共查询到20条相似文献,搜索用时 31 毫秒
1.
T. Sýkora 《The European Physical Journal C - Particles and Fields》2000,14(4):699-704
We calculate the equal-time commutator of two fermionic currents within the framework of the 1+1 dimensional fully quantized
theory, describing the interaction of fermions with a vector boson. It is shown that the interaction does not change the result
obtained within the theory of free fermions.
Received: 10 November 1999 / Revised version: 20 January 2000 / Published online: 8 May 2000 相似文献
2.
T. DeGrand 《The European physical journal. Special topics》2007,152(1):1-27
Four lectures about chiral symmetry and dynamical fermions in QCD.
1) Chiral symmetry in continuum QCD with an eye toward lattice simulations. 2) Lattice fermions with exact chiral symmetry:
staggered fermions, fermions in
five dimensions, chiral fermions in four dimensions.
3) A typical lattice simulation from beginning to end: the simulation algorithm,
designing observables to measure some desired quantity, analyzing the data.
4) Recent lattice results relevant to chiral symmetry: a mini-review. 相似文献
3.
I.I. Satija 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):345-348
Disordered systems exhibiting exponential localization are mapped to anisotropic spin chains with localization length being
related to the anisotropy of the spin model. This relates localization phenomenon in fermions to the rotational symmetry breaking
in the critical spin chains. One of the intriguing consequence is that the statement of Onsager universality in spin chains
implies universality of the localized fermions where the fluctuations in localized wave functions are universal. We further
show that the fluctuations about localized nonrelativistic fermions describe relativistic fermions. This provides a new approach
to understand the absence of localization in disordered Dirac fermions. We investigate how disorder affects well known universality
of the spin chains by examining the multifractal exponents. Finally, we examine the effects of correlations on the localization
characteristics of relativistic fermions.
Received 28 September 2001 / Received in final form 30 November 2001 Published online 2 October 2002
RID="a"
ID="a"e-mail: isatija@nickel.nist.gov 相似文献
4.
M.O. Goerbig P. Lederer C. Morais Smith 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):57
Most states of the fractional quantum Hall effect may be interpreted in terms of an integral quantum Hall effect of weakly-interacting quasiparticles (composite fermions). The recently discovered state does not belong to these states because its formation is due to the residual interactions between composite fermions, which become relevant when the composite-fermion levels are only partially filled. We have derived a model of interacting composite fermions, which reveals the self-similarity of the fractional quantum Hall effect and which allows for a systematic study of higher generations of composite fermions. Here, we derive the form of the interaction potential between these hierarchical composite fermions and provide some stability criteria for such states. 相似文献
5.
G. Moortgat-Pick H. Fraas 《The European Physical Journal C - Particles and Fields》2002,25(2):189-197
The consequences of CP and CPT invariance for production and subsequent decay of Dirac and Majorana fermions in polarized fermion-antifermion annihilation
are analytically studied. We derive general symmetry relations for the production spin density matrix and for the three-particle
decay matrices and obtain constraints for the polarization and the spin-spin correlations of Dirac and Majorana fermions.
We prove that only for Majorana fermions the energy and opening angle distribution factorizes exactly into contributions from
production and decay if CP is conserved.
Received: 6 November 2001 / Revised version: 23 April 2002 / Published online: 12 July 2002 相似文献
6.
We calculate the phase diagrams at high temperature of SU(N) gauge theories with massive fermions by minimizing the one-loop effective potential. Considering fermions in the adjoint (Adj) representation at various N we observe a variety of phases when Nf2 Majorana flavours and periodic boundary conditions are applied to fermions. Also the confined phase is perturbatively accessible. For N=3, we add Fundamental (F) representation fermions with antiperiodic boundary conditions to adjoint QCD to show how the Z(3)-symmetry breaks in the confined phase. 相似文献
7.
C. Wetterich 《Annals of Physics》2010,325(12):2750-2786
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 pτ amounts to a rotation of the wave function , we infer the unitary time evolution of a quantum system of fermions according to a Schrödinger 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. 相似文献
8.
The Thomas–Fermi model at finite temperature is extended to describe a system of self-gravitating weakly interacting massive
fermions in a general-relativistic framework. The existence and properties of the gravitational phase transition in this model
are investigated numerically. It is shown that when a nondegenerate gas of weakly interacting massive fermions is cooled below
some critical temperature, a condensed phase emerges, consisting of quasidegenerate fermion stars. For fermion masses of 10
to 25 keV, these fermion stars may very well provide an alternative explanation for the supermassive compact dark objects
that are observed at galactic centers.
Received: 23 April 1999 / Revised version: 24 June 1999 / Published online: 28 September 1999 相似文献
9.
Azmi Ali Altintas 《Czechoslovak Journal of Physics》2006,56(10-11):1069-1074
We consider inhomogeneous quantum groups that transform various types of fermions: standard fermions, commuting fermions and orthofermions. These quantum groups are notq-deformations. 相似文献
10.
Kenji Maeda 《Annals of Physics》2011,(4):1032-1052
We study a many-body mixture of an equal number of bosons and two-component fermions with a strong contact attraction. In this system bosons and fermions can be paired into composite fermions. We construct a large N extension where both bosons and fermions have the extra large N degrees of freedom and the boson–fermion interaction is extended to a four-point contact interaction which is invariant under the O(N) group transformation, so that the composite fermions become singlet in terms of the O(N) group. It is shown that such O(N) singlet fields have controllable quantum fluctuations suppressed by 1/N factors and yield a systematic 1/N-expansion in terms of composite fermions. We derive an effective action described by composite fermions up to the next-to-leading-order terms in the large N expansion, and show that there can be the BCS superfluidity of composite fermions at sufficiently low temperatures. 相似文献
11.
