Comment on "Light-front Schwinger model at finite temperature"

In a recent paper by A. Das and X. Zhou [Phys. Rev. D 68, 065017 (2003)] it is claimed that explicit evaluation of the thermal photon self-energy in the Schwinger model gives off-shell thermal Green functions that are different in light-front and conventional quantizations. We show that the claimed difference originates from an erroneous simplification of the fermion propagator used in the light-front calculation.Comment: 8 pages, revtex4, added section refuting the massless limit proposed in hep-th/031102

Specific heat of Bosons in a lattice

We present a theoretical study of specific heat of bosons ($C_v$) in a simple cubic lattice. We have studied the non-interacting bosons and the Tonks gas. For both cases, the $C_v$ above the bose condensation temperature shows considerable temperature dependence compared to that of free bosons. For Tonks gas, we find that the low-temperature specific heat increases as the system gets closer to the Mott transition

An extended pair tunneling model: studies on bilayer splitting and some superconducting state properties

We consider an extended version of the pair tunneling model including interlayer single particle hopping (ISPH) as a complementary process to pair tunneling. The normal state gap, as found in cuprates, is taken to suppress the effective ISPH in conformity with the experimental observations, and this in turn enhances the pair tunneling process. The effective ISPH involves a probability factor P for which we consider two choices and provide phenomenological arguments in favour of them. We address the issue of bilayer splitting by calculating the spectral density function and corresponding photoemission intensity curves and show that our calculations conform with the absence of bilayer splitting observed in ARPES experiments on Bi2212. We have also studied the temperature variation of the superconducting gap and ratio of the superconducting gap to T_c. Our results, obtained for both the choices of P, are reasonably in good agreement with those from experiments on cuprate superconductors. A linear T-dependent choice of P, however, yields a precise match to the experimantal data of the temperature varying superconducting gap.Comment: Latex file, 17 pages, 5 figures (postscript files) include

Vanishing magnetic mass in QED3_{3} with a Chern-Simons term

We show that, at one loop, the magnetic mass vanishes at finite temperature in QED in any dimension. In QED$_{3}$, even the zero temperature part can be regularized to zero. We calculate the two loop contributions to the magnetic mass in QED$_{3}$ with a Chern-Simons term and show that it vanishes. We give a simple proof which shows that the magnetic mass vanishes to all orders at finite temperature in this theory. This proof also holds for QED in any dimension.Comment: revtex, 7 pages, 5 figure

Gauge invariant derivative expansion of the effective action at finite temperature and density and the scalar field in 2+1 dimensions

A method is presented for the computation of the one-loop effective action at finite temperature and density. The method is based on an expansion in the number of spatial covariant derivatives. It applies to general background field configurations with arbitrary internal symmetry group and space-time dependence. Full invariance under small and large gauge transformations is preserved without assuming stationary or Abelian fields nor fixing the gauge. The method is applied to the computation of the effective action of spin zero particles in 2+1 dimensions at finite temperature and density and in presence of background gauge fields. The calculation is carried out through second order in the number of spatial covariant derivatives. Some limiting cases are worked out.Comment: 34 pages, REVTEX, no figures. Further comments adde

Nonequilibrium Dynamics in the Complex Ginzburg-Landau Equation

We present results from a comprehensive analytical and numerical study of nonequilibrium dynamics in the 2-dimensional complex Ginzburg-Landau (CGL) equation. In particular, we use spiral defects to characterize the domain growth law and the evolution morphology. An asymptotic analysis of the single-spiral correlation function shows a sequence of singularities -- analogous to those seen for time-dependent Ginzburg-Landau (TDGL) models with O(n) symmetry, where $n$ is even.Comment: 11 pages, 5 figure

Abelian and Non-Abelian Induced Parity Breaking Terms at Finite Temperature

We compute the exact canonically induced parity breaking part of the effective action for 2+1 massive fermions in particular Abelian and non Abelian gauge field backgrounds. The method of computation resorts to the chiral anomaly of the dimensionally reduced theory.Comment: 13 pages, RevTeX, no figure

Parity Violating Bosonic Loops at Finite Temperature

The finite temperature parity-violating contributions to the polarization tensor are computed at one loop in a system without fermions. The system studied is a Maxwell-Chern-Simons-Higgs system in the broken phase, for which the parity-violating terms are well known at zero temperature. At nonzero temperature the static and long-wavelength limits of the parity violating terms have very different structure, and involve non-analytic log terms depending on the various mass scales. At high temperature the boson loop contribution to the Chