter involves only a single self-fermion that is its own anti-particle and that has unit quantum dimension. We develop the rules of minimal fermion condensation, which together with the known rules of boson condensation, provides a full set of rules for general fermion condensation.

Negative-parity baryon masses using an Ο(α)-improved fermion action

International Nuclear Information System (INIS)

Goeckeler, M.; Rakow, P.E.L.; Maynard, C.M.; Richards, D.G.; Old Dominion Univ., Norfolk, VA

2001-06-01

We present a calculation of the mass of the lowest-lying negative-parity J = 1/2 - state in quenched QCD. Results are obtained using a non-perturbatively O(a)-improved clover fermion action, and a splitting is found between the masses of the nucleon, and its parity partner. The calculation is performed on two lattice volumes and at three lattice spacings, enabling a study of both finite-volume and finite lattice-spacing uncertainties. A comparison is made with results obtained using the unimproved Wilson fermion action. (orig.)

Fermionic Markov Chains

OpenAIRE

Fannes, Mark; Wouters, Jeroen

2012-01-01

We study a quantum process that can be considered as a quantum analogue for the classical Markov process. We specifically construct a version of these processes for free Fermions. For such free Fermionic processes we calculate the entropy density. This can be done either directly using Szeg\\"o's theorem for asymptotic densities of functions of Toeplitz matrices, or through an extension of said theorem to rates of functions, which we present in this article.

Space-time supersymmetry of extended fermionic strings in 2 + 2 dimensions

International Nuclear Information System (INIS)

Ketov, S.V.

1993-04-01

The N = 2 fermionic string theory is revisited in light of its recently proposed equivalence to the non-compact N = 4 fermionic string model. The issues of space-time Lorentz covariance and supersymmetry for the BRST quantized N = 2 strings living in uncompactified 2 + 2 dimensions are discussed. The equivalent local quantum supersymmetric field theory appears to be the most transparent way to represent the space-time symmetries of the extended fermionic strings and their interactions. Our considerations support the Siegel's ideas about the presence of SO(2,2) Lorentz symmetry as well as at least two self-dual space-time supersymmetries in the theory of the N = 2(4) fermionic strings, though we do not have a compelling reason to argue about the necessity of the maximal space-time supersymmetry. The world-sheet arguments about the absence of all string massive modes in the physical spectrum, and the vanishing of all string-loop amplitudes in the Polyakov approach, are given on the basis of general consistency of the theory. (orig.)

Interpretation of Fermion system equilibration by energy fluid motion

International Nuclear Information System (INIS)

Jang, S.

1990-01-01

We study the equilibration of fermion system with the help of both linear and non-linear master equations which are originated from the extended time-dependent Hartree-Fock equation of motion. We show how the non-linear master equation for nucleon occupation number transforms into the Navier-Stokes type of one dimensional equation for non-stationary flow of a compressible and viscous fluid. Physical consequences of these equations are investigated by providing illustrative examples

Optical Lattice Gases of Interacting Fermions

Science.gov (United States)

2015-12-02

interacting Fermi gases has topological properties similar to the conventional chiral p- wave state. These include a non-zero Chern number and the...interacting cold gases with broad impacts on the interfaces with condensed matter and particle physics . Applications and experiments of some of the physics ...AFRL-AFOSR-VA-TR-2016-0016 Optical Lattice Gases of Interacting Fermions Wensheng Vincent Liu UNIVERSITY OF PITTSBURGH Final Report 12/02/2015

Gravitational Quasinormal Modes of Regular Phantom Black Hole

Directory of Open Access Journals (Sweden)

Jin Li

2017-01-01

Full Text Available We investigate the gravitational quasinormal modes (QNMs for a type of regular black hole (BH known as phantom BH, which is a static self-gravitating solution of a minimally coupled phantom scalar field with a potential. The studies are carried out for three different spacetimes: asymptotically flat, de Sitter (dS, and anti-de Sitter (AdS. In order to consider the standard odd parity and even parity of gravitational perturbations, the corresponding master equations are derived. The QNMs are discussed by evaluating the temporal evolution of the perturbation field which, in turn, provides direct information on the stability of BH spacetime. It is found that in asymptotically flat, dS, and AdS spacetimes the gravitational perturbations have similar characteristics for both odd and even parities. The decay rate of perturbation is strongly dependent on the scale parameter b, which measures the coupling strength between phantom scalar field and the gravity. Furthermore, through the analysis of Hawking radiation, it is shown that the thermodynamics of such regular phantom BH is also influenced by b. The obtained results might shed some light on the quantum interpretation of QNM perturbation.

Minimal unitary realizations of exceptional U-duality groups and their subgroups as quasiconformal groups

International Nuclear Information System (INIS)

Gunaydin, Murat; Pavlyk, Oleksandr

2005-01-01

We study the minimal unitary representations of noncompact exceptional groups that arise as U-duality groups in extended supergravity theories. First we give the unitary realizations of the exceptional group E 8(-24) in SU*(8) as well as SU(6,2) covariant bases. E 8(-24) has E 7 x SU(2) as its maximal compact subgroup and is the U-duality group of the exceptional supergravity theory in d=3. For the corresponding U-duality group E 8(8) of the maximal supergravity theory the minimal realization was given. The minimal unitary realizations of all the lower rank noncompact exceptional groups can be obtained by truncation of those of E 8(-24) and E 8(8) . By further truncation one can obtain the minimal unitary realizations of all the groups of the 'Magic Triangle'. We give explicitly the minimal unitary realizations of the exceptional subgroups of E 8(-24) as well as other physically interesting subgroups. These minimal unitary realizations correspond, in general, to the quantization of their geometric actions as quasi-conformal groups. (author)

Piaget's Egocentrism: A Unitary Construct?

Science.gov (United States)

Ruthven, Avis J.; Cunningham, William L.

In order to determine whether egocentrism can be conceptualized as a unitary construct, 100 children (51 four-year-olds, 37 five-year-olds, and 12 six-year-olds) were administered a visual/spatial perspective task, a cognitive/communicative task, and an affective task. All tasks were designed to measure different facets of egocentrism. The 50…

Generalized unitaries and the Picard group

Indian Academy of Sciences (India)

some explicit calculations of that type.) So the range of this .... when we restrict our attention to generalized unitaries and full modules, that is, to modules. E for which BE = B. For every ..... without dividing out equivalence classes. But there is no ...

Quark-lepton universality and large leptonic mixing

International Nuclear Information System (INIS)

Joshipura, Anjan S.; Smirnov, A.Yu.

2006-01-01

A unified description of fermionic mixing is proposed which assumes that in certain basis (i) a single complex unitary matrix V diagonalizes mass matrices of all fermions to the leading order (ii) the SU(5) relation M d =M l T exists between the mass matrices of the down quarks and the charged leptons, and (iii) M d - bar =M d . These assumptions automatically lead to different mixing patterns for quarks and leptons: Quarks remain unmixed to leading order (i.e. V CKM =1) while leptons have non-trivial mixing given by a symmetric unitary matrix V PMNS 0 =V T V. V depends on two physical mixing angles and for values of these angles ∼20 o -25 o it reproduces the observed mixing patterns rather well. We identify conditions under which the universal mixing V follows from the universal mass matrices of fermions. Relatively small perturbations to the leading order structure lead to the CKM mixing and corrections to V PMNS 0 . We find that if the correction matrix equals the CKM matrix, the resulting lepton mixing agrees well with data and predicts (V PMNS ) e3 >0.08

Symmetric mixed states of n qubits: Local unitary stabilizers and entanglement classes

Energy Technology Data Exchange (ETDEWEB)

Lyons, David W.; Walck, Scott N. [Lebanon Valley College, Annville, Pennsylvania 17003 (United States)

2011-10-15

We classify, up to local unitary equivalence, local unitary stabilizer Lie algebras for symmetric mixed states of n qubits into six classes. These include the stabilizer types of the Werner states, the Greenberger-Horne-Zeilinger state and its generalizations, and Dicke states. For all but the zero algebra, we classify entanglement types (local unitary equivalence classes) of symmetric mixed states that have those stabilizers. We make use of the identification of symmetric density matrices with polynomials in three variables with real coefficients and apply the representation theory of SO(3) on this space of polynomials.

Fermions and bosons : a 'spinless' approach

International Nuclear Information System (INIS)

Oliveira, P.M.C. de; Ribeiro, S.C.

1980-07-01

The fundamental difference between fermions and bosons is presented. The treatment used is based only on indistinguishability and its related implications on interference, with no mention to spin. Comparison between indistinguishable (fermions or bosons) and distinguishable identical particles are also made, yielding the enhancement (bosons) or inhibition (fermions) factors which determine the quantum distribution equations. (Author) [pt

Chiral unitary theory: Application to nuclear problems

Indian Academy of Sciences (India)

Chiral unitary theory: Application to nuclear problems ... Physics Department, Nara Women University, Nara, Japan. 5 ... RCNP, Osaka University, Osaka, Japan ...... We acknowledge partial financial support from the DGICYT under contract ...

Fermion masses from dimensional reduction

International Nuclear Information System (INIS)

Kapetanakis, D.; Zoupanos, G.

1990-01-01

We consider the fermion masses in gauge theories obtained from ten dimensions through dimensional reduction on coset spaces. We calculate the general fermion mass matrix and we apply the mass formula in illustrative examples. (orig.)

Fermion masses from dimensional reduction

Energy Technology Data Exchange (ETDEWEB)

Kapetanakis, D. (National Research Centre for the Physical Sciences Democritos, Athens (Greece)); Zoupanos, G. (European Organization for Nuclear Research, Geneva (Switzerland))

1990-10-11

We consider the fermion masses in gauge theories obtained from ten dimensions through dimensional reduction on coset spaces. We calculate the general fermion mass matrix and we apply the mass formula in illustrative examples. (orig.).

A mapping from the unitary to doubly stochastic matrices and symbols on a finite set

Science.gov (United States)

Karabegov, Alexander V.

2008-11-01

We prove that the mapping from the unitary to doubly stochastic matrices that maps a unitary matrix (ukl) to the doubly stochastic matrix (|ukl|2) is a submersion at a generic unitary matrix. The proof uses the framework of operator symbols on a finite set.

Phantom cosmologies and fermions

International Nuclear Information System (INIS)

Chimento, Luis P; Forte, Monica; Devecchi, Fernando P; Kremer, Gilberto M

2008-01-01

Form invariance transformations can be used for constructing phantom cosmologies starting with conventional cosmological models. In this work we reconsider the scalar field case and extend the discussion to fermionic fields, where the 'phantomization' process exhibits a new class of possible accelerated regimes. As an application we analyze the cosmological constant group for a fermionic seed fluid

Null-plane quantization of fermions

International Nuclear Information System (INIS)

Mustaki, D.

1990-01-01

Massive Dirac fermions are canonically quantized on the null plane using the Dirac-Bergmann algorithm. The procedure is carried out in the framework of quantum electrodynamics as an illustration of a rigorous treatment of interacting fermion fields

Improved lattice fermion action for heavy quarks

International Nuclear Information System (INIS)

Cho, Yong-Gwi; Hashimoto, Shoji; Jüttner, Andreas; Kaneko, Takashi; Marinkovic, Marina; Noaki, Jun-Ichi; Tsang, Justus Tobias

2015-01-01

We develop an improved lattice action for heavy quarks based on Brillouin-type fermions, that have excellent energy-momentum dispersion relation. The leading discretization errors of O(a) and O(a"2) are eliminated at tree-level. We carry out a scaling study of this improved Brillouin fermion action on quenched lattices by calculating the charmonium energy-momentum dispersion relation and hyperfine splitting. We present a comparison to standard Wilson fermions and domain-wall fermions.

Fermions on the electroweak string

CERN Document Server

Moreno, J M; Quirós, Mariano; Moreno, J M; Oaknin, D H; Quiros, M

1995-01-01

We construct a simple class of exact solutions of the electroweak theory including the naked Z--string and fermion fields. It consists in the Z--string configuration (\\phi,Z_\\theta), the {\\it time} and z components of the neutral gauge bosons (Z_{0,3},A_{0,3}) and a fermion condensate (lepton or quark) zero mode. The Z--string is not altered (no feed back from the rest of fields on the Z--string) while fermion condensates are zero modes of the Dirac equation in the presence of the Z--string background (no feed back from the {\\it time} and z components of the neutral gauge bosons on the fermion fields). For the case of the n--vortex Z--string the number of zero modes found for charged leptons and quarks is (according to previous results by Jackiw and Rossi) equal to |n|, while for (massless) neutrinos is |n|-1. The presence of fermion fields in its core make the obtained configuration a superconducting string, but their presence (as well as that of Z_{0,3},A_{0,3}) does not enhance the stability of the Z--stri...

Probabilistic Q-function distributions in fermionic phase-space

International Nuclear Information System (INIS)

Rosales-Zárate, Laura E C; Drummond, P D

2015-01-01

We obtain a positive probability distribution or Q-function for an arbitrary fermionic many-body system. This is different to previous Q-function proposals, which were either restricted to a subspace of the overall Hilbert space, or used Grassmann methods that do not give probabilities. The fermionic Q-function obtained here is constructed using normally ordered Gaussian operators, which include both non-interacting thermal density matrices and BCS states. We prove that the Q-function exists for any density matrix, is real and positive, and has moments that correspond to Fermi operator moments. It is defined on a finite symmetric phase-space equivalent to the space of real, antisymmetric matrices. This has the natural SO(2M) symmetry expected for Majorana fermion operators. We show that there is a physical interpretation of the Q-function: it is the relative probability for observing a given Gaussian density matrix. The distribution has a uniform probability across the space at infinite temperature, while for pure states it has a maximum value on the phase-space boundary. The advantage of probabilistic representations is that they can be used for computational sampling without a sign problem. (fast track communication)

Construction of closed fermionic string models in four dimensions

International Nuclear Information System (INIS)

Lewellen, D.C.

1987-01-01

It is possible to construct consistent closed string models directly in four space-time dimensions if reparametrization invariance, conformal invariance and world sheet supersymmetry are properly accounted for. In the context of string models whose internal degrees of freedom are represented by free world sheet fermions, it is possible to completely solve for the above requirements, providing a simple set of rules for constructing string models. N = 1 supersymmetric and non-supersymmetric heterotic type string models with chiral fermions and realistic gauge groups, as well as generalized type II models with realistic gauge groups, can easily be constructed. Many other string models can be constructed using similar methods based on free world sheet bosons

Low energy fermion number violation

International Nuclear Information System (INIS)

Peccei, R.D.

1989-01-01

After a brief aside on charge quantization in the standard electroweak theory, I concentrate on various aspects of anomaly induced fermion number violation in the standard model. A critical analysis of the role of sphalerons for the universe's baryon asymmetry is presented and the importance of calculating directly fermion number violating Green's functions is stressed. A physical interpretation of the recent observation of Ringwald, that coherent effects in the electroweak theory lead to catastrophic fermion number violation at 100 TeV, is discussed. Possible quantum effects which might spoil this semi-classical picture are examined

Interacting composite fermions

DEFF Research Database (Denmark)

nrc762, nrc762

2016-01-01

Numerical studies by Wójs, Yi, and Quinn have suggested that an unconventional fractional quantum Hall effect is plausible at filling factors ν=1/3 and 1/5, provided the interparticle interaction has an unusual form for which the energy of two fermions in the relative angular momentum three channel...... as fractional quantum Hall effect of electrons at ν=4/11, 4/13, 5/13, and 5/17. I investigate in this article the nature of the fractional quantum Hall states at ν=4/5, 5/7, 6/17, and 6/7, which correspond to composite fermions at ν∗=4/3, 5/3, and 6/5, and find that all these fractional quantum Hall states...... are conventional. The underlying reason is that the interaction between composite fermions depends substantially on both the number and the direction of the vortices attached to the electrons. I also study in detail the states with different spin polarizations at 6/17 and 6/7 and predict the critical Zeeman...

Tunable arbitrary unitary transformer based on multiple sections of multicore fibers with phase control.

Science.gov (United States)

Zhou, Junhe; Wu, Jianjie; Hu, Qinsong

2018-02-05

In this paper, we propose a novel tunable unitary transformer, which can achieve arbitrary discrete unitary transforms. The unitary transformer is composed of multiple sections of multi-core fibers with closely aligned coupled cores. Phase shifters are inserted before and after the sections to control the phases of the waves in the cores. A simple algorithm is proposed to find the optimal phase setup for the phase shifters to realize the desired unitary transforms. The proposed device is fiber based and is particularly suitable for the mode division multiplexing systems. A tunable mode MUX/DEMUX for a three-mode fiber is designed based on the proposed structure.

Fermion-number violation in regularizations that preserve fermion-number symmetry

Science.gov (United States)

Golterman, Maarten; Shamir, Yigal

2003-01-01

There exist both continuum and lattice regularizations of gauge theories with fermions which preserve chiral U(1) invariance (“fermion number”). Such regularizations necessarily break gauge invariance but, in a covariant gauge, one recovers gauge invariance to all orders in perturbation theory by including suitable counterterms. At the nonperturbative level, an apparent conflict then arises between the chiral U(1) symmetry of the regularized theory and the existence of ’t Hooft vertices in the renormalized theory. The only possible resolution of the paradox is that the chiral U(1) symmetry is broken spontaneously in the enlarged Hilbert space of the covariantly gauge-fixed theory. The corresponding Goldstone pole is unphysical. The theory must therefore be defined by introducing a small fermion-mass term that breaks explicitly the chiral U(1) invariance and is sent to zero after the infinite-volume limit has been taken. Using this careful definition (and a lattice regularization) for the calculation of correlation functions in the one-instanton sector, we show that the ’t Hooft vertices are recovered as expected.

Quasinormal modes, stability analysis and absorption cross section for 4-dimensional topological Lifshitz black hole

International Nuclear Information System (INIS)

Gonzalez, P.A.; Moncada, Felipe; Vasquez, Yerko

2012-01-01

We study scalar perturbations in the background of a topological Lifshitz black hole in four dimensions. We compute analytically the quasinormal modes and from these modes we show that topological Lifshitz black hole is stable. On the other hand, we compute the reflection and transmission coefficients and the absorption cross section and we show that there is a range of modes with high angular momentum which contributes to the absorption cross section in the low frequency limit. Furthermore, in this limit, we show that the absorption cross section decreases if the scalar field mass increases, for a real scalar field mass. (orig.)

Quasinormal modes, stability analysis and absorption cross section for 4-dimensional topological Lifshitz black hole

Energy Technology Data Exchange (ETDEWEB)

Gonzalez, P.A. [Universidad Central de Chile, Escuela de Ingenieria Civil en Obras Civiles, Facultad de Ciencias Fisicas y Matematicas, Santiago (Chile); Universidad Diego Portales, Santiago (Chile); Moncada, Felipe; Vasquez, Yerko [Universidad de La Frontera, Departamento de Ciencias Fisicas, Facultad de Ingenieria, Ciencias y Administracion, Temuco (Chile)

2012-12-15

We study scalar perturbations in the background of a topological Lifshitz black hole in four dimensions. We compute analytically the quasinormal modes and from these modes we show that topological Lifshitz black hole is stable. On the other hand, we compute the reflection and transmission coefficients and the absorption cross section and we show that there is a range of modes with high angular momentum which contributes to the absorption cross section in the low frequency limit. Furthermore, in this limit, we show that the absorption cross section decreases if the scalar field mass increases, for a real scalar field mass. (orig.)

Dynamical triangulated fermionic surfaces

International Nuclear Information System (INIS)

Ambjoern, J.; Varsted, S.

1990-12-01

We perform Monte Carlo simulations of randomly triangulated random surfaces which have fermionic world-sheet scalars θ i associated with each vertex i in addition to the usual bosonic world-sheet scalar χ i μ . The fermionic degrees of freedom force the internal metrics of the string to be less singular than the internal metric of the pure bosonic string. (orig.)

Heavy fermion materials

International Nuclear Information System (INIS)

Smith, J.L.; Cooke, D.W.

1986-01-01

The heavy-fermion ground state occurs in a few select metallic compounds as a result of interactions between f-electron and conduction-electron spins. A characteristically large electronic heat capacity at low temperature indicates that the effective electron mass of these materials is more than two orders of magnitude greater than that expected for a free-electron metal. This heavy-fermion ground state can become superconducting or antiferromagnetic, exhibiting very unusual properties. These materials and the role of muon spin rotation in their study are briefly discussed

Four-fermion interaction near four dimensions

International Nuclear Information System (INIS)

Zinn-Justin, J.

1991-01-01

A large class of models with four-fermion interactions is known to be renormalizable and asymptotically free in two dimensions. It has been noticed very early, in the example of the U(N)-invariant Gross-Neveu model and within the framework of the 1/N expansion, that then these models behave also like renormalizable models in higher dimensions. Some of them are thus natural candidates for composite models of scalar particles like for example the Higgs boson. An important question, however, has to be answered: Are these models more predictive, in four dimensions, than the effective models containing the bosons explicitly? We shall show here that, like for the non-linear σ-model which has been investigated earlier, the answer, at least in some perturbative sense, is negative for a large class of models. The reason can be easily understood: These models are more short-distance sensitive than normal renormalizable models. The new parameters are hidden in the cut-off procedure. In particular in some models the fermions receive masses by spontaneous chiral symmetry breaking. The property that ratio of fermion and boson masses can be predicted is simply a consequence of the IR freedom of both type of models and the natural assumption that coupling constants have generic values at the cut-off scale. We shall consider in this article for definiteness the Gross-Neveu model but it will be clear that the arguments are rather general. (orig.)

The bosonic mother of fermionic D-branes

OpenAIRE

Chattaraputi, Auttakit; Englert, Francois; Houart, Laurent; Taormina, Anne

2002-01-01

We extend the search for fermionic subspaces of the bosonic string compactified on E8 X SO(16) lattices to include all fermionic D-branes. This extension constraints the truncation procedure previously proposed and relates the fermionic strings, supersymmetric or not, to the global structure of the SO(16) group. The specific properties of all the fermionic D-branes are found to be encoded in its universal covering, whose maximal toroid defines the configuration space torus of their mother bos...

Remarks on fermion-number violation and premature unitarization in high-energy instanton-induced scattering

International Nuclear Information System (INIS)

Maggiore, M.; Shifman, M.

1993-01-01

We critically discuss recent works in which the premature unitarization mechanism is studied with the inclusion of non-nearest-neighbor interactions or beyond leading order in the energy. We also point out that the nonperturbative valley method gives inconsistent results when applied to fermion-number-violating amplitudes, and we argue that, independently of the mechanism of premature unitarization, the nonperturbative amplitudes which violate the fermion number are always exponentially suppressed

Super boson-fermion correspondence

International Nuclear Information System (INIS)

Kac, V.G.; Leur van de, J.W.

1987-01-01

Since the pioneering work of Skyrme, the boson-fermion correspondence has been playing an increasingly important role in 2-dimensional quantum field theory. More recently, it has become an important ingredient in the work of the Kyoto school on the KP hierarchy of soliton equations. In the present paper we establish a super boson-fermion correspondence, having in mind its applications to super KP hierarchies

Fermion-scalar conformal blocks

Energy Technology Data Exchange (ETDEWEB)

Iliesiu, Luca [Joseph Henry Laboratories, Princeton University,Washington Road, Princeton, NJ 08544 (United States); Kos, Filip [Department of Physics, Yale University,217 Prospect Street, New Haven, CT 06520 (United States); Poland, David [Department of Physics, Yale University,217 Prospect Street, New Haven, CT 06520 (United States); School of Natural Sciences, Institute for Advanced Study,1 Einstein Dr, Princeton, New Jersey 08540 (United States); Pufu, Silviu S. [Joseph Henry Laboratories, Princeton University,Washington Road, Princeton, NJ 08544 (United States); Simmons-Duffin, David [School of Natural Sciences, Institute for Advanced Study,1 Einstein Dr, Princeton, New Jersey 08540 (United States); Yacoby, Ran [Joseph Henry Laboratories, Princeton University,Washington Road, Princeton, NJ 08544 (United States)

2016-04-13

We compute the conformal blocks associated with scalar-scalar-fermion-fermion 4-point functions in 3D CFTs. Together with the known scalar conformal blocks, our result completes the task of determining the so-called ‘seed blocks’ in three dimensions. Conformal blocks associated with 4-point functions of operators with arbitrary spins can now be determined from these seed blocks by using known differential operators.

Unitary relation for the time-dependent SU(1,1) systems

International Nuclear Information System (INIS)

Song, Dae-Yup

2003-01-01

The system whose Hamiltonian is a linear combination of the generators of SU(1,1) group with time-dependent coefficients is studied. It is shown that there is a unitary relation between the system and a system whose Hamiltonian is simply proportional to the generator of the compact subgroup of SU(1,1). The unitary relation is described by the classical solutions of a time-dependent (harmonic) oscillator. Making use of the relation, the wave functions satisfying the Schroedinger equation are given, for a general unitary representation, in terms of the matrix elements of a finite group transformation (Bargmann function). The wave functions of the harmonic oscillator with an inverse-square potential is studied in detail, and it is shown that through an integral, the model provides a way of deriving the Bargmann function for the representation of positive discrete series of SU(1,1)

Lattice degeneracies of geometric fermions

International Nuclear Information System (INIS)

Raszillier, H.

1983-05-01

We give the minimal numbers of degrees of freedom carried by geometric fermions on all lattices of maximal symmetries in d = 2, 3, and 4 dimensions. These numbers are lattice dependent, but in the (free) continuum limit, part of the degrees of freedom have to escape to infinity by a Wilson mechanism built in, and 2sup(d) survive for any lattice. On self-reciprocal lattices we compare the minimal numbers of degrees of freedom of geometric fermions with the minimal numbers of naive fermions on these lattices and argue that these numbers are equal. (orig.)

On the reconstruction of a unitary matrix from its moduli. Existence of continuous ambiguities

International Nuclear Information System (INIS)

Auberson, G.

1989-01-01

It is shown that, for an n x n unitary matrix with n ≥ 4, the knowledge of the moduli of its elements is not always sufficient to determine this matrix up to 'trivial' or 'discrete' ambiguities. Using a parametrization a la Kobayashi-Maskawa in the case n=4, we exhibit various configurations of the moduli for which a continuous ambiguity appears (i.e., some non-trivial phase remains free). (orig.)

Magnetic Majorana Fermions

Science.gov (United States)

Moessner, Roderich

Condensed matter systems provide emergent mini-universes in which quasiparticles may exist which do not correspond to any experimentally detected elementary particle. Topological quantum materials have been particularly productive in this regard, with the present search focussing on Majorana fermions, known theoretically already for decades. Here, we discuss manifestations of magnetic Majorana fermions in the Kitaev model. We place particular emphasis on their fate when perturbations, such as Heisenberg terms, are added to the ideal model system, and address experimental signatures of their vestiges in phases adjacent to the spin liquid.

Superconductivity in mixed boson-fermion systems

International Nuclear Information System (INIS)

Ioffe, L.; Larkin, A.I.; Ovchinnikov, Yu.N.; Yu, L.

1989-12-01

The superconductivity of mixed boson-fermion systems is studied using a simple boson-fermion transformation model. The critical temperature of the superconducting transition is calculated over a wide range of the narrow boson band position relative to the Fermi level. The BCS scenario and boson condensation picture are recovered in two limiting cases of high and low positions of boson band, respectively, with modifications due to boson-fermion interaction. (author). 11 refs

Three mirror pairs of fermion families

International Nuclear Information System (INIS)

Montvay, I.

1988-01-01

A simple model with three mirror pairs of fermion families is considered which allows for a substantial mixing between the mirror fermion partners without conflicting with known phenomenology. (orig.)

Optimal unitary dilation for bosonic Gaussian channels

International Nuclear Information System (INIS)

Caruso, Filippo; Eisert, Jens; Giovannetti, Vittorio; Holevo, Alexander S.

2011-01-01

A general quantum channel can be represented in terms of a unitary interaction between the information-carrying system and a noisy environment. In this paper the minimal number of quantum Gaussian environmental modes required to provide a unitary dilation of a multimode bosonic Gaussian channel is analyzed for both pure and mixed environments. We compute this quantity in the case of pure environment corresponding to the Stinespring representation and give an improved estimate in the case of mixed environment. The computations rely, on one hand, on the properties of the generalized Choi-Jamiolkowski state and, on the other hand, on an explicit construction of the minimal dilation for arbitrary bosonic Gaussian channel. These results introduce a new quantity reflecting ''noisiness'' of bosonic Gaussian channels and can be applied to address some issues concerning transmission of information in continuous variables systems.

Alternative to domain wall fermions

International Nuclear Information System (INIS)

Neuberger, H.

2002-01-01

An alternative to commonly used domain wall fermions is presented. Some rigorous bounds on the condition number of the associated linear problem are derived. On the basis of these bounds and some experimentation it is argued that domain wall fermions will in general be associated with a condition number that is of the same order of magnitude as the product of the condition number of the linear problem in the physical dimensions by the inverse bare quark mass. Thus, the computational cost of implementing true domain wall fermions using a single conjugate gradient algorithm is of the same order of magnitude as that of implementing the overlap Dirac operator directly using two nested conjugate gradient algorithms. At a cost of about a factor of two in operation count it is possible to make the memory usage of direct implementations of the overlap Dirac operator independent of the accuracy of the approximation to the sign function and of the same order as that of standard Wilson fermions

Interacting fermions in two dimensions: Beyond the perturbation theory

International Nuclear Information System (INIS)

Gangadharaiah, S.; Maslov, D.L.; Chubukov, A.V.; Glazman, L.I.

2005-05-01

We consider a system of 2D fermions with short-range interaction. A straightforward perturbation theory is shown to be ill-defined even for an infinitesimally weak interaction, as the perturbative series for the self-energy diverges near the mass shell. We show that the divergences result from the interaction of fermions with the zero-sound collective mode. By re-summing the most divergent diagrams, we obtain a closed form of the self-energy near the mass shell. The spectral function exhibits a threshold feature at the onset of the emission of the zero-sound waves. We also show that the interaction with the zero sound does not affect a non- analytic, T 2 -part of the specific heat. (author)

Two-dimensional confinement of heavy fermions

International Nuclear Information System (INIS)

Shishido, Hiroaki; Shibauchi, Takasada; Matsuda, Yuji; Terashima, Takahito

2010-01-01

Metallic systems with the strongest electron correlations are realized in certain rare-earth and actinide compounds whose physics are dominated by f-electrons. These materials are known as heavy fermions, so called because the effective mass of the conduction electrons is enhanced via correlation effects up to as much as several hundreds times the free electron mass. To date the electronic structure of all heavy-fermion compounds is essentially three-dimensional. Here we report on the first realization of a two-dimensional heavy-fermion system, where the dimensionality is adjusted in a controllable fashion by fabricating heterostructures using molecular beam epitaxy. The two-dimensional heavy fermion system displays striking deviations from the standard Fermi liquid low-temperature electronic properties. (author)

Fermion tunneling from higher-dimensional black holes

International Nuclear Information System (INIS)

Lin Kai; Yang Shuzheng

2009-01-01

Via the semiclassical approximation method, we study the 1/2-spin fermion tunneling from a higher-dimensional black hole. In our work, the Dirac equations are transformed into a simple form, and then we simplify the fermion tunneling research to the study of the Hamilton-Jacobi equation in curved space-time. Finally, we get the fermion tunneling rates and the Hawking temperatures at the event horizon of higher-dimensional black holes. We study fermion tunneling of a higher-dimensional Schwarzschild black hole and a higher-dimensional spherically symmetric quintessence black hole. In fact, this method is also applicable to the study of fermion tunneling from four-dimensional or lower-dimensional black holes, and we will take the rainbow-Finsler black hole as an example in order to make the fact explicit.

arXiv Charged Fermions Below 100 GeV

CERN Document Server

Egana-Ugrinovic, Daniel; Ruderman, Joshua T.

2018-05-03

How light can a fermion be if it has unit electric charge? We revisit the lore that LEP robustly excludes charged fermions lighter than about 100 GeV. We review LEP chargino searches, and find them to exclude charged fermions lighter than 90 GeV, assuming a higgsino-like cross section. However, if the charged fermion couples to a new scalar, destructive interference among production channels can lower the LEP cross section by a factor of 3. In this case, we find that charged fermions as light as 75 GeV can evade LEP bounds, while remaining consistent with constraints from the LHC. As the LHC collects more data, charged fermions in the 75–100 GeV mass range serve as a target for future monojet and disappearing track searches.

Propagator of the lattice domain wall fermion and the staggered fermion

International Nuclear Information System (INIS)

Furui, S.

2009-01-01

We calculate the propagator of the domain wall fermion (DWF) of the RBC/UKQCD collaboration with 2 + 1 dynamical flavors of 16 3 x 32 x 16 lattice in Coulomb gauge, by applying the conjugate gradient method. We find that the fluctuation of the propagator is small when the momenta are taken along the diagonal of the 4-dimensional lattice. Restricting momenta in this momentum region, which is called the cylinder cut, we compare the mass function and the running coupling of the quark-gluon coupling a s,g1 (q) with those of the staggered fermion of the MILC collaboration in Landau gauge. In the case of DWF, the ambiguity of the phase of the wave function is adjusted such that the overlap of the solution of the conjugate gradient method and the plane wave at the source becomes real. The quark-gluon coupling a s,g1 (q) of the DWF in the region q > 1.3 GeV agrees with ghost-gluon coupling a s (q) that we measured by using the configuration of the MILC collaboration, i.e., enhancement by a factor (1 + c/q 2 ) with c ∼ 2.8 GeV 2 on the pQCD result. In the case of staggered fermion, in contrast to the ghost-gluon coupling a s (q) in Landau gauge which showed infrared suppression, the quark-gluon coupling a s,g1 (q) in the infrared region increases monotonically as q → 0. Above 2 GeV, the quark-gluon coupling a s,g1 (q) of staggered fermion calculated by naive crossing becomes smaller than that of DWF, probably due to the complex phase of the propagator which is not connected with the low energy physics of the fermion taste. An erratum to this article can be found at http://dx.doi.org/10.1007/s00601-009-0053-4. (author)

Fermionic topological quantum states as tensor networks

Science.gov (United States)

Wille, C.; Buerschaper, O.; Eisert, J.

2017-06-01

Tensor network states, and in particular projected entangled pair states, play an important role in the description of strongly correlated quantum lattice systems. They do not only serve as variational states in numerical simulation methods, but also provide a framework for classifying phases of quantum matter and capture notions of topological order in a stringent and rigorous language. The rapid development in this field for spin models and bosonic systems has not yet been mirrored by an analogous development for fermionic models. In this work, we introduce a tensor network formalism capable of capturing notions of topological order for quantum systems with fermionic components. At the heart of the formalism are axioms of fermionic matrix-product operator injectivity, stable under concatenation. Building upon that, we formulate a Grassmann number tensor network ansatz for the ground state of fermionic twisted quantum double models. A specific focus is put on the paradigmatic example of the fermionic toric code. This work shows that the program of describing topologically ordered systems using tensor networks carries over to fermionic models.

Phenomenology of colour exotic fermions

International Nuclear Information System (INIS)

Luest, D.

1986-01-01

The authors discuss the phenomenological consequences of a dynamical scenario according to which the electroweak symmetry breaking and generation of fermion masses is due to fermions that transform under high colour representations. Particular emphasis is given to the predictions for rare processes and to the spectrum of high colour boundstates. (Auth.)

Universal Superspace Unitary Operator and Nilpotent (Anti-)Dual-BRST Symmetries: Superfield Formalism

International Nuclear Information System (INIS)

Malik, R. P.; Srinivas, N.; Bhanja, T.

2016-01-01

We exploit the key concepts of the augmented version of superfield approach to Becchi-Rouet-Stora-Tyutin (BRST) formalism to derive the superspace (SUSP) dual unitary operator and its Hermitian conjugate and demonstrate their utility in the derivation of the nilpotent and absolutely anticommuting (anti-)dual-BRST symmetry transformations for a set of interesting models of the Abelian 1-form gauge theories. These models are the one (0+1)-dimensional (1D) rigid rotor and modified versions of the two (1+1)-dimensional (2D) Proca as well as anomalous gauge theories and 2D model of a self-dual bosonic field theory. We show the universality of the SUSP dual unitary operator and its Hermitian conjugate in the cases of all the Abelian models under consideration. These SUSP dual unitary operators, besides maintaining the explicit group structure, provide the alternatives to the dual horizontality condition (DHC) and dual gauge invariant restrictions (DGIRs) of the superfield formalism. The derivations of the dual unitary operators and corresponding (anti-)dual-BRST symmetries are completely novel results in our present investigation.

Search for Majorana fermions in topological superconductors.

Energy Technology Data Exchange (ETDEWEB)

Pan, Wei [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Shi, Xiaoyan [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hawkins, Samuel D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Klem, John Frederick [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2014-10-01

The goal of this project is to search for Majorana fermions (a new quantum particle) in a topological superconductor (a new quantum matter achieved in a topological insulator proximitized by an s-wave superconductor). Majorana fermions (MFs) are electron-like particles that are their own anti-particles. MFs are shown to obey non-Abelian statistics and, thus, can be harnessed to make a fault-resistant topological quantum computer. With the arrival of topological insulators, novel schemes to create MFs have been proposed in hybrid systems by combining a topological insulator with a conventional superconductor. In this LDRD project, we will follow the theoretical proposals to search for MFs in one-dimensional (1D) topological superconductors. 1D topological superconductor will be created inside of a quantum point contact (with the metal pinch-off gates made of conventional s-wave superconductors such as niobium) in a two-dimensional topological insulator (such as inverted type-II InAs/GaSb heterostructure).

Fermions in nonrelativistic AdS/CFT correspondence

International Nuclear Information System (INIS)

Akhavan, Amin; Alishahiha, Mohsen; Davody, Ali; Vahedi, Ali

2009-01-01

We extend the nonrelativistic AdS/CFT correspondence to the fermionic fields. In particular, we study the two point function of a fermionic operator in nonrelativistic CFTs by making use of a massive fermion propagating in geometries with Schroedinger group isometry. Although the boundary of the geometries with Schroedinger group isometry differ from that in AdS geometries where the dictionary of AdS/CFT is established, using the general procedure of AdS/CFT correspondence, we see that the resultant two point function has the expected form for fermionic operators in nonrelativistic CFTs, though a nontrivial regularization may be needed.

Quasinormal modes and absorption probabilities of spin-3 /2 fields in D -dimensional Reissner-Nordström black hole spacetimes

Science.gov (United States)

Chen, C.-H.; Cho, H. T.; Cornell, A. S.; Harmsen, G.; Ngcobo, X.

2018-01-01

In this paper we consider spin-3 /2 fields in a D -dimensional Reissner-Nordström black hole spacetime. As these spacetimes are not Ricci flat, it is necessary to modify the covariant derivative to the supercovariant derivative, by including terms related to the background electromagnetic fields, so as to maintain the gauge symmetry. Using this supercovariant derivative we arrive at the corresponding Rarita-Schwinger equation in a charged black hole background. As in our previous works, we exploit the spherical symmetry of the spacetime and use the eigenspinor vectors on an N sphere to derive the radial equations for both nontransverse-traceless (non-TT) modes and TT modes. We then determine the quasinormal mode and absorption probabilities of the associated gauge-invariant variables using the WKB approximation and the asymptotic iteration method. We then concentrate on how these quantities change with the charge of the black hole, especially when they reach the extremal limits.

Cogeneration Power Plants: a Proposed Methodology for Unitary Production Cost

International Nuclear Information System (INIS)

Metalli, E.

2009-01-01

A new methodology to evaluate unitary energetic production costs in the cogeneration power plants is proposed. This methodology exploits the energy conversion factors fixed by Italian Regulatory Authority for Electricity and Gas. So it allows to settle such unitary costs univocally for a given plant, without assigning them a priori subjective values when there are two or more energy productions at the same time. Moreover the proposed methodology always ensures positive values for these costs, complying with the total generation cost balance equation. [it

Heavy fermion and actinide materials

International Nuclear Information System (INIS)

1993-01-01

During this period, 1/N expansions have been systematically applied to the calculation of the properties of highly correlated electron systems. These studies include examinations of (a) the class of materials known as heavy fermion semi-conductors, (b) the high energy spectra of heavy fermion systems, and (c) the doped oxide superconductors

Fermion fractionization and index theorem

International Nuclear Information System (INIS)

Hirayama, Minoru; Torii, Tatsuo

1982-01-01

The relation between the fermion fractionization and the Callias-Bott-Seeley index theorem for the Dirac operator in the open space of odd dimension is clarified. Only the case of one spatial dimension is discussed in detail. Sum rules for the expectation values of various quantities in fermion-fractionized configurations are derived. (author)

Bethe-Salpeter equation for fermion-antifermion system in the ladder approximation

International Nuclear Information System (INIS)

Fukui, Ichio; Seto, Noriaki; Yoshida, Toshihiro.

1977-01-01

The Bethe-Salpeter (B-S) equation is important for studying hadron physics. Especially intensive investigation on the fermion-antifermion B-S equation is indispensable for the phenomenological studies of hardrons. However, many components of the B-S amplitude and the Wick-rotated integral kernel of non-Fredholm type have prevented from knowing details the solutions even in the ladder approximation. Some particular solutions are known in case of the vanishing four-momenta of bound states. The B-S equation for the bound state of fermion-anti-fermion system interacting through vector (axial-vector) particle exchange was studied in the ladder approximation with Feynman gauge. The reduced equations were obtained for suitably decomposed amplitude, and it is shown that, in the S-wave case, the coupled equations separate into two parts. In the nonrelativistic limit, large components of the amplitude satisfy the Wick-Cutkosky equation, and small components are expressed in terms of the large ones. Equations are derived for the equal-time amplitudes. (Kobatake, H.)

Composite fermions in the quantum Hall effect

International Nuclear Information System (INIS)

Johnson, B.L.; Kirczenow, G.

1997-01-01

The quantum Hall effect and associated quantum transport phenomena in low-dimensional systems have been the focus of much attention for more than a decade. Recent theoretical development of interesting quasiparticles - 'composite fermions' - has led to significant advances in understanding and predicting the behaviour of two-dimensional electron systems under high transverse magnetic fields. Composite fermions may be viewed as fermions carrying attached (fictitious) magnetic flux. Here we review models of the integer and fractional quantum Hall effects, including the development of a unified picture of the integer and fractional effects based upon composite fermions. The composite fermion picture predicts remarkable new physics: the formation of a Fermi surface at high magnetic fields, and anomalous ballistic transport, thermopower, and surface acoustic wave behaviour. The specific theoretical predictions of the model, as well as the body of experimental evidence for these phenomena are reviewed. We also review recent edge-state models for magnetotransport in low-dimensional devices based on the composite fermion picture. These models explain the fractional quantum Hall effect and transport phenomena in nanoscale devices in a unified framework that also includes edge state models of the integer quantum Hall effect. The features of the composite fermion edge-state model are compared and contrasted with those of other recent edge-state models of the fractional quantum Hall effect. (author)

The continuum limit of causal fermion systems from Planck scale structures to macroscopic physics

CERN Document Server

Finster, Felix

2016-01-01

This monograph introduces the basic concepts of the theory of causal fermion systems, a recent approach to the description of fundamental physics. The theory yields quantum mechanics, general relativity and quantum field theory as limiting cases and is therefore a candidate for a unified physical theory. From the mathematical perspective, causal fermion systems provide a general framework for describing and analyzing non-smooth geometries and "quantum geometries". The dynamics is described by a novel variational principle, called the causal action principle. In addition to the basics, the book provides all the necessary mathematical background and explains how the causal action principle gives rise to the interactions of the standard model plus gravity on the level of second-quantized fermionic fields coupled to classical bosonic fields. The focus is on getting a mathematically sound connection between causal fermion systems and physical systems in Minkowski space. The book is intended for graduate students e...

Fermionic phase transition induced by the effective impurity in holography

Energy Technology Data Exchange (ETDEWEB)

Fang, Li-Qing [IFSA Collaborative Innovation Center, Department of Physics and Astronomy,Shanghai Jiao Tong University, Shanghai 200240 (China); School of Physics and Electronic Information, Shangrao Normal University,Shangrao 334000 (China); Kuang, Xiao-Mei [Department of Physics, National Technical University of Athens,GR-15780 Athens (Greece); Instituto de Física, Pontificia Universidad Católica de Valparaíso,Casilla 4059, Valparaíso (Chile); Wang, Bin [IFSA Collaborative Innovation Center, Department of Physics and Astronomy,Shanghai Jiao Tong University, Shanghai 200240 (China); Wu, Jian-Pin [Institute of Gravitation and Cosmology, Department of Physics,School of Mathematics and Physics, Bohai University, Jinzhou 121013 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,Chinese Academy of Sciences, Beijing 100190 (China)

2015-11-20

We investigate the holographic fermionic phase transition induced by the effective impurity in holography, which is introduced by massless scalar fields in Einstein-Maxwell-massless scalar gravity. We obtain a phase diagram in (α,T) plane separating the Fermi liquid phase and the non-Fermi liquid phase.

The Fermionic Signature Operator and Hadamard States in the Presence of a Plane Electromagnetic Wave

Science.gov (United States)

Finster, Felix; Reintjes, Moritz

2017-05-01

We give a non-perturbative construction of a distinguished state for the quantized Dirac field in Minkowski space in the presence of a time-dependent external field of the form of a plane electromagnetic wave. By explicit computation of the fermionic signature operator, it is shown that the Dirac operator has the strong mass oscillation property. We prove that the resulting fermionic projector state is a Hadamard state.

Finite boson mappings of fermion systems

International Nuclear Information System (INIS)

Johnson, C.W.; Ginocchio, J.N.

1994-01-01

We discuss a general mapping of fermion pairs to bosons that preserves Hermitian conjugation, with an eye towards producing finite and usable boson Hamiltonians that approximate well the low-energy dynamics of a fermion Hamiltonian

Fermion current algebras and Schwinger terms in (3+1)-dimensions

International Nuclear Information System (INIS)

Langmann, E.

1994-01-01

We discuss the restricted linear group in infinite dimensions modeled by the Schatten class of rank 2p=4 which contains the (3+1)-dimensional analogs of the loop groups and is closely related to Yang-Mills theory with fermions in (3+1)-dimensions. We give an alternative to the construction of the ''highest weight'' representation of this group found by Mickelsson and Rajeev. Our approach is close to quantum field theory, with the elements of this group regarded as Bogoliubov transformations for fermions in an external Yang-Mills field. Though these cannot be unitarily implemented in the physically relevant representation of the fermion field algebra, we argue that they can be implemented by sesquilinear forms, and that there is a (regularized) product of forms providing an appropriate group structure. On the Lie algebra level, this gives an explicit, non-perturbative construction of fermion current algebras in (3+1) space-time dimensions which explicitly shows that the ''wave function renormalization'' required for a consistent definition of the currents and their Lie bracket naturally leads to the Schwinger term identical with the Mickelsson-Rajeev cocycle. Though the explicit form of the Schwinger term is given only for the case p=2, our arguments apply also to the restricted linear groups modeled by Schatten classes of rank 2p=6, 8, .. corresponding to current algebras in (d+1)-dimensions, d=5, 7, .. (orig.)

Structural aspects of the fermion-boson mapping in two-dimensional gauge and anomalous gauge theories with massive fermions

International Nuclear Information System (INIS)

Belvedere, L.V.; Souza Dutra, A. de; Natividade, C.P.; Queiroz, A.F. de

2002-01-01

Using a synthesis of the functional integral and operator approaches we discuss the fermion-boson mapping and the role played by the Bose field algebra in the Hilbert space of two-dimensional gauge and anomalous gauge field theories with massive fermions. In QED 2 with quartic self-interaction among massive fermions, the use of an auxiliary vector field introduces a redundant Bose field algebra that should not be considered as an element of the intrinsic algebraic structure defining the model. In anomalous chiral QED 2 with massive fermions the effect of the chiral anomaly leads to the appearance in the mass operator of a spurious Bose field combination. This phase factor carries no fermion selection rule and the expected absence of Θ-vacuum in the anomalous model is displayed from the operator solution. Even in the anomalous model with massive Fermi fields, the introduction of the Wess-Zumino field replicates the theory, changing neither its algebraic content nor its physical content

Nonequilibrium fermion production in quantum field theory

International Nuclear Information System (INIS)

Pruschke, Jens

2010-01-01

The creation of matter in the early universe or in relativistic heavy-ion collisions is inevitable connected to nonequilibrium physics. One of the key challenges is the explanation of the corresponding thermalization process following nonequilibrium instabilities. The role of fermionic quantum fields in such scenarios is discussed in the literature by using approximations of field theories which neglect important quantum corrections. This thesis goes beyond such approximations. A quantum field theory where scalar bosons interact with Dirac fermions via a Yukawa coupling is analyzed in the 2PI effective action formalism. The chosen approximation allows for a correct description of the dynamics including nonequilibrium instabilities. In particular, fermion-boson loop corrections allow to study the interaction of fermions with large boson fluctuations. The applied initial conditions generate nonequilibrium instabilities like parametric resonance or spinodal instabilities. The equations of motion for correlation functions are solved numerically and major characteristics of the fermion dynamics are described by analytical solutions. New mechanisms for the production of fermions are found. Simulations in the case of spinodal instability show that unstable boson fluctuations induce exponentially growing fermion modes with approximately the same growth rate. If the unstable regime lasts long enough a thermalization of the infrared part of the fermion occupation number occurs on time scales much shorter than the time scale on which bosonic quantum fields thermalize. Fermions acquire an excess of occupation in the ultraviolet regime compared to a Fermi-Dirac statistic characterized by a power-law with exponent two. The fermion production mechanism via parametric resonance is found to be most efficient after the instability ends. Quantum corrections then provide a very efficient particle creation mechanism which is interpreted as an amplification of decay processes. The ratio

Nonequilibrium fermion production in quantum field theory

Energy Technology Data Exchange (ETDEWEB)

Pruschke, Jens

2010-06-16

The creation of matter in the early universe or in relativistic heavy-ion collisions is inevitable connected to nonequilibrium physics. One of the key challenges is the explanation of the corresponding thermalization process following nonequilibrium instabilities. The role of fermionic quantum fields in such scenarios is discussed in the literature by using approximations of field theories which neglect important quantum corrections. This thesis goes beyond such approximations. A quantum field theory where scalar bosons interact with Dirac fermions via a Yukawa coupling is analyzed in the 2PI effective action formalism. The chosen approximation allows for a correct description of the dynamics including nonequilibrium instabilities. In particular, fermion-boson loop corrections allow to study the interaction of fermions with large boson fluctuations. The applied initial conditions generate nonequilibrium instabilities like parametric resonance or spinodal instabilities. The equations of motion for correlation functions are solved numerically and major characteristics of the fermion dynamics are described by analytical solutions. New mechanisms for the production of fermions are found. Simulations in the case of spinodal instability show that unstable boson fluctuations induce exponentially growing fermion modes with approximately the same growth rate. If the unstable regime lasts long enough a thermalization of the infrared part of the fermion occupation number occurs on time scales much shorter than the time scale on which bosonic quantum fields thermalize. Fermions acquire an excess of occupation in the ultraviolet regime compared to a Fermi-Dirac statistic characterized by a power-law with exponent two. The fermion production mechanism via parametric resonance is found to be most efficient after the instability ends. Quantum corrections then provide a very efficient particle creation mechanism which is interpreted as an amplification of decay processes. The ratio

Stability under scalar perturbations and quasinormal modes of 4D Einstein-Born-Infeld dilaton spacetime. Exact spectrum

International Nuclear Information System (INIS)

Destounis, Kyriakos; Panotopoulos, Grigoris; Rincon, Angel

2018-01-01

We study the stability under scalar perturbations, and we compute the quasinormal modes of the Einstein-Born-Infeld dilaton spacetime in 1 + 3 dimensions. Solving the full radial equation in terms of hypergeometric functions, we provide an exact analytical expression for the spectrum. We find that the frequencies are purely imaginary, and we confirm our results by computing them numerically. Although the scalar field that perturbs the black hole is electrically neutral, an instability similar to that seen in charged scalar perturbations of the Reissner-Nordstroem black hole is observed. (orig.)

Stability under scalar perturbations and quasinormal modes of 4D Einstein-Born-Infeld dilaton spacetime. Exact spectrum

Energy Technology Data Exchange (ETDEWEB)

Destounis, Kyriakos; Panotopoulos, Grigoris [Universidade de Lisboa, Centro Multidisciplinar de Astrofisica, Instituto Superior Tecnico, Lisbon (Portugal); Rincon, Angel [Pontificia Universidad Catolica de Chile, Instituto de Fisica, Santiago (Chile)

2018-02-15

We study the stability under scalar perturbations, and we compute the quasinormal modes of the Einstein-Born-Infeld dilaton spacetime in 1 + 3 dimensions. Solving the full radial equation in terms of hypergeometric functions, we provide an exact analytical expression for the spectrum. We find that the frequencies are purely imaginary, and we confirm our results by computing them numerically. Although the scalar field that perturbs the black hole is electrically neutral, an instability similar to that seen in charged scalar perturbations of the Reissner-Nordstroem black hole is observed. (orig.)

Fermion condensation: a strange idea successfully explaining behaviour of numerous objects in nature

International Nuclear Information System (INIS)

Shaginyan, V.R.; Amusia, M.Ya.; Popov, K.G.

2010-01-01

A theory of fermion condensation quantum phase transition, preserving the extended quasiparticles paradigm and intimately related to the unlimited growth of the effective mass as a function of the temperature, magnetic field, etc., is capable to resolve the problem. We discuss the construction of the theory and show that it delivers theoretical explanations of the vast majority of experimental results in strongly correlated systems such as heavy-fermion metals and quasi-two dimensional Fermi systems. Our analysis is placed in the context of recent salient experimental results. Our calculations of the non-Fermi liquid behavior, the scales, and thermodynamic and transport properties are in good agreement with the heat capacity, magnetization, longitudinal magnetoresistance, and magnetic entropy obtained in remarkable measurements on the heavy-fermion metal YbRh 2 Si 2 .