In six different regimes for a spatial phase diagram of a trapped interacting Bose-Fermi gas mixture at low temperatures, we present the conditions for the spatial demixing and separation of bosons and fermions. Starting from a semiclassically thermodynamic model for the local density functional of thermal bosons and fermions,the explicit analytical expressions for the fugacities of bosons and fermions are derived in different regimes by means of a first-order perturbation method in a local-density approximation. The critical values of the fermionboson interaction strength as a function of the fractional composition of fermions have a general feature: increase,extreme and decrease with increasing the fermionic composition slightly above Bose-Einstein critical temperature. 相似文献
12.
Y.A. Coutinho J.A. Martins Simões C.M. Porto 《The European Physical Journal C - Particles and Fields》2001,18(4):779-784
In this paper we discuss a left–right symmetric model for elementary particles and their connection with the mass spectrum
of elementary fermions. The model is based on the group . New mirror fermions and a minimal set of Higgs particles that break this symmetry down to are proposed. The model can accommodate a consistent pattern for charged and neutral fermion masses as well as neutrino oscillations.
An important consequence of the model is that the connection between the left and right sectors can be implemented by the
neutral vector gauge boson Z and a new heavy Z'.
Received: 15 June 2000 / Revised version: 14 September 2000 / Published online: 5 February 2001 相似文献
13.
G. Grensing 《The European Physical Journal C - Particles and Fields》2002,23(2):377-387
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.
Received: 4 May 2001 / Revised version: 10 October 2001 / Published online: 8 February 2002 相似文献
14.
QCDSFUKQCD Collaboration T. Bakeyev M. Gckeler R. Horsley D. Pleiter P. E. L. Rakow G. Schierholz H. Stüben 《Physics letters. [Part B]》2004,580(3-4):197-208
By considering the local vector current between nucleon states and imposing charge conservation, we determine its renormalisation constant and quark mass improvement coefficient for Symanzik O(a) improved Wilson fermions. The computation is first performed for quenched fermions (and for completeness also with unimproved fermions) and compared against known results. The two-flavour unquenched case is then considered. 相似文献
15.
Nikodem J. Pop?awski 《General Relativity and Gravitation》2012,44(2):491-499
The observed small, positive cosmological constant may originate from a four-fermion interaction generated by the spin-torsion
coupling in the Einstein–Cartan–Sciama–Kibble gravity if the fermions are condensing. In particular, such a condensation occurs
for quark fields during the quark-gluon/hadron phase transition in the early Universe. We study how the torsion-induced four-fermion
interaction is affected by adding two terms to the Dirac Lagrangian density: the parity-violating pseudoscalar density dual
to the curvature tensor and a spinor-bilinear scalar density which measures the nonminimal coupling of fermions to torsion. 相似文献
16.
In the Einstein–Cartan theory of torsion-free gravity coupling to massless fermions, the four-fermion interaction is induced and its strength is a function of the gravitational and gauge couplings, as well as the Immirzi parameter. We study the dynamics of the four-fermion interaction to determine whether effective bilinear terms of massive fermion fields are generated. Calculating one-particle-irreducible two-point functions of fermion fields, we identify three different phases and two critical points for phase transitions characterized by the strength of four-fermion interaction: (1) chiral symmetric phase for massive fermions in strong coupling regime; (2) chiral symmetric broken phase for massive fermions in intermediate coupling regime; (3) chiral symmetric phase for massless fermions in weak coupling regime. We discuss the scaling-invariant region for an effective theory of massive fermions coupled to torsion-free gravity in the low-energy limit. 相似文献
17.
18.
Dual amplitudes of the five-point function for two fermions and three scalar bosons are constructed, and are used to obtain a consistent procedure for inclusing two fermions in the general N-point function. 相似文献
19.
C. Wetterich 《Annals of Physics》2011,(8):2243-2293
We construct a map between the quantum field theory of free Weyl or Majorana fermions and the probability distribution of a classical statistical ensemble for Ising spins or discrete bits. More precisely, a Grassmann functional integral based on a real Grassmann algebra specifies the time evolution of the real wave function qτ(t) for the Ising states τ. The time dependent probability distribution of a generalized Ising model obtains as . The functional integral employs a lattice regularization for single Weyl or Majorana spinors. We further introduce the complex structure characteristic for quantum mechanics. Probability distributions of the Ising model which correspond to one or many propagating fermions are discussed explicitly. Expectation values of observables can be computed equivalently in the classical statistical Ising model or in the quantum field theory for fermions. 相似文献
20.
L. Lavoura 《The European Physical Journal C - Particles and Fields》2003,29(2):191-195
At one-loop level the decay , where f1 and f2 are two spin-1/2 particles with the same electric charge, is mediated by a boson B and a spin-1/2 fermion F. The boson B may have either spin - interacting with the fermions through the Dirac matrices 1 and - or spin 1 - with V+A and V-A couplings to the fermions. I give general formulae for the one-loop electroweak amplitude of in all these cases.
Received: 24 February 2003 / Revised version: 26 March 2003 / Published online: 2 June 2003 相似文献