Causal fermion systems as a candidate for a unified physical theory

Science.gov (United States)

Finster, Felix; Kleiner, Johannes

2015-07-01

The theory of causal fermion systems is an approach to describe fundamental physics. Giving quantum mechanics, general relativity and quantum field theory as limiting cases, it is a candidate for a unified physical theory. We here give a non-technical introduction.

Lattice fermions

Energy Technology Data Exchange (ETDEWEB)

Randjbar-Daemi, S

1995-12-01

The so-called doubling problem in the lattice description of fermions led to a proof that under certain circumstances chiral gauge theories cannot be defined on the lattice. This is called the no-go theorem. It implies that if {Gamma}/sub/A is defined on a lattice then its infrared limit, which should correspond to the quantum description of the classical action for the slowly varying fields on lattice scale, is inevitably a vector like theory. In particular, if not circumvented, the no-go theorem implies that there is no lattice formulation of the Standard Weinberg-Salam theory or SU(5) GUT, even though the fermions belong to anomaly-free representations of the gauge group. This talk aims to explain one possible attempt at bypassing the no-go theorem. 20 refs.

Lattice fermions

International Nuclear Information System (INIS)

Randjbar-Daemi, S.

1995-12-01

The so-called doubling problem in the lattice description of fermions led to a proof that under certain circumstances chiral gauge theories cannot be defined on the lattice. This is called the no-go theorem. It implies that if Γ/sub/A is defined on a lattice then its infrared limit, which should correspond to the quantum description of the classical action for the slowly varying fields on lattice scale, is inevitably a vector like theory. In particular, if not circumvented, the no-go theorem implies that there is no lattice formulation of the Standard Weinberg-Salam theory or SU(5) GUT, even though the fermions belong to anomaly-free representations of the gauge group. This talk aims to explain one possible attempt at bypassing the no-go theorem. 20 refs

Nonclassicality by Local Gaussian Unitary Operations for Gaussian States

Directory of Open Access Journals (Sweden)

Yangyang Wang

2018-04-01

Full Text Available A measure of nonclassicality N in terms of local Gaussian unitary operations for bipartite Gaussian states is introduced. N is a faithful quantum correlation measure for Gaussian states as product states have no such correlation and every non product Gaussian state contains it. For any bipartite Gaussian state ρ A B , we always have 0 ≤ N ( ρ A B < 1 , where the upper bound 1 is sharp. An explicit formula of N for ( 1 + 1 -mode Gaussian states and an estimate of N for ( n + m -mode Gaussian states are presented. A criterion of entanglement is established in terms of this correlation. The quantum correlation N is also compared with entanglement, Gaussian discord and Gaussian geometric discord.

Fermionic spectral functions in backreacting p-wave superconductors at finite temperature

Energy Technology Data Exchange (ETDEWEB)

Giordano, G.L.; Grandi, N.E.; Lugo, A.R. [Instituto de Física de La Plata - CONICET & Departamento de Física - UNLP,C.C. 67, 1900 La Plata (Argentina)

2017-04-14

We investigate the spectral function of fermions in a p-wave superconducting state, at finite both temperature and gravitational coupling, using the AdS/CFT correspondence and extending previous research. We found that, for any coupling below a critical value, the system behaves as its zero temperature limit. By increasing the coupling, the “peak-dip-hump” structure that characterizes the spectral function at fixed momenta disappears. In the region where the normal/superconductor phase transition is first order, the presence of a non-zero order parameter is reflected in the absence of rotational symmetry in the fermionic spectral function at the critical temperature.

Interacting fermions on a random lattice

International Nuclear Information System (INIS)

Perantonis, S.J.; Wheater, J.F.

1988-01-01

We extend previous work on the properties of the Dirac lagrangian on two-dimensional random lattices to the case where interaction terms are included. Although for free fermions the chiral symmetry of the doubles is spontaneously broken by their interaction with the lattice and tehy decouple from long-distance physics, our results in this paper show that all is undone by quantum corrections in an interacting field theory and taht the end result is very similar to what is found with Wilson fermions. Two field-theoretical models with interacting fermions are studied by perturbation expansion in the field theory coupling constant. These are a model with one fermion and one boson species interacting via a scalar Yukawa coupling and the massive Thirring model. It is shown that on the random lattice ultraviolet finite diagrams and finite parts of ultraviolet divergent diagrams have the correct continuum limit. Ultraviolet divergent parts can be removed by the same renormalisation procedure as in the continuum, but do not exhibit the same dependence on the lagrangian mass. In the case of the massive Thirring model this causes a fermion mass correction of order the cut-off scale, which breaks the chiral symmetry of the remaining light fermion; there is consequently a fine-tuning problem. In the context of the same model we discuss the effect of the Goldstone boson associated with the spontaneous breakdown of the chiral symmetry of the doubles on two-dimensional models with vector couplings. (orig.)

Lattice quantum chromodynamics with approximately chiral fermions

International Nuclear Information System (INIS)

Hierl, Dieter

2008-05-01

In this work we present Lattice QCD results obtained by approximately chiral fermions. We use the CI fermions in the quenched approximation to investigate the excited baryon spectrum and to search for the Θ + pentaquark on the lattice. Furthermore we developed an algorithm for dynamical simulations using the FP action. Using FP fermions we calculate some LECs of chiral perturbation theory applying the epsilon expansion. (orig.)

Lattice quantum chromodynamics with approximately chiral fermions

Energy Technology Data Exchange (ETDEWEB)

Hierl, Dieter

2008-05-15

In this work we present Lattice QCD results obtained by approximately chiral fermions. We use the CI fermions in the quenched approximation to investigate the excited baryon spectrum and to search for the {theta}{sup +} pentaquark on the lattice. Furthermore we developed an algorithm for dynamical simulations using the FP action. Using FP fermions we calculate some LECs of chiral perturbation theory applying the epsilon expansion. (orig.)

Disordered Dirac fermions: the marriage of three different approaches

Energy Technology Data Exchange (ETDEWEB)

Bhaseen, Miraculous J. E-mail: bhaseen@thphys.ox.ac.uk; Caux, J.-S. E-mail: caux@thphys.ox.ac.uk; Kogan, Ian I. E-mail: kogan@thphys.ox.ac.uk; Tsvelik, Alexei M. E-mail: tsvelik@thphys.ox.ac.uk

2001-12-17

We compare the critical multipoint correlation functions for two-dimensional (massless) Dirac fermions in the presence of a random su(N) (non-Abelian) gauge potential, obtained by three different methods. We critically reexamine previous results obtained using the replica approach and in the limit of infinite disorder strength and compare them to new results (presented here) obtained using the supersymmetric approach to the N=2 case. We demonstrate that this menage a trois of different approaches leads to identical results. Remarkable relations between apparently different conformal field theories (CFTs) are thereby obtained. We further establish a connection between the random Dirac fermion problem and the c=-2 theory of dense polymers. The presence of the c=-2 theory may be seen in all three different treatments of the disorder.

Disordered Dirac fermions: the marriage of three different approaches

International Nuclear Information System (INIS)

Bhaseen, Miraculous J.; Caux, J.-S.; Kogan, Ian I.; Tsvelik, Alexei M.

2001-01-01

We compare the critical multipoint correlation functions for two-dimensional (massless) Dirac fermions in the presence of a random su(N) (non-Abelian) gauge potential, obtained by three different methods. We critically reexamine previous results obtained using the replica approach and in the limit of infinite disorder strength and compare them to new results (presented here) obtained using the supersymmetric approach to the N=2 case. We demonstrate that this menage a trois of different approaches leads to identical results. Remarkable relations between apparently different conformal field theories (CFTs) are thereby obtained. We further establish a connection between the random Dirac fermion problem and the c=-2 theory of dense polymers. The presence of the c=-2 theory may be seen in all three different treatments of the disorder

Grassmann phase space theory for fermions

Energy Technology Data Exchange (ETDEWEB)

Dalton, Bryan J. [Centre for Quantum and Optical Science, Swinburne University of Technology, Melbourne, Victoria, 3122 (Australia); Jeffers, John [Department of Physics, University of Strathclyde, Glasgow, G4 ONG (United Kingdom); Barnett, Stephen M. [School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)

2017-06-15

A phase space theory for fermions has been developed using Grassmann phase space variables which can be used in numerical calculations for cold Fermi gases and for large fermion numbers. Numerical calculations are feasible because Grassmann stochastic variables at later times are related linearly to such variables at earlier times via c-number stochastic quantities. A Grassmann field version has been developed making large fermion number applications possible. Applications are shown for few mode and field theory cases. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Causal fermion systems as a candidate for a unified physical theory

International Nuclear Information System (INIS)

Finster, Felix; Kleiner, Johannes

2015-01-01

The theory of causal fermion systems is an approach to describe fundamental physics. Giving quantum mechanics, general relativity and quantum field theory as limiting cases, it is a candidate for a unified physical theory. We here give a non-technical introduction. (paper)

Unitary 4-point correlators from classical geometries

Energy Technology Data Exchange (ETDEWEB)

Bombini, Alessandro; Galliani, Andrea; Giusto, Stefano [Universita di Padova, Dipartimento di Fisica ed Astronomia ' ' Galileo Galilei' ' , Padua (Italy); I.N.F.N. Sezione di Padova, Padua (Italy); Moscato, Emanuele; Russo, Rodolfo [Queen Mary University of London, Centre for Research in String Theory, School of Physics and Astronomy, London (United Kingdom)

2018-01-15

We compute correlators of two heavy and two light operators in the strong coupling and large c limit of the D1D5 CFT which is dual to weakly coupled AdS{sub 3} gravity. The light operators have dimension two and are scalar descendants of the chiral primaries considered in arXiv:1705.09250, while the heavy operators belong to an ensemble of Ramond-Ramond ground states. We derive a general expression for these correlators when the heavy states in the ensemble are close to the maximally spinning ground state. For a particular family of heavy states we also provide a result valid for any value of the spin. In all cases we find that the correlators depend non-trivially on the CFT moduli and are not determined by the symmetries of the theory; however, they have the properties expected for correlators among pure states in a unitary theory, in particular they do not decay at large Lorentzian times. (orig.)

Goldstone fermions in supersymmetric theories at finite temperature

International Nuclear Information System (INIS)

Aoyama, H.; Boyanovsky, D.

1984-01-01

The behavior of supersymmetric theories at finite temperature is examined. It is shown that supersymmetry is broken for any T> or =0 because of the different statistics obeyed by bosons and fermions. This breaking is always associated with a Goldstone mode(s). This phenomenon is shown to take place even in a free massive theory, where the Goldstone modes are created by composite fermion-boson bilinear operators. In the interacting theory with chiral symmetry, the same bilinear operators create the chiral doublet of Goldstone fermions, which is shown to saturate the Ward-Takahashi identities up to one loop. Because of this spontaneous supersymmetry breaking, the fermions and the bosons acquire different effective masses. In theories without chiral symmetry, at the tree level the fermion-boson bilinear operators create Goldstone modes, but at higher orders these modes become massive and the elementary fermion becomes the Goldstone field because of the mixing with these bilinear operators

Black hole thermodynamics based on unitary evolutions

International Nuclear Information System (INIS)

Feng, Yu-Lei; Chen, Yi-Xin

2015-01-01

In this paper, we try to construct black hole thermodynamics based on the fact that the formation and evaporation of a black hole can be described by quantum unitary evolutions. First, we show that the Bekenstein–Hawking entropy S BH may not be a Boltzmann or thermal entropy. To confirm this statement, we show that the original black hole's ‘first law’ may not simply be treated as the first law of thermodynamics formally, due to some missing metric perturbations caused by matter. Then, by including those (quantum) metric perturbations, we show that the black hole formation and evaporation can be described effectively in a unitary manner, through a quantum channel between the exterior and interior of the event horizon. In this way, the paradoxes of information loss and firewall can be resolved effectively. Finally, we show that black hole thermodynamics can be constructed in an ordinary way, by constructing statistical mechanics. (paper)

Matrix elements and few-body calculations within the unitary correlation operator method

International Nuclear Information System (INIS)

Roth, R.; Hergert, H.; Papakonstantinou, P.

2005-01-01

We employ the unitary correlation operator method (UCOM) to construct correlated, low-momentum matrix elements of realistic nucleon-nucleon interactions. The dominant short-range central and tensor correlations induced by the interaction are included explicitly by an unitary transformation. Using correlated momentum-space matrix elements of the Argonne V18 potential, we show that the unitary transformation eliminates the strong off-diagonal contributions caused by the short-range repulsion and the tensor interaction and leaves a correlated interaction dominated by low-momentum contributions. We use correlated harmonic oscillator matrix elements as input for no-core shell model calculations for few-nucleon systems. Compared to the bare interaction, the convergence properties are dramatically improved. The bulk of the binding energy can already be obtained in very small model spaces or even with a single Slater determinant. Residual long-range correlations, not treated explicitly by the unitary transformation, can easily be described in model spaces of moderate size allowing for fast convergence. By varying the range of the tensor correlator we are able to map out the Tjon line and can in turn constrain the optimal correlator ranges. (orig.)

Matrix elements and few-body calculations within the unitary correlation operator method

International Nuclear Information System (INIS)

Roth, R.; Hergert, H.; Papakonstantinou, P.; Neff, T.; Feldmeier, H.

2005-01-01

We employ the unitary correlation operator method (UCOM) to construct correlated, low-momentum matrix elements of realistic nucleon-nucleon interactions. The dominant short-range central and tensor correlations induced by the interaction are included explicitly by an unitary transformation. Using correlated momentum-space matrix elements of the Argonne V18 potential, we show that the unitary transformation eliminates the strong off-diagonal contributions caused by the short-range repulsion and the tensor interaction and leaves a correlated interaction dominated by low-momentum contributions. We use correlated harmonic oscillator matrix elements as input for no-core shell model calculations for few-nucleon systems. Compared to the bare interaction, the convergence properties are dramatically improved. The bulk of the binding energy can already be obtained in very small model spaces or even with a single Slater determinant. Residual long-range correlations, not treated explicitly by the unitary transformation, can easily be described in model spaces of moderate size allowing for fast convergence. By varying the range of the tensor correlator we are able to map out the Tjon line and can in turn constrain the optimal correlator ranges

Fermions

Directory of Open Access Journals (Sweden)

Boyle Peter

2018-01-01

Full Text Available We present results for the QED and strong isospin breaking corrections to the hadronic vacuum polarization using Nf = 2 + 1 Domain Wall fermions. QED is included in an electro-quenched setup using two different methods, a stochastic and a perturbative approach. Results and statistical errors from both methods are directly compared with each other.

Squeezed fermions and back-to-back correlations

International Nuclear Information System (INIS)

Panda, P.K.; Krein, G.; Padula, S.S.; Csoergoe, T.; Hama, Y.

2001-01-01

Back-to-back correlations of asymptotic fermion pairs appear if in-medium interactions lead to mass modifications of fermion states in a thermalized medium. The back-to-back correlations of protons and anti-protons will be experimentally observable in ultrarelativistic heavy ion collisions. The strength of back-to-back correlations of fermions can be unlimitedly large, diverging as the momentum of the pair increases and the net baryon density decreases. (author)

Squeezed fermions and back-to-back correlations

Energy Technology Data Exchange (ETDEWEB)

Panda, P.K.; Krein, G.; Padula, S.S. [Instituto de Fisica Teorica (IFT), Sao Paulo, SP (Brazil); Csoergoe, T. [Hungarian Academy of Sciences, Budapest (Hungary). Research Institute for Particle and Nuclear Physics (RMKI, KFKI); Hama, Y. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica

2001-07-01

Back-to-back correlations of asymptotic fermion pairs appear if in-medium interactions lead to mass modifications of fermion states in a thermalized medium. The back-to-back correlations of protons and anti-protons will be experimentally observable in ultrarelativistic heavy ion collisions. The strength of back-to-back correlations of fermions can be unlimitedly large, diverging as the momentum of the pair increases and the net baryon density decreases. (author)

Quasi-relativistic fermions and dynamical flavour oscillations

CERN Document Server

Alexandre, Jean; Mavromatos, Nick E.

2014-01-01

We introduce new Lorentz-symmetry violating kinematics for a four-fermion interaction model, where dynamical mass generation is allowed, irrespectively of the strength of the coupling. In addition, these kinematics lead to a quasi-relativistic dispersion relation, in the sense that it is relativistic in both the infrared and the ultraviolet, but not in an intermediate regime, characterized by the mass $M$. For two fermions, we show that a flavour-mixing mass matrix is generated dynamically, and the Lorentz symmetric limit $M\\to\\infty$ leads to two free relativistic fermions, with flavour oscillations. This model, valid for either Dirac or Majorana fermions, can describe any set of phenomenological values for the eigen masses and the mixing angle.

Role of four-fermion interaction and impurity in the states of two-dimensional semi-Dirac materials.

Science.gov (United States)

Wang, Jing

2018-03-28

We study the effects of four-fermion interaction and impurity on the low-energy states of 2D semi-Dirac materials by virtue of the unbiased renormalization group approach. The coupled flow equations that govern the energy-dependent evolutions of all correlated interaction parameters are derived after taking into account one-loop corrections from the interplay between four-fermion interaction and impurity. Whether and how four-fermion interaction and impurity influence the low-energy properties of 2D semi-Dirac materials are discreetly explored and addressed attentively. After carrying out the standard renormalization group analysis, we find that both trivial insulating and nontrivial semimetal states are qualitatively stable against all four kinds of four-fermion interactions. However, while switching on both four-fermion interaction and impurity, certain insulator-semimetal phase transitions and the distance of Dirac nodal points can be respectively induced and modified due to their strong interplay and intimate competition. Moreover, several non-Fermi liquid behaviors that deviate from the conventional Fermi liquids are exhibited at the lowest-energy limit.

Quasinormal modes of brane-localized standard model fields. II. Kerr black holes

International Nuclear Information System (INIS)

Kanti, P.; Konoplya, R. A.; Zhidenko, A.

2006-01-01

This paper presents a comprehensive study of the fundamental quasinormal modes of all standard model fields propagating on a brane embedded in a higher-dimensional rotating black-hole spacetime. The equations of motion for fields with spin s=0, 1/2 and 1 propagating in the induced-on-the-brane background are solved numerically, and the dependence of their QN spectra on the black-hole angular momentum and dimensionality of spacetime is investigated. It is found that the brane-localized field perturbations are longer-lived when the higher-dimensional black hole rotates faster, while an increase in the number of transverse-to-the-brane dimensions reduces their lifetime. Finally, the quality factor Q, that determines the best oscillator among the different field perturbations, is investigated and found to depend on properties of both the particular field studied (spin, multipole numbers) and the gravitational background (dimensionality, black-hole angular momentum parameter)

New Class of Quasinormal Modes of Neutron Stars in Scalar-Tensor Gravity

Science.gov (United States)

Mendes, Raissa F. P.; Ortiz, Néstor

2018-05-01

Detection of the characteristic spectrum of pulsating neutron stars can be a powerful tool not only to probe the nuclear equation of state but also to test modifications to general relativity. However, the shift in the oscillation spectrum induced by modified theories of gravity is often small and degenerate with our ignorance of the equation of state. In this Letter, we show that the coupling to additional degrees of freedom present in modified theories of gravity can give rise to new families of modes, with no counterpart in general relativity, which could be sufficiently well resolved in frequency space to allow for clear detection. We present a realization of this idea by performing a thorough study of radial oscillations of neutron stars in massless scalar-tensor theories of gravity. We anticipate astrophysical scenarios where the presence of this class of quasinormal modes could be probed with electromagnetic and gravitational wave measurements.

Wilson Fermions and Axion Electrodynamics in Optical Lattices

International Nuclear Information System (INIS)

Bermudez, A.; Martin-Delgado, M. A.; Mazza, L.; Rizzi, M.; Goldman, N.; Lewenstein, M.

2010-01-01

We show that ultracold Fermi gases in optical superlattices can be used as quantum simulators of relativistic lattice fermions in 3+1 dimensions. By exploiting laser-assisted tunneling, we find an analogue of the so-called naive Dirac fermions, and thus provide a realization of the fermion doubling problem. Moreover, we show how to implement Wilson fermions, and discuss how their mass can be inverted by tuning the laser intensities. In this regime, our atomic gas corresponds to a phase of matter where Maxwell electrodynamics is replaced by axion electrodynamics: a 3D topological insulator.

Quantum geometry of the Dirac fermions

International Nuclear Information System (INIS)

Korchemskij, G.P.

1989-01-01

The bosonic path integral formalism is developed for Dirac fermions interacting with a nonabelian gauge field in the D-dimensional Euclidean space-time. The representation for the effective action and correlation functions of interacting fermions as sums over all bosonic paths on the complex projective space CP 2d-1 , (2d=2 [ D 2] is derived where all the spinor structure is absorbed by the one-dimensional Wess-Zumino term. It is the Wess-Zumino term that ensures all necessary properties of Dirac fermions under quantization. i.e., quantized values of the spin, Dirac equation, Fermi statistics. 19 refs

Fermionic NNLO contributions to Bhabha scattering

International Nuclear Information System (INIS)

Actis, S.; Riemann, T.; Czakon, M.; Uniwersytet Slaski, Katowice; Gluza, J.

2007-10-01

We derive the two-loop corrections to Bhabha scattering from heavy fermions using dispersion relations. The double-box contributions are expressed by three kernel functions. Convoluting the perturbative kernels with fermionic threshold functions or with hadronic data allows to determine numerical results for small electron mass m e , combined with arbitrary values of the fermion mass m f in the loop, m 2 e 2 f , or with hadronic insertions. We present numerical results for m f =m μ , m τ ,m top at typical small- and large-angle kinematics ranging from 1 GeV to 500 GeV. (orig.)

Scaling and crossover in a fermion-boson mixture

International Nuclear Information System (INIS)

Singh, K.K.

1987-01-01

Thermodynamic behaviour of a mixture of weakly interacting fermions and bosons is investigated in (4 - ε) dimensions by the renormalization group method with a view to study scaling and crossover properties of the system in the tricritical region. Conventional tricritical scaling, first found to breakdown for a classical infinite-component model, is seen to do so more spectacularly in the case of the mixture. Whereas in the infinite-component model, conventional scaling holds in the ordered and disordered phases separately (i.e. with different tricritical exponents), no such thing is possible in either of the phases of the mixture. The breakdown of scaling in the mixture is associated with the dimensionless strength v 6 of the 6-point interaction in the effective Hamiltonian which causes the parameters of the renormalized Hamiltonian to depend on two combinations of scaling fields rather than one. The strength v 6 is a quantum mechanical parameter being proportional in 3 dimensions to (b 3 /λ T 4 K F ) where λ T , K F and b denote, respectively, the boson thermal wavelength, the Fermi momentum of the fermion component and the scattering length associated with the fermion-boson interaction. The square root of this quantity agrees with the non-universality parameter which was found to characterize tricritical amplitude ratios in 3 dimensions in an earlier work. (author). 19 refs, 8 figs

Fermions, Skyrmions and the 3-sphere

International Nuclear Information System (INIS)

Goatham, Stephen W; Krusch, Steffen

2010-01-01

This paper investigates a background charge one Skyrme field chirally coupled to light fermions on the 3-sphere. The Dirac equation for the system commutes with a generalized angular momentum or grand spin. It can be solved explicitly for a Skyrme configuration given by the hedgehog form. The energy spectrum and degeneracies are derived for all values of the grand spin. Solutions for non-zero grand spin are each characterized by a set of four polynomials. The paper also discusses the energy of the Dirac sea using zeta-function regularization.

Factorization of J-unitary matrix polynomials on the line and a Schur algorithm for generalized Nevanlinna functions

NARCIS (Netherlands)

Alpay, D.; Dijksma, A.; Langer, H.

2004-01-01

We prove that a 2 × 2 matrix polynomial which is J-unitary on the real line can be written as a product of normalized elementary J-unitary factors and a J-unitary constant. In the second part we give an algorithm for this factorization using an analog of the Schur transformation.

Fermions in Brans-Dicke cosmology

International Nuclear Information System (INIS)

Samojeden, L. L.; Devecchi, F. P.; Kremer, G. M.

2010-01-01

Using the Brans-Dicke theory of gravitation we put under investigation a hypothetical universe filled with a fermionic field (with a self-interaction potential) and a matter constituent ruled by a barotropic equation of state. It is shown that the fermionic field [in combination with the Brans-Dicke scalar field φ(t)] could be responsible for a final accelerated era, after an initial matter dominated period.

DU and UD-invariants of unitary groups

International Nuclear Information System (INIS)

Aguilera-Navarro, M.C.K.

1977-01-01

Four distint ways of obtaining the eigenvalues of unitary groups, in any irreducible representation, are presented. The invariants are defined according to two different contraction conventions. Their eigenvalue can be given in terms of two classes of special partial hooks associated with the young diagram characterizing the irreducible representation considered

Stability issues of black hole in non-local gravity

Science.gov (United States)

Myung, Yun Soo; Park, Young-Jai

2018-04-01

We discuss stability issues of Schwarzschild black hole in non-local gravity. It is shown that the stability analysis of black hole for the unitary and renormalizable non-local gravity with γ2 = - 2γ0 cannot be performed in the Lichnerowicz operator approach. On the other hand, for the unitary and non-renormalizable case with γ2 = 0, the black hole is stable against the metric perturbations. For non-unitary and renormalizable local gravity with γ2 = - 2γ0 = const (fourth-order gravity), the small black holes are unstable against the metric perturbations. This implies that what makes the problem difficult in stability analysis of black hole is the simultaneous requirement of unitarity and renormalizability around the Minkowski spacetime.

The principle of the Fermionic projector

CERN Document Server

Finster, Felix

2006-01-01

The "principle of the fermionic projector" provides a new mathematical framework for the formulation of physical theories and is a promising approach for physics beyond the standard model. This book begins with a brief review of relativity, relativistic quantum mechanics, and classical gauge theories, emphasizing the basic physical concepts and mathematical foundations. The external field problem and Klein's paradox are discussed and then resolved by introducing the fermionic projector, a global object in space-time that generalizes the notion of the Dirac sea. At the mathematical core of the book is a precise definition of the fermionic projector and the use of methods of hyperbolic differential equations for detailed analysis. The fermionic projector makes it possible to formulate a new type of variational principle in space-time. The mathematical tools are developed for the analysis of the corresponding Euler-Lagrange equations. A particular variational principle is proposed that gives rise to an effective...

Extra Z neutral bosons, families and heavy fermions

International Nuclear Information System (INIS)

Li Tiezhong

1989-08-01

The minimal Grand Unified Theories with three-family should include two extra Z neufral bosons which belong to the different broken scales. Georgi's argument on heavy Dirac fermions has been realized. These fermions should not be bizarre. The extra Z and Dirac fermions are not too heavy. The difficulty of the proton decay may be resolved

The hidden fermions in Z(2) theories

International Nuclear Information System (INIS)

Srednicki, M.

1983-01-01

Low dimensional Z(2) gauge theories have been rewritten in terms of locally coupled fermionic degrees of freedom by means of the Jordan-Wigner transformation. In this paper it is shown that higher dimensional Z(2) gauge theories are also fermionic theories in disguise. The SML solution to the 1+1 dimension Ising model is reviewed. Psi operators are represented pictorially as arrows, psi 1 points to the left, psi 2 to the right, each site of H a multiple of two operators. The 2+1 dimension Ising model is then considered. A fermion plaquette operator is introduced as the generator of a gauge symmetry for the fermionic H. Findings in 1+1 and 2+1 are then applied to 3+1 dimensional Z(2) gauge theory. A construction of this lattice is undertaken. Psi formalism replaces sigma formalism, as it permits extremely simple duality transformations to be made on any Z(2) Hamiltonian. It is shown that the fermionic formalism will lead to new ideas in Z(2) theories

On ghost fermions

International Nuclear Information System (INIS)

Grensing, G.

2002-01-01

The path integral for ghost fermions, which is heuristically made use of in the Batalin-Fradkin-Vilkovisky approach to quantization of constrained systems, is derived from first principles. The derivation turns out to be rather different from that of physical fermions since the definition of Dirac states for ghost fermions is subtle. With these results at hand, it is then shown that the nonminimal extension of the Becchi-Rouet-Stora-Tyutin operator must be chosen differently from the notorious choice made in the literature in order to avoid the boundary terms that have always plagued earlier treatments. Furthermore it is pointed out that the elimination of states with nonzero ghost number requires the introduction of a thermodynamic potential for ghosts; the reason is that Schwarz's Lefschetz formula for the partition function of the time-evolution operator is not capable, despite claims to the contrary, to get rid of nonzero ghost number states on its own. Finally, we comment on the problems of global topological nature that one faces in the attempt to obtain the solutions of the Dirac condition for physical states in a configuration space of nontrivial geometry; such complications give rise to anomalies that do not obey the Wess-Zumino consistency conditions. (orig.)

S-wave scattering of fermion revisited

International Nuclear Information System (INIS)

Rahaman, Anisur

2011-01-01

A model where a Dirac fermion is coupled to background dilaton field is considered to study s-wave scattering of fermion by a back ground dilaton black hole. It is found that an uncomfortable situation towards information loss scenario arises when one loop correction gets involved during bosonization.

FCNC Effects in a Minimal Theory of Fermion Masses

CERN Document Server

Buras, Andrzej J; Pokorski, Stefan; Ziegler, Robert

2011-01-01

As a minimal theory of fermion masses we extend the SM by heavy vectorlike fermions, with flavor-anarchical Yukawa couplings, that mix with chiral fermions such that small SM Yukawa couplings arise from small mixing angles. This model can be regarded as an effective description of the fermionic sector of a large class of existing flavor models and thus might serve as a useful reference frame for a further understanding of flavor hierarchies in the SM. Already such a minimal framework gives rise to FCNC effects through exchange of massive SM bosons whose couplings to the light fermions get modified by the mixing. We derive general formulae for these corrections and discuss the bounds on the heavy fermion masses. Particularly stringent bounds, in a few TeV range, come from the corrections to the Z couplings.

Trapped Fermions with Density Imbalance in the Bose-Einstein Condensate Limit

International Nuclear Information System (INIS)

Pieri, P.; Strinati, G.C.

2006-01-01

We analyze the effects of imbalancing the populations of two-component trapped fermions, in the Bose-Einstein condensate limit of the attractive interaction between different fermions. Starting from the gap equation with two fermionic chemical potentials, we derive a set of coupled equations that describe composite bosons and excess fermions. We include in these equations the processes leading to the correct dimer-dimer and dimer-fermion scattering lengths. The coupled equations are then solved in the Thomas-Fermi approximation to obtain the density profiles for composite bosons and excess fermions, which are relevant to the recent experiments with trapped fermionic atoms

On the trace anomaly of a Weyl fermion

Energy Technology Data Exchange (ETDEWEB)

Bastianelli, Fiorenzo; Martelli, Riccardo [Dipartimento di Fisica e Astronomia, Università di Bologna,via Irnerio 46, I-40126 Bologna (Italy); INFN - Sezione di Bologna,via Irnerio 46, I-40126 Bologna (Italy)

2016-11-29

We calculate the trace anomaly of a Weyl fermion coupled to gravity by using Fujikawa’s method supplemented by a consistent regulator. The latter is constructed out of Pauli-Villars regulating fields. The motivation for presenting such a calculation stems from recent studies that suggest that the trace anomaly of chiral fermions in four dimensions might contain an imaginary part proportional to the Pontryagin density. We find that the trace anomaly of a Weyl fermion is given by half the trace anomaly of a Dirac fermion, so that no imaginary part proportional to the Pontryagin density is seen to arise.

On the regularized fermionic projector of the vacuum

Science.gov (United States)

Finster, Felix

2008-03-01

We construct families of fermionic projectors with spherically symmetric regularization, which satisfy the condition of a distributional MP-product. The method is to analyze regularization tails with a power law or logarithmic scaling in composite expressions in the fermionic projector. The resulting regularizations break the Lorentz symmetry and give rise to a multilayer structure of the fermionic projector near the light cone. Furthermore, we construct regularizations which go beyond the distributional MP-product in that they yield additional distributional contributions supported at the origin. The remaining freedom for the regularization parameters and the consequences for the normalization of the fermionic states are discussed.

On the regularized fermionic projector of the vacuum

International Nuclear Information System (INIS)

Finster, Felix

2008-01-01

We construct families of fermionic projectors with spherically symmetric regularization, which satisfy the condition of a distributional MP-product. The method is to analyze regularization tails with a power law or logarithmic scaling in composite expressions in the fermionic projector. The resulting regularizations break the Lorentz symmetry and give rise to a multilayer structure of the fermionic projector near the light cone. Furthermore, we construct regularizations which go beyond the distributional MP-product in that they yield additional distributional contributions supported at the origin. The remaining freedom for the regularization parameters and the consequences for the normalization of the fermionic states are discussed

The effect of six-point one-particle reducible local interactions in the dual fermion approach

International Nuclear Information System (INIS)

Katanin, A A

2013-01-01

We formulate the dual fermion approach for strongly correlated electronic systems in terms of the lattice and dual effective interactions, obtained by using the covariation splitting formula. This allows us to consider the effect of six-point one-particle reducible interactions, which are usually neglected by the dual fermion approach. We show that the consideration of one-particle reducible six-point (as well as higher order) vertices is crucially important for the diagrammatic consistency of this approach. In particular, the relation between the dual and lattice self-energy, derived in the dual fermion approach, implicitly accounts for the effect of the diagrams, containing six-point and higher order local one-particle reducible vertices, and should be applied with caution, if these vertices are neglected. Apart from that, the treatment of the self-energy feedback is also modified by six-point and higher order vertices; these vertices are also important to account for some non-local corrections to the lattice self-energy, which have the same order in the local four-point vertices as the diagrams usually considered in the approach. These observations highlight an importance of six-point and higher order vertices in the dual fermion approach, and call for the development of new schemes of treatment of non-local fluctuations, which are based on one-particle irreducible quantities. (paper)

Microscopic description and excitation of unitary analog states

Energy Technology Data Exchange (ETDEWEB)

Kisslinger, L S [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA); Van Giai, N [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire

1977-12-05

A microscopic investigation in a self-consistent particle-hole model reveals approximate unitary analog states in spite of large symmetry breaking. The K-nucleus elastic scattering and (K/sup -/, ..pi../sup -/) excitation of these states are studied, showing strong surface effects.

Remarks on unitary representations of Poincare group

International Nuclear Information System (INIS)

Burzynski, A.

1979-01-01

In this paper the elementary review of methods and notions using in the theory of unitary representations of Poincare group is included. The Poincare group is a basic group for relativistic quantum mechanics. Our aim is to introduce the reader into some problems of quantum physics, which are difficult approachable for beginners. (author)

Perturbative improvement of staggered fermions using fat links

International Nuclear Information System (INIS)

Lee, Weonjong

2002-01-01

We study the possibility of improving staggered fermions using various fat links in order to reduce perturbative corrections to the gauge-invariant staggered fermion operators. We prove five theorems on SU(3) projection, triviality in renormalization, multiple SU(3) projections, uniqueness, and equivalence. As a result of these theorems, we show that, at the one-loop level, the renormalization of staggered fermion operators is identical between SU(3) projected Fat7 links and hypercubic links, as long as the action and operators are constructed by imposing the same perturbative improvement condition. In addition, we propose a new view of SU(3) projection as a tool of tadpole improvement for the staggered fermion doublers. As a conclusion, we present alternative choices of constructing fat links to improve the staggered fermion action and operators, which deserve further investigation

Nucleon electromagnetic form factors with Wilson fermions

International Nuclear Information System (INIS)

Goeckeler, M.; Haegler, P.; Horsley, R.

2007-10-01

The nucleon electromagnetic form factors continue to be of major interest for experimentalists and phenomenologists alike. They provide important insights into the structure of nuclear matter. For a range of interesting momenta they can be calculated on the lattice. The limiting factor continues to be the value of the pion mass. We present the latest results of the QCDSF collaboration using gauge configurations with two dynamical, non-perturbatively improved Wilson fermions at pion masses as low as 350 MeV. (orig.)

Nucleon electromagnetic form factors with Wilson fermions

Energy Technology Data Exchange (ETDEWEB)

Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)

2007-10-15

The nucleon electromagnetic form factors continue to be of major interest for experimentalists and phenomenologists alike. They provide important insights into the structure of nuclear matter. For a range of interesting momenta they can be calculated on the lattice. The limiting factor continues to be the value of the pion mass. We present the latest results of the QCDSF collaboration using gauge configurations with two dynamical, non-perturbatively improved Wilson fermions at pion masses as low as 350 MeV. (orig.)

Level Density In Interacting Boson-Fermion-Fermion Model (IBFFM) Of The Odd-Odd Nucleus 196Au

International Nuclear Information System (INIS)

Kabashi, Skender; Bekteshi, Sadik

2007-01-01

The level density of the odd-odd nucleus 196Au is investigated in the interacting boson-fermion-fermion model (IBFFM) which accounts for collectivity and complex interaction between quasiparticle and collective modes.The IBFFM total level density is fitted by Gaussian and its tail is also fitted by Bethe formula and constant temperature Fermi gas model

An exact fermion-pair to boson mapping

International Nuclear Information System (INIS)

Johnson, C.W.

1993-01-01

I derive in a novel fashion exact formulas for the calculation of general matrix elements, including the overlap (norm) matrix, between states constructed from fermion pairs. Mapping the fermion pairs to bosons, I show how to construct finite and exact (in the sense of preserving matrix elements) boson representations of the norm operator and one- and two-fermion operators. This may lead to a microscopic basis for the Interacting Boson Model, as well as new truncation schemes for the nuclear shell model

Collective Interference of Composite Two-Fermion Bosons

DEFF Research Database (Denmark)

Tichy, Malte; Bouvrie, Peter Alexander; Mølmer, Klaus

2012-01-01

The composite character of two-fermion bosons manifests itself in the interference of many composites as a deviation from the ideal bosonic behavior. A state of many composite bosons can be represented as a superposition of different numbers of perfect bosons and fermions, which allows us...... to provide the full Hong–Ou–Mandel-like counting statistics of interfering composites. Our theory quantitatively relates the deviation from the ideal bosonic interference pattern to the entanglement of the fermions within a single composite boson....

Zero-energy modes, charge conjugation, and fermion number

International Nuclear Information System (INIS)

Sudarshan, E.C.G.; Yajnik, U.A.

1986-01-01

States with a half-integer fermion number occur when a fermionic field coupled to a soliton possesses a zero mode. This paper spells out the circumstances under which one can retain an integer fermion number as also a charge-conjugation-invariant ground state. It is necessary to make the representation reducible but it is kept irreducible by introducing an additional operator

Quasiparticle scattering spectroscopy (QPS) of Kondo lattice heavy fermions

Science.gov (United States)

Greene, L. H.; Narasiwodeyar, S. M.; Banerjee, P.; Park, W. K.; Bauer, E. D.; Tobash, P. H.; Baumbach, R. E.; Ronning, F.; Sarrao, J. L.; Thompson, J. D.

2013-03-01

Point-contact spectroscopy (PCS) is a powerful technique to study electronic properties via measurements of non-linear current-voltage characteristic across a ballistic junction. It has been frequently adopted to investigate novel and/or unconventional superconductors by detecting the energy-dependent Andreev scattering. PCS of non-superconducting materials has been much rarely reported. From our recent studies on heavy fermions, we have frequently observed strongly bias-dependent and asymmetric conductance behaviors. Based on a Fano resonance model in a Kondo lattice, we attribute them to energy-dependent quasiparticle scattering off hybridized renormalized electronic states, dubbing it QPS. We will present our QPS results on several heavy-fermion systems and discuss QPS as a novel technique to probe the bulk spectroscopic properties of the electronic structure. For instance, it reveals that the hybridization gap in URu2Si2 opens well above the hidden order transition. The work at UIUC is supported by the U.S. DOE under Award No. DE-FG02-07ER46453 and the NSF DMR 12-06766, and the work at LANL is carried out under the auspices of the U.S. DOE, Office of Science.

Fermion families and vacuum in the two measures theory

International Nuclear Information System (INIS)

Guendelman, E.; Kaganovich, A.

2005-01-01

We present an alternative gravity and matter fields theory where the consistency condition of equations of motion yields strong correlation between states of 'primordial' fermion fields and local value of the scalar fields (dilaton and Higgs) energy density. The same 'primordial' fermion field at different densities can be either in states of regular fermionic matter or in states presumably corresponding to the dark fermionic matter. In regime of the fermion densities typical for normal particle physics, each of the primordial fermions splits into three generations identified with regular fermions. When restricting ourselves to the first two fermion generations, the theory reproduces general relativity and regular particle theory. As fermion energy density is comparable with vacuum energy density, the theory allows new type of states. Such Cosmo-Low Energy Physics (CLEP) state is studied in the framework of the model where FRW universe filled with homogeneous scalar field and uniformly distributed nonrelativistic neutrinos. Neutrinos in CLEP state are drawn into cosmological expansion by means of dynamically changing their own parameters. Some of the features of the CLEP state in the late time universe: neutrino mass increases as α 3/2 (α = α(t) is the scale factor); its energy density scales as a sort of dark energy and approaches constant as α→∞; this cold dark matter possesses negative pressure and its equation of state approaches that of the cosmological constant as α→∞; the total energy density of such universe is less than it would be in the universe free of fermionic matter at all. The latter means that nonrelativistic neutrinos are able to produce expanding bubbles of the CLEP state playing the role of a true 'cosmological vacuum' surrounded by a 'regular' vacuum. (authors)

Born-Kothari Condensation for Fermions

Directory of Open Access Journals (Sweden)

Arnab Ghosh

2017-09-01

Full Text Available In the spirit of Bose–Einstein condensation, we present a detailed account of the statistical description of the condensation phenomena for a Fermi–Dirac gas following the works of Born and Kothari. For bosons, while the condensed phase below a certain critical temperature, permits macroscopic occupation at the lowest energy single particle state, for fermions, due to Pauli exclusion principle, the condensed phase occurs only in the form of a single occupancy dense modes at the highest energy state. In spite of these rudimentary differences, our recent findings [Ghosh and Ray, 2017] identify the foregoing phenomenon as condensation-like coherence among fermions in an analogous way to Bose–Einstein condensate which is collectively described by a coherent matter wave. To reach the above conclusion, we employ the close relationship between the statistical methods of bosonic and fermionic fields pioneered by Cahill and Glauber. In addition to our previous results, we described in this mini-review that the highest momentum (energy for individual fermions, prerequisite for the condensation process, can be specified in terms of the natural length and energy scales of the problem. The existence of such condensed phases, which are of obvious significance in the context of elementary particles, have also been scrutinized.

Itinerant quantum multicriticality of two-dimensional Dirac fermions

Science.gov (United States)

Roy, Bitan; Goswami, Pallab; Juričić, Vladimir

2018-05-01

We analyze emergent quantum multicriticality for strongly interacting, massless Dirac fermions in two spatial dimensions (d =2 ) within the framework of Gross-Neveu-Yukawa models, by considering the competing order parameters that give rise to fully gapped (insulating or superconducting) ground states. We focus only on those competing orders which can be rotated into each other by generators of an exact or emergent chiral symmetry of massless Dirac fermions, and break O(S1) and O(S2) symmetries in the ordered phase. Performing a renormalization-group analysis by using the ɛ =(3 -d ) expansion scheme, we show that all the coupling constants in the critical hyperplane flow toward a new attractive fixed point, supporting an enlarged O(S1+S2) chiral symmetry. Such a fixed point acts as an exotic quantum multicritical point (MCP), governing the continuous semimetal-insulator as well as insulator-insulator (for example, antiferromagnet to valence bond solid) quantum phase transitions. In comparison with the lower symmetric semimetal-insulator quantum critical points, possessing either O(S1) or O(S2) chiral symmetry, the MCP displays enhanced correlation length exponents, and anomalous scaling dimensions for both fermionic and bosonic fields. We discuss the scaling properties of the ratio of bosonic and fermionic masses, and the increased dc resistivity at the MCP. By computing the scaling dimensions of different local fermion bilinears in the particle-hole channel, we establish that most of the four fermion operators or generalized density-density correlation functions display faster power-law decays at the MCP compared to the free fermion and lower symmetric itinerant quantum critical points. Possible generalization of this scenario to higher-dimensional Dirac fermions is also outlined.

Chiral composite fermions without U(1)'s

International Nuclear Information System (INIS)

Nelson, A.E.

1986-01-01

Some models are discussed which seem likely to produce composite fermions with masses protected only by nonabelian global symmetries. A subgroup of the original global symmetries can be weakly gauged to produce small masses for the fermions. A new feature of these models is that the original global symmetries contain no abelian factors and below the confinement scale there are neither exactly massless fermions nor Goldstone bosons. A candidate is given for a potentially realistic model with up to six families of quarks and leptons. (orig.)

Fermion frontiers in vector lattice gauge theories: Proceedings. Volume 8

International Nuclear Information System (INIS)

1998-01-01

The inclusion of fermions into simulations of lattice gauge theories is very difficult both theoretically and numerically. With the presence of Teraflops-scale computers for lattice gauge theory, the authors wanted a forum to discuss new approaches to lattice fermions. The workshop concentrated on approaches which are ripe for study on such large machines. Although lattice chiral fermions are vitally important to understand, there is not technique at hand which is viable on these Teraflops-scale machines for real-world problems. The discussion was therefore focused on recent developments and future prospects for QCD-like theories. For the well-known fermion formulations, the Aoki phase in Wilson fermions, novelties of U A (1) symmetry and the η' for staggered fermions and new approaches for simulating the determinant for Wilson fermions were discussed. The newer domain-wall fermion formulation was reviewed, with numerical results given by many speakers. The fermion proposal of Friedberg, Lee and Pang was introduced. They also were able to compare and contrast the dependence of QCD and QCD-like SUSY theories on the number of quark flavors. These proceedings consist of several transparencies and a summary page from each speaker. This should serve to outline the major points made in each talk

Elegant Coercion and Iran: Beyond the Unitary Actor Model

National Research Council Canada - National Science Library

Moss, J. C

2005-01-01

.... At its core, then, coercion is about state decision-making. Most theories of coercion describe states as if they were unitary actors whose decision-making results from purely rational cost-benefit calculations...

Coherent state path integral and super-symmetry for condensates composed of bosonic and fermionic atoms

International Nuclear Information System (INIS)

Mieck, B.

2007-01-01

A super-symmetric coherent state path integral on the Keldysh time contour is considered for bosonic and fermionic atoms which interact among each other with a common short-ranged two-body potential. We investigate the symmetries of Bose-Einstein condensation for the equivalent bosonic and fermionic constituents with the same interaction potential so that a super-symmetry results between the bosonic and fermionic components of super-fields. Apart from the super-unitary invariance U(L vertical stroke S) of the density terms, we specialize on the examination of super-symmetries for pair condensate terms. Effective equations are derived for anomalous terms which are related to the molecular- and BCS- condensate pairs. A Hubbard-Stratonovich transformation from 'Nambu'-doubled super-fields leads to a generating function with super-matrices for the self-energy whose manifold is given by the orthosympletic super-group Osp(S,S vertical stroke 2L). A nonlinear sigma model follows from the spontaneous breaking of the ortho-symplectic super-group Osp(S,S vertical stroke 2L) to the coset decomposition Osp(S,S vertical stroke 2L) backslash U(L vertical stroke S) x U(L vertical stroke S). The invariant subgroup U(L vertical stroke S) for the vacuum or background fields is represented by the density terms in the self-energy whereas the super-matrices on the coset space Osp(S,S vertical stroke 2L) backslash U(L vertical stroke S) describe the anomalous molecular and BCS-pair condensate terms. A change of integration measure is performed for the coset decomposition Osp(S,S vertical stroke 2L) backslash U(L vertical stroke S) x U(L vertical stroke S), including a separation of density and anomalous parts of the self-energy with a gradient expansion for the Goldstone modes. The independent anomalous fields in the actions can be transformed by the inverse square root G Osp backslash U -1/2 of the metric tensor of Osp(S,S vertical stroke 2L) backslash U(L vertical stroke S) so that

Coherent state path integral and super-symmetry for condensates composed of bosonic and fermionic atoms

Energy Technology Data Exchange (ETDEWEB)

Mieck, B. [Department of Physics in Duisburg, University Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg (Germany)

2007-09-15

A super-symmetric coherent state path integral on the Keldysh time contour is considered for bosonic and fermionic atoms which interact among each other with a common short-ranged two-body potential. We investigate the symmetries of Bose-Einstein condensation for the equivalent bosonic and fermionic constituents with the same interaction potential so that a super-symmetry results between the bosonic and fermionic components of super-fields. Apart from the super-unitary invariance U(L vertical stroke S) of the density terms, we specialize on the examination of super-symmetries for pair condensate terms. Effective equations are derived for anomalous terms which are related to the molecular- and BCS- condensate pairs. A Hubbard-Stratonovich transformation from 'Nambu'-doubled super-fields leads to a generating function with super-matrices for the self-energy whose manifold is given by the orthosympletic super-group Osp(S,S vertical stroke 2L). A nonlinear sigma model follows from the spontaneous breaking of the ortho-symplectic super-group Osp(S,S vertical stroke 2L) to the coset decomposition Osp(S,S vertical stroke 2L) backslash U(L vertical stroke S) x U(L vertical stroke S). The invariant subgroup U(L vertical stroke S) for the vacuum or background fields is represented by the density terms in the self-energy whereas the super-matrices on the coset space Osp(S,S vertical stroke 2L) backslash U(L vertical stroke S) describe the anomalous molecular and BCS-pair condensate terms. A change of integration measure is performed for the coset decomposition Osp(S,S vertical stroke 2L) backslash U(L vertical stroke S) x U(L vertical stroke S), including a separation of density and anomalous parts of the self-energy with a gradient expansion for the Goldstone modes. The independent anomalous fields in the actions can be transformed by the inverse square root G{sub Osp} {sub backslash} {sub U}{sup -1/2} of the metric tensor of Osp(S,S vertical stroke 2L) backslash U

Fermion structures of state vectors of the Schwinger model with multi-fermions

International Nuclear Information System (INIS)

Nakawaki, Yuji

1983-01-01

Coulomb-gauge Schwinger model with multi-fermions is formulated consistently in a box [-L, L] by introducing true dynamical degrees of freedom of electromagnetic fields, namely zero-mode part A 1 sup((0)) of A 1 and its canonical conjugate momentum π 1 sup((0)). State vectors are constructed of free massless fermion operators and zero-mode operators A 1 sup((0)) and π 1 sup((0)) and it is clarified how and why multifermion condensations become degenerate ground states and chiral invariance is spontaneously broken. It is also examined that physical space of covariant gauge Schwinger model is isomorphic to that of Coulomb-gauge Schwinger model. (author)

Unconventional superconductivity in heavy-fermion compounds

Energy Technology Data Exchange (ETDEWEB)

White, B.D. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Center for Advanced Nanoscience, University of California, San Diego, La Jolla, CA 92093 (United States); Thompson, J.D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Maple, M.B., E-mail: mbmaple@ucsd.edu [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Center for Advanced Nanoscience, University of California, San Diego, La Jolla, CA 92093 (United States)

2015-07-15

Highlights: • Quasiparticles in heavy-fermion compounds are much heavier than free electrons. • Superconductivity involves pairing of these massive quasiparticles. • Quasiparticle pairing mediated by magnetic or quadrupolar fluctuations. • We review the properties of superconductivity in heavy-fermion compounds. - Abstract: Over the past 35 years, research on unconventional superconductivity in heavy-fermion systems has evolved from the surprising observations of unprecedented superconducting properties in compounds that convention dictated should not superconduct at all to performing explorations of rich phase spaces in which the delicate interplay between competing ground states appears to support emergent superconducting states. In this article, we review the current understanding of superconductivity in heavy-fermion compounds and identify a set of characteristics that is common to their unconventional superconducting states. These core properties are compared with those of other classes of unconventional superconductors such as the cuprates and iron-based superconductors. We conclude by speculating on the prospects for future research in this field and how new advances might contribute towards resolving the long-standing mystery of how unconventional superconductivity works.

Treating experimental data of inverse kinetic method by unitary linear regression analysis

International Nuclear Information System (INIS)

Zhao Yusen; Chen Xiaoliang

2009-01-01

The theory of treating experimental data of inverse kinetic method by unitary linear regression analysis was described. Not only the reactivity, but also the effective neutron source intensity could be calculated by this method. Computer code was compiled base on the inverse kinetic method and unitary linear regression analysis. The data of zero power facility BFS-1 in Russia were processed and the results were compared. The results show that the reactivity and the effective neutron source intensity can be obtained correctly by treating experimental data of inverse kinetic method using unitary linear regression analysis and the precision of reactivity measurement is improved. The central element efficiency can be calculated by using the reactivity. The result also shows that the effect to reactivity measurement caused by external neutron source should be considered when the reactor power is low and the intensity of external neutron source is strong. (authors)

Fermionic bound states in distinct kinklike backgrounds

Energy Technology Data Exchange (ETDEWEB)

Bazeia, D. [Universidade Federal da Paraiba, Departamento de Fisica, Joao Pessoa, Paraiba (Brazil); Mohammadi, A. [Universidade Federal de Campina Grande, Departamento de Fisica, Caixa Postal 10071, Campina Grande, Paraiba (Brazil)

2017-04-15

This work deals with fermions in the background of distinct localized structures in the two-dimensional spacetime. Although the structures have a similar topological character, which is responsible for the appearance of fractionally charged excitations, we want to investigate how the geometric deformations that appear in the localized structures contribute to the change in the physical properties of the fermionic bound states. We investigate the two-kink and compact kinklike backgrounds, and we consider two distinct boson-fermion interactions, one motivated by supersymmetry and the other described by the standard Yukawa coupling. (orig.)

Baby Skyrme model and fermionic zero modes

Science.gov (United States)

Queiruga, J. M.

2016-09-01

In this work we investigate some features of the fermionic sector of the supersymmetric version of the baby Skyrme model. We find that, in the background of Bogomol'nyi-Prasad-Sommerfield compact baby Skyrmions, fermionic zero modes are confined to the defect core. Further, we show that, while three Supersymmetry (SUSY) generators are broken in the defect core, SUSY is completely restored outside. We study also the effect of a D-term deformation of the model. Such a deformation allows for the existence of fermionic zero modes and broken SUSY outside the compact defect.

Instantons and Massless Fermions in Two Dimensions

Science.gov (United States)

Callan, C. G. Jr.; Dashen, R.; Gross, D. J.

1977-05-01

The role of instantons in the breakdown of chiral U(N) symmetry is studied in a two dimensional model. Chiral U(1) is always destroyed by the axial vector anomaly. For N = 2 chiral SU(N) is also spontaneously broken yielding massive fermions and three (decoupled) Goldstone bosons. For N greater than or equal to 3 the fermions remain massless. Realistic four dimensional theories are believed to behave in a similar way but the critical N above which the fermions cease to be massive is not known in four dimensions.

A remark on the unitary group of a tensor product of n finite ...

Indian Academy of Sciences (India)

By using the method of quantum circuits in the theory of quantum computing as outlined in Nielsen and Chuang [2] and using a key lemma of Jaikumar [1] we show that every unitary operator on the tensor product H = H 1 ⊗ H 2 ⊗ … ⊗ H n can be expressed as a composition of a finite number of unitary operators living on ...

Massive chiral fermions: a natural account of chiral phenomenology in the framework of Dirac's fermion theory

International Nuclear Information System (INIS)

Ziino, G.

1989-01-01

We assume a strictly invariant definition of the Dirac parity operator under fermion ↔ antifermion exchange. We see that the opposite-intrinsic-parity condition then requires two opposite-mass Dirac equations for the fermion and the antifermion. This leads us to introduce an asymptotically left-handed (fermion) and right-handed (antifermion) chiral field, as just an alternative basis in the internal space spanned by the new pair of charge-conjugate Dirac fields. Hence a dual intrinsic model of a spin - 1/2 massive fermion is drawn: it predicts the coexistence of two anticommuting general varieties of conserved charges, namely a scalar variety, responsible for parity-invariant phenomenology, plus a pseudoscalar one, responsible for chiral phenomenology. In this light, CP-symmetry is seen to be nothing but P-symmetry; and a spontaneous CP-violation mechanism is also derived, that should work in any single process occurring via both scalar-and pseudoscalar-charge interactions. We show, at last, that our scheme automatically yields Weyl's one for a merely left-handed neutrino and a merely right-handed antineutrino, further assigning them the special meaning of pure pseudoscalar-charge objects. Some general consequences as regards magnetic monopoles are briefly discussed too

Running coupling from gluon and ghost propagators in the Landau gauge: Yang-Mills theories with adjoint fermions

Science.gov (United States)

Bergner, Georg; Piemonte, Stefano

2018-04-01

Non-Abelian gauge theories with fermions transforming in the adjoint representation of the gauge group (AdjQCD) are a fundamental ingredient of many models that describe the physics beyond the Standard Model. Two relevant examples are N =1 supersymmetric Yang-Mills (SYM) theory and minimal walking technicolor, which are gauge theories coupled to one adjoint Majorana and two adjoint Dirac fermions, respectively. While confinement is a property of N =1 SYM, minimal walking technicolor is expected to be infrared conformal. We study the propagators of ghost and gluon fields in the Landau gauge to compute the running coupling in the MiniMom scheme. We analyze several different ensembles of lattice Monte Carlo simulations for the SU(2) adjoint QCD with Nf=1 /2 ,1 ,3 /2 , and 2 Dirac fermions. We show how the running of the coupling changes as the number of interacting fermions is increased towards the conformal window.

Calculation of CWKB envelope in boson and fermion productions

International Nuclear Information System (INIS)

Biswas, S.; Chowdhury, I.

2007-01-01

We present the calculation of envelope of boson and of both low-and high-mass fermion production at the end of inflation when the coherently oscillating inflations decay into bosons and fermions. We consider three different models of inflation and use CWKB technique to calculate the envelope to understand the structure of resonance band formation. We observe that though low-mass fermion production is not effective in preheating because of Pauli blocking, it is quite probable for high-mass fermion to take part in pre heating. (author)

Spin-excited oscillations in two-component fermion condensates

International Nuclear Information System (INIS)

Maruyama, Tomoyuki; Bertsch, George F.

2006-01-01

We investigate collective spin excitations in two-component fermion condensates with special consideration of unequal populations of the two components. The frequencies of monopole and dipole modes are calculated using Thomas-Fermi theory and the scaling approximation. As the fermion-fermion coupling is varied, the system shows various phases of the spin configuration. We demonstrate that spin oscillations have more sensitivity to the spin phase structures than the density oscillations

Iterative methods for overlap and twisted mass fermions

International Nuclear Information System (INIS)

Chiarappa, T.; Jansen, K.; Shindler, A.; Wetzorke, I.; Scorzato, L.; Urbach, C.; Wenger, U.

2006-09-01

We present a comparison of a number of iterative solvers of linear systems of equations for obtaining the fermion propagator in lattice QCD. In particular, we consider chirally invariant overlap and chirally improved Wilson (maximally) twisted mass fermions. The comparison of both formulations of lattice QCD is performed at four fixed values of the pion mass between 230 MeV and 720 MeV. For overlap fermions we address adaptive precision and low mode preconditioning while for twisted mass fermions we discuss even/odd preconditioning. Taking the best available algorithms in each case we find that calculations with the overlap operator are by a factor of 30-120 more expensive than with the twisted mass operator. (orig.)

Iterative methods for overlap and twisted mass fermions

Energy Technology Data Exchange (ETDEWEB)

Chiarappa, T. [Univ. di Milano Bicocca (Italy); Jansen, K.; Shindler, A.; Wetzorke, I. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Nagai, K.I. [Wuppertal Univ. (Gesamthochschule) (Germany). Fachbereich Physik; Papinutto, M. [INFN Sezione di Roma Tre, Rome (Italy); Scorzato, L. [European Centre for Theoretical Studies in Nuclear Physics and Related Areas (ECT), Villazzano (Italy); Urbach, C. [Liverpool Univ. (United Kingdom). Dept. of Mathematical Sciences; Wenger, U. [ETH Zuerich (Switzerland). Inst. fuer Theoretische Physik

2006-09-15

We present a comparison of a number of iterative solvers of linear systems of equations for obtaining the fermion propagator in lattice QCD. In particular, we consider chirally invariant overlap and chirally improved Wilson (maximally) twisted mass fermions. The comparison of both formulations of lattice QCD is performed at four fixed values of the pion mass between 230 MeV and 720 MeV. For overlap fermions we address adaptive precision and low mode preconditioning while for twisted mass fermions we discuss even/odd preconditioning. Taking the best available algorithms in each case we find that calculations with the overlap operator are by a factor of 30-120 more expensive than with the twisted mass operator. (orig.)

Quantum tunneling and quasinormal modes in the spacetime of the Alcubierre warp drive

Science.gov (United States)

Jusufi, Kimet; Sakallı, İzzet; Övgün, Ali

2018-01-01

In a seminal paper, Alcubierre showed that Einstein's theory of general relativity appears to allow a super-luminal motion. In the present study, we use a recent eternal-warp-drive solution found by Alcubierre to study the effect of Hawking radiation upon an observer located within the warp drive in the framework of the quantum tunneling method. We find the same expression for the Hawking temperatures associated with the tunneling of both massive vector and scalar particles, and show this expression to be proportional to the velocity of the warp drive. On the other hand, since the discovery of gravitational waves, the quasinormal modes (QNMs) of black holes have also been extensively studied. With this purpose in mind, we perform a QNM analysis of massive scalar field perturbations in the background of the eternal-Alcubierre-warp-drive spacetime. Our analytical analysis shows that massive scalar perturbations lead to stable QNMs.

Linking the Unitary Paradigm to Policy through a Synthesis of Caring Science and Integrative Nursing.

Science.gov (United States)

Koithan, Mary S; Kreitzer, Mary Jo; Watson, Jean

2017-07-01

The principles of integrative nursing and caring science align with the unitary paradigm in a way that can inform and shape nursing knowledge, patient care delivery across populations and settings, and new healthcare policy. The proposed policies may transform the healthcare system in a way that supports nursing praxis and honors the discipline's unitary paradigm. This call to action provides a distinct and hopeful vision of a healthcare system that is accessible, equitable, safe, patient-centered, and affordable. In these challenging times, it is the unitary paradigm and nursing wisdom that offer a clear path forward.

Realization of a unique time evolution unitary operator in Klein Gordon theory

International Nuclear Information System (INIS)

Balasubramanian, T.S.; Bhatia, S.Kr.

1986-01-01

The scattering theory for the Klein Gordon equation, with time-dependent potential and in a non-static space-time, is considered. Using the Klein Gordon equation formulated in the Hilbert space L 2 (R 3 ) and the Einstein's relativistic equation in the space L 2 (R 3 ,dx) and establishing the equivalence of the vacuum states of their linearized forms in the Hilbert space L 2 (R 3 ) with the help of unique symmetric symplectic operator, the time evolution unitary operator U(t) has been fixed for the Klein Gordon eqution, incorporating either the positive or negative frequencies, in the infinite dimensional Hilbert space L 2 (R 3 ). (author)

Non unitarity effects in the time evolution of one body observables

International Nuclear Information System (INIS)

Nemes, M.C.; Toledo Piza, A.F.R. de

1982-01-01

We present a formal derivation of the exact dynamics of the one body density matrix. Its essential ingredients are shown to be: a) a mean field unitary time evolution, b) irreducible non unitary corrections to it (collision effects) and c) the time evolution of initial state correlations (which contributes to both a) and b). The qualitative importance of collision effects to the expectation value of one body operators is discussed and a quantitative study is carried out within the framework of an exactly soluble model, the non unitary contributions vary from 10% to over 100%

Chiral fermions in asymptotically safe quantum gravity.

Science.gov (United States)

Meibohm, J; Pawlowski, J M

2016-01-01

We study the consistency of dynamical fermionic matter with the asymptotic safety scenario of quantum gravity using the functional renormalisation group. Since this scenario suggests strongly coupled quantum gravity in the UV, one expects gravity-induced fermion self-interactions at energies of the Planck scale. These could lead to chiral symmetry breaking at very high energies and thus to large fermion masses in the IR. The present analysis which is based on the previous works (Christiansen et al., Phys Rev D 92:121501, 2015; Meibohm et al., Phys Rev D 93:084035, 2016), concludes that gravity-induced chiral symmetry breaking at the Planck scale is avoided for a general class of NJL-type models. We find strong evidence that this feature is independent of the number of fermion fields. This finding suggests that the phase diagram for these models is topologically stable under the influence of gravitational interactions.

Dynamics of Three-Body Correlations in Quenched Unitary Bose Gases

Science.gov (United States)

Colussi, V. E.; Corson, J. P.; D'Incao, J. P.

2018-03-01

We investigate dynamical three-body correlations in the Bose gas during the earliest stages of evolution after a quench to the unitary regime. The development of few-body correlations is theoretically observed by determining the two- and three-body contacts. We find that the growth of three-body correlations is gradual compared to two-body correlations. The three-body contact oscillates coherently, and we identify this as a signature of Efimov trimers. We show that the growth of three-body correlations depends nontrivially on parameters derived from both the density and Efimov physics. These results demonstrate the violation of scaling invariance of unitary bosonic systems via the appearance of log-periodic modulation of three-body correlations.

Observation of three-component fermions in the topological semimetal molybdenum phosphide

Science.gov (United States)

Lv, B. Q.; Feng, Z.-L.; Xu, Q.-N.; Gao, X.; Ma, J.-Z.; Kong, L.-Y.; Richard, P.; Huang, Y.-B.; Strocov, V. N.; Fang, C.; Weng, H.-M.; Shi, Y.-G.; Qian, T.; Ding, H.

2017-06-01

In quantum field theory, Lorentz invariance leads to three types of fermion—Dirac, Weyl and Majorana. Although the existence of Weyl and Majorana fermions as elementary particles in high-energy physics is debated, all three types of fermion have been proposed to exist as low-energy, long-wavelength quasiparticle excitations in condensed-matter systems. The existence of Dirac and Weyl fermions in condensed-matter systems has been confirmed experimentally, and that of Majorana fermions is supported by various experiments. However, in condensed-matter systems, fermions in crystals are constrained by the symmetries of the 230 crystal space groups rather than by Lorentz invariance, giving rise to the possibility of finding other types of fermionic excitation that have no counterparts in high-energy physics. Here we use angle-resolved photoemission spectroscopy to demonstrate the existence of a triply degenerate point in the electronic structure of crystalline molybdenum phosphide. Quasiparticle excitations near a triply degenerate point are three-component fermions, beyond the conventional Dirac-Weyl-Majorana classification, which attributes Dirac and Weyl fermions to four- and two-fold degenerate points, respectively. We also observe pairs of Weyl points in the bulk electronic structure of the crystal that coexist with the three-component fermions. This material thus represents a platform for studying the interplay between different types of fermions. Our experimental discovery opens up a way of exploring the new physics of unconventional fermions in condensed-matter systems.

Optimal control landscape for the generation of unitary transformations with constrained dynamics

International Nuclear Information System (INIS)

Hsieh, Michael; Wu, Rebing; Rabitz, Herschel; Lidar, Daniel

2010-01-01

The reliable and precise generation of quantum unitary transformations is essential for the realization of a number of fundamental objectives, such as quantum control and quantum information processing. Prior work has explored the optimal control problem of generating such unitary transformations as a surface-optimization problem over the quantum control landscape, defined as a metric for realizing a desired unitary transformation as a function of the control variables. It was found that under the assumption of nondissipative and controllable dynamics, the landscape topology is trap free, which implies that any reasonable optimization heuristic should be able to identify globally optimal solutions. The present work is a control landscape analysis, which incorporates specific constraints in the Hamiltonian that correspond to certain dynamical symmetries in the underlying physical system. It is found that the presence of such symmetries does not destroy the trap-free topology. These findings expand the class of quantum dynamical systems on which control problems are intrinsically amenable to a solution by optimal control.

Exotic fermions and electric dipole moments

International Nuclear Information System (INIS)

Joshipura, A.S.

1991-01-01

The contributions of mirror fermions to the electric dipole moments (EDM's) of leptons and neutrons are studied using the available limits on the mixing of the relevant fermions to their mirror partners. These limits imply EDM's several orders of magnitude larger than the current experimental bounds in the case of the electron and the neutron if the relevant CP-violating phases are not unnaturally small. If these phases are large, then the bounds on the EDM's can be used to improve upon the limits on mixing between the ordinary (f) and the mirror (F) fermions. In the specific case of the latter mixing angle being given by (m f /M F ) 1/2 , one can obtain the electron and the neutron EDM's close to experimental bounds

Vacuum polarization and chiral lattice fermions

International Nuclear Information System (INIS)

Randjbar Daemi, S.; Strathdee, J.

1995-09-01

The vacuum polarization due to chiral fermions on a 4-dimensional Euclidean lattice is calculated according to the overlap prescription. The fermions are coupled to weak and slowly varying background gauge and Higgs fields, and the polarization tensor is given by second order perturbation theory. In this order the overlap constitutes a gauge invariant regularization of the fermion vacuum amplitude. Its low energy - long wavelength behaviour can be computed explicitly and we verify that it coincides with the Feynman graph result obtainable, for example, by dimensional regularization of continuum gauge theory. In particular, the Standard Model Callan-Symanzik, RG functions are recovered. Moreover, there are no residual lattice artefacts such as a dependence on Wilson-type mass parameters. (author). 16 refs

Fermionic constructions of exceptional Kac-Moody algebras

International Nuclear Information System (INIS)

Schwimmer, A.

1985-01-01

The author discusses the fermionic representations of SO(2n) Kac Moody algebras. He describes construction of the E/sub 8/ algebra in terms of free fermionic operators, and generalises procedures for the basic representations of the Kac-Moody algebras appearing in Freudenthal's magic square

Path-integral formulation of chiral invariant fermion models in two dimensions

International Nuclear Information System (INIS)

Furuya, K.; Gamboa Saravi, R.E.; Schaposnik, F.A.

1982-01-01

We study the Thirring and chiral-invariant Gross-Neveu (CGN) models using the functional integral method. By introducing an auxiliary vector field we disclose a relation with two-dimensional gauge theories coupled to fermions and then extend a technique based on a chiral change in the functional variables to study purely fermionic models. We obtain the exact Klaiber solution for the massless Thirring model (for spin 1/2) in a very simple way and we then extend our technique to investigate the CGN model. We show the factorization of a free fermionic part at the level of Green functions on very general grounds. We then impose certain restrictions on the behavior of the fields - which render our treatment exact only in the zero winding number sector, but allow the computation of the U(1) part of the CGN Green functions exactly, showing, in particular, its complete decoupling from the color part and the almost long-range order behavior in the infrared region. In our approach, the non-triviality of the jacobian arising from the chiral transformation - directly related to the topological density and the axial anomaly - appears to be crucial for the functional integral treatment of these models. (orig.)

Two-dimensional thermofield bosonization II: Massive fermions

International Nuclear Information System (INIS)

Amaral, R.L.P.G.; Belvedere, L.V.; Rothe, K.D.

2008-01-01

We consider the perturbative computation of the N-point function of chiral densities of massive free fermions at finite temperature within the thermofield dynamics approach. The infinite series in the mass parameter for the N-point functions are computed in the fermionic formulation and compared with the corresponding perturbative series in the interaction parameter in the bosonized thermofield formulation. Thereby we establish in thermofield dynamics the formal equivalence of the massive free fermion theory with the sine-Gordon thermofield model for a particular value of the sine-Gordon parameter. We extend the thermofield bosonization to include the massive Thirring model

Three-dimensional Majorana fermions in chiral superconductors.

Science.gov (United States)

Kozii, Vladyslav; Venderbos, Jörn W F; Fu, Liang

2016-12-01

Using a systematic symmetry and topology analysis, we establish that three-dimensional chiral superconductors with strong spin-orbit coupling and odd-parity pairing generically host low-energy nodal quasiparticles that are spin-nondegenerate and realize Majorana fermions in three dimensions. By examining all types of chiral Cooper pairs with total angular momentum J formed by Bloch electrons with angular momentum j in crystals, we obtain a comprehensive classification of gapless Majorana quasiparticles in terms of energy-momentum relation and location on the Fermi surface. We show that the existence of bulk Majorana fermions in the vicinity of spin-selective point nodes is rooted in the nonunitary nature of chiral pairing in spin-orbit-coupled superconductors. We address experimental signatures of Majorana fermions and find that the nuclear magnetic resonance spin relaxation rate is significantly suppressed for nuclear spins polarized along the nodal direction as a consequence of the spin-selective Majorana nature of nodal quasiparticles. Furthermore, Majorana nodes in the bulk have nontrivial topology and imply the presence of Majorana bound states on the surface, which form arcs in momentum space. We conclude by proposing the heavy fermion superconductor PrOs 4 Sb 12 and related materials as promising candidates for nonunitary chiral superconductors hosting three-dimensional Majorana fermions.

On the exchange term of the interacting boson-fermion hamiltonian

International Nuclear Information System (INIS)

Gelberg, A.

1983-01-01

The exchange term of the Interacting Boson Fermion Model is investigated by using I. Talmi's method based on the shell model. A quadrupole operator of a three-proton system is formed; the protons are quadrupole-coupled to the neutron-bosons. Seniority conserving and seniority non conserving terms are considered. The particle number dependence of the parameters is investigated for the single-j shell. The relation between exchange and direct, seniority non conserving terms is examined. Approximate formulas are given for the multi-j shell. (orig.)

Stochastic integration of the Bethe-Salpeter equation for two bound fermions

International Nuclear Information System (INIS)

Salomon, M.

1988-09-01

A non-perturbative method using a Monte Carlo algorithm is used to integrate the Bethe-Salpeter equation in momentum space. Solutions for two scalars and two fermions with an arbitrary coupling constant are calculated for bound states in the ladder approximation. The results are compared with other numerical methods. (Author) (13 refs., 2 figs.)

Spin-dependent level density in interacting Boson-Fermion-Fermion model of the Odd-Odd Nucleus 196Au

International Nuclear Information System (INIS)

Kabashi, S.; Bekteshi, S.; Ahmetaj, S.; Shaqiri, Z.

2009-01-01

The level density of the odd-odd nucleus 196 Au is investigated in the interacting boson-fermion-fermion model (IBFFM) which accounts for collectivity and complex interaction between quasiparticle and collective modes.The IBFFM spin-dependent level densities show high-spin reduction with respect to Bethe formula.This can be well accounted for by a modified spin-dependent level density formula. (authors)

Strong correlations in few-fermion systems

Energy Technology Data Exchange (ETDEWEB)

Bergschneider, Andrea

2017-07-26

In this thesis, I report on the deterministic preparation and the observation of strongly correlated few-fermion systems in single and double-well potentials. In a first experiment, we studied a system of one impurity interacting with a number of majority atoms which we prepared in a single potential well in the one-dimensional limit. With increasing number of majority particles, we observed a decrease in the quasi-particle residue which is in agreement with expectations from the Anderson orthogonality catastrophe. In a second experiment, we prepared two fermions in a double-well potential which represents the fundamental building block of the Fermi-Hubbard model. By increasing the repulsion between the two fermions, we observed the crossover into the antiferromagnetic Mott-insulator regime. Furthermore, I describe a new imaging technique, which allows spin-resolved single-atom detection both in in-situ and in time-of-flight. We use this technique to investigate the emergence of momentum correlations of two repulsive fermions in the ground state of the double well. With the methods developed in this thesis, we have established a framework for quantum simulation of strongly correlated many-body systems in tunable potentials.

Pole mass, width, and propagators of unstable fermions

International Nuclear Information System (INIS)

Kniehl, B.A.; Sirlin, A.

2008-01-01

The concepts of pole mass and width are extended to unstable fermions in the general framework of parity-nonconserving gauge theories, such as the Standard Model. In contrast with the conventional on-shell definitions, these concepts are gauge independent and avoid severe unphysical singularities, properties of great importance since most fundamental fermions in nature are unstable particles. General expressions for the unrenormalized and renormalized dressed propagators of unstable fermions and their field-renormalization constants are presented. (orig.)

Free Fermions and the Classical Compact Groups

Science.gov (United States)

Cunden, Fabio Deelan; Mezzadri, Francesco; O'Connell, Neil

2018-06-01

There is a close connection between the ground state of non-interacting fermions in a box with classical (absorbing, reflecting, and periodic) boundary conditions and the eigenvalue statistics of the classical compact groups. The associated determinantal point processes can be extended in two natural directions: (i) we consider the full family of admissible quantum boundary conditions (i.e., self-adjoint extensions) for the Laplacian on a bounded interval, and the corresponding projection correlation kernels; (ii) we construct the grand canonical extensions at finite temperature of the projection kernels, interpolating from Poisson to random matrix eigenvalue statistics. The scaling limits in the bulk and at the edges are studied in a unified framework, and the question of universality is addressed. Whether the finite temperature determinantal processes correspond to the eigenvalue statistics of some matrix models is, a priori, not obvious. We complete the picture by constructing a finite temperature extension of the Haar measure on the classical compact groups. The eigenvalue statistics of the resulting grand canonical matrix models (of random size) corresponds exactly to the grand canonical measure of free fermions with classical boundary conditions.

Free Fermions and the Classical Compact Groups

Science.gov (United States)

Cunden, Fabio Deelan; Mezzadri, Francesco; O'Connell, Neil

2018-04-01

There is a close connection between the ground state of non-interacting fermions in a box with classical (absorbing, reflecting, and periodic) boundary conditions and the eigenvalue statistics of the classical compact groups. The associated determinantal point processes can be extended in two natural directions: (i) we consider the full family of admissible quantum boundary conditions (i.e., self-adjoint extensions) for the Laplacian on a bounded interval, and the corresponding projection correlation kernels; (ii) we construct the grand canonical extensions at finite temperature of the projection kernels, interpolating from Poisson to random matrix eigenvalue statistics. The scaling limits in the bulk and at the edges are studied in a unified framework, and the question of universality is addressed. Whether the finite temperature determinantal processes correspond to the eigenvalue statistics of some matrix models is, a priori, not obvious. We complete the picture by constructing a finite temperature extension of the Haar measure on the classical compact groups. The eigenvalue statistics of the resulting grand canonical matrix models (of random size) corresponds exactly to the grand canonical measure of free fermions with classical boundary conditions.

Coherent states in the fermionic Fock space

International Nuclear Information System (INIS)

Oeckl, Robert

2015-01-01

We construct the coherent states in the sense of Gilmore and Perelomov for the fermionic Fock space. Our treatment is from the outset adapted to the infinite-dimensional case. The fermionic Fock space becomes in this way a reproducing kernel Hilbert space of continuous holomorphic functions. (paper)

Nambu-Jona-Lasinio model with Wilson fermions

DEFF Research Database (Denmark)

Rantaharju, Jarno; Drach, Vincent; Pica, Claudio

2017-01-01

We present a lattice study of a Nambu-Jona-Lasinio (NJL) model using Wilson fermions. Four-fermion interactions are a natural part of several extensions of the Standard Model, appearing as a low-energy description of a more fundamental theory. In models of dynamical electroweak symmetry breaking...

On the disordered fermion couplings

International Nuclear Information System (INIS)

Bernaschi, M.; Cabasino, S.; Marinari, E.; Rome-2 Univ.; Sarno, R.; Rome-1 Univ.

1989-01-01

We study the possibility of avoiding the fermion doubling problem by using a random coupling. We use numerical simulations in order to study the theory in the strong disorder region. We find a sharp crossover as a function of the strength of the disorder. For weak quenched disorder we find that the species doubling survives, while for strong quenched disorder only with a particular choice of the random term (antihermitian) it is possible to get a theory that seems to avoid fermion doubling. (orig.)

Fermions as generalized Ising models

Directory of Open Access Journals (Sweden)

C. Wetterich

2017-04-01

Full Text Available We establish a general map between Grassmann functionals for fermions and probability or weight distributions for Ising spins. The equivalence between the two formulations is based on identical transfer matrices and expectation values of products of observables. The map preserves locality properties and can be realized for arbitrary dimensions. We present a simple example where a quantum field theory for free massless Dirac fermions in two-dimensional Minkowski space is represented by an asymmetric Ising model on a euclidean square lattice.

Coulomb’s law corrections and fermion field localization in a tachyonic de Sitter thick braneworld

International Nuclear Information System (INIS)

Cartas-Fuentevilla, Roberto; Escalante, Alberto; Germán, Gabriel; Herrera-Aguilar, Alfredo; Mora-Luna, Refugio Rigel

2016-01-01

Following recent studies which show that it is possible to localize gravity as well as scalar and gauge vector fields in a tachyonic de Sitter thick braneworld, we investigate the solution of the gauge hierarchy problem, the localization of fermion fields in this model, the recovering of the Coulomb law on the non-relativistic limit of the Yukawa interaction between bulk fermions and gauge bosons localized in the brane, and confront the predicted 5D corrections to the photon mass with its upper experimental/observational bounds, finding the model physically viable since it passes these tests. In order to achieve the latter aims we first consider the Yukawa interaction term between the fermionic and the tachyonic scalar fields MF(T)ΨΨ-bar in the action and analyze four distinct tachyonic functions F(T) that lead to four different structures of the respective fermionic mass spectra with different physics. In particular, localization of the massless left-chiral fermion zero mode is possible for three of these cases. We further analyze the phenomenology of these Yukawa interactions among fermion fields and gauge bosons localized on the brane and obtain the crucial and necessary information to compute the corrections to Coulomb’s law coming from massive KK vector modes in the non-relativistic limit. These corrections are exponentially suppressed due to the presence of the mass gap in the mass spectrum of the bulk gauge vector field. From our results we conclude that corrections to Coulomb’s law in the thin brane limit have the same form (up to a numerical factor) as far as the left-chiral massless fermion field is localized on the brane. Finally we compute the corrections to the Coulomb’s law for an arbitrarily thick brane scenario which can be interpreted as 5D corrections to the photon mass. By performing consistent estimations with brane phenomenology, we found that the predicted corrections to the photon mass, which are well bounded by the experimentally

Coulomb’s law corrections and fermion field localization in a tachyonic de Sitter thick braneworld

Energy Technology Data Exchange (ETDEWEB)

Cartas-Fuentevilla, Roberto; Escalante, Alberto [Instituto de Física, Benemérita Universidad Autónoma de Puebla,Apdo. postal J-48, 72570 Puebla, Pue. (Mexico); Germán, Gabriel [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México,Apdo. Postal 48-3, 62251 Cuernavaca, Morelos (Mexico); Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road,Oxford, OX1 3NP (United Kingdom); Herrera-Aguilar, Alfredo [Instituto de Física, Benemérita Universidad Autónoma de Puebla,Apdo. postal J-48, 72570 Puebla, Pue. (Mexico); Institutode Física y Matemáticas, Universidad Michoacana de San Nicolás de Hidalgo,Edificio C-3, Ciudad Universitaria, CP 58040, Morelia, Michoacán (Mexico); Mora-Luna, Refugio Rigel [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México,Apdo. Postal 48-3, 62251 Cuernavaca, Morelos (Mexico)

2016-05-11

Following recent studies which show that it is possible to localize gravity as well as scalar and gauge vector fields in a tachyonic de Sitter thick braneworld, we investigate the solution of the gauge hierarchy problem, the localization of fermion fields in this model, the recovering of the Coulomb law on the non-relativistic limit of the Yukawa interaction between bulk fermions and gauge bosons localized in the brane, and confront the predicted 5D corrections to the photon mass with its upper experimental/observational bounds, finding the model physically viable since it passes these tests. In order to achieve the latter aims we first consider the Yukawa interaction term between the fermionic and the tachyonic scalar fields MF(T)ΨΨ-bar in the action and analyze four distinct tachyonic functions F(T) that lead to four different structures of the respective fermionic mass spectra with different physics. In particular, localization of the massless left-chiral fermion zero mode is possible for three of these cases. We further analyze the phenomenology of these Yukawa interactions among fermion fields and gauge bosons localized on the brane and obtain the crucial and necessary information to compute the corrections to Coulomb’s law coming from massive KK vector modes in the non-relativistic limit. These corrections are exponentially suppressed due to the presence of the mass gap in the mass spectrum of the bulk gauge vector field. From our results we conclude that corrections to Coulomb’s law in the thin brane limit have the same form (up to a numerical factor) as far as the left-chiral massless fermion field is localized on the brane. Finally we compute the corrections to the Coulomb’s law for an arbitrarily thick brane scenario which can be interpreted as 5D corrections to the photon mass. By performing consistent estimations with brane phenomenology, we found that the predicted corrections to the photon mass, which are well bounded by the experimentally

Electron electric dipole moment in mirror fermion model with electroweak scale non-sterile right-handed neutrinos

Directory of Open Access Journals (Sweden)

Chia-Feng Chang

2018-03-01

Full Text Available The electric dipole moment of the electron is studied in detail in an extended mirror fermion model with the following unique features of (a right-handed neutrinos are non-sterile and have masses at the electroweak scale, and (b a horizontal symmetry of the tetrahedral group is used in the lepton and scalar sectors. We study the constraint on the parameter space of the model imposed by the latest ACME experimental limit on electron electric dipole moment. Other low energy experimental observables such as the anomalous magnetic dipole moment of the muon, charged lepton flavor violating processes like muon decays into electron plus photon and muon-to-electron conversion in titanium, gold and lead are also considered in our analysis for comparison. In addition to the well-known CP violating Dirac and Majorana phases in the neutrino mixing matrix, the dependence of additional phases of the new Yukawa couplings in the model is studied in detail for all these low energy observables.

Electron electric dipole moment in mirror fermion model with electroweak scale non-sterile right-handed neutrinos

Science.gov (United States)

Chang, Chia-Feng; Hung, P. Q.; Nugroho, Chrisna Setyo; Tran, Van Que; Yuan, Tzu-Chiang

2018-03-01

The electric dipole moment of the electron is studied in detail in an extended mirror fermion model with the following unique features of (a) right-handed neutrinos are non-sterile and have masses at the electroweak scale, and (b) a horizontal symmetry of the tetrahedral group is used in the lepton and scalar sectors. We study the constraint on the parameter space of the model imposed by the latest ACME experimental limit on electron electric dipole moment. Other low energy experimental observables such as the anomalous magnetic dipole moment of the muon, charged lepton flavor violating processes like muon decays into electron plus photon and muon-to-electron conversion in titanium, gold and lead are also considered in our analysis for comparison. In addition to the well-known CP violating Dirac and Majorana phases in the neutrino mixing matrix, the dependence of additional phases of the new Yukawa couplings in the model is studied in detail for all these low energy observables.

A novel and economical explanation for SM fermion masses and mixings

Energy Technology Data Exchange (ETDEWEB)

Hernandez, A.E.C. [Universidad Tecnica Federico Santa Maria and Centro Cientifico-Tecnologico de Valparaiso, Valparaiso (Chile)

2016-09-15

I propose the first multiscalar singlet extension of the standard model (SM), which generates tree level top quark and exotic fermion masses as well as one and three loop level masses for charged fermions lighter than the top quark and for light active neutrinos, respectively, without invoking electrically charged scalar fields. That model, which is based on the S{sub 3} x Z{sub 8} discrete symmetry, successfully explains the observed SM fermion mass and mixing pattern. The charged exotic fermions induce one loop level masses for charged fermions lighter than the top quark. The Z{sub 8} charged scalar singlet χ generates the observed charged fermion mass and quark mixing pattern. (orig.)

Theoretical princi les of constructing the equations of motion for a spin color-charged particle in gauge and fermion fields

Science.gov (United States)

Markov, Yu. A.; Shishmarev, A. A.

2010-11-01

Based on the most general principles of materiality, gauge, and re-parameterized invariance, the problem of constructing an action describing the dynamics of a classical color-charged particle moving in external non-Abelian gauge and fermion fields is considered. The case of a linear Lagrangian dependence on the external fermion fields is discussed. Within the framework of the description of the color degree of freedom of the particle with half-integer spin by the Grassmann color charges, a new concept of the Grassmann color source of the particle being a fermion analog of the conventional color current is introduced.

Searches for Fourth Generation Fermions

Energy Technology Data Exchange (ETDEWEB)

Ivanov, A.; /Fermilab

2011-09-01

We present the results from searches for fourth generation fermions performed using data samples collected by the CDF II and D0 Detectors at the Fermilab Tevatron p{bar p} collider. Many of these results represent the most stringent 95% C. L. limits on masses of new fermions to-date. A fourth chiral generation of massive fermions with the same quantum numbers as the known fermions is one of the simplest extensions of the SM with three generations. The fourth generation is predicted in a number of theories, and although historically have been considered disfavored, stands in agreement with electroweak precision data. To avoid Z {yields} {nu}{bar {nu}} constraint from LEP I a fourth generation neutrino {nu}{sub 4} must be heavy: m({nu}{sub 4}) > m{sub Z}/2, where m{sub Z} is the mass of Z boson, and to avoid LEP II bounds a fourth generation charged lepton {ell}{sub 4} must have m({ell}{sub 4}) > 101 GeV/c{sup 2}. At the same time due to sizeable radiative corrections masses of fourth generation fermions cannot be much higher the current lower bounds and masses of new heavy quarks t' and b' should be in the range of a few hundred GeV/c{sup 2}. In the four-generation model the present bounds on the Higgs are relaxed: the Higgs mass could be as large as 1 TeV/c{sup 2}. Furthermore, the CP violation is significantly enhanced to the magnitude that might account for the baryon asymmetry in the Universe. Additional chiral fermion families can also be accommodated in supersymmetric two-Higgs-doublet extensions of the SM with equivalent effect on the precision fit to the Higgs mass. Another possibility is heavy exotic quarks with vector couplings to the W boson Contributions to radiative corrections from such quarks with mass M decouple as 1/M{sup 2} and easily evade all experimental constraints. At the Tevatron p{bar p} collider 4-th generation chiral or vector-like quarks can be either produced strongly in pairs or singly via electroweak production, where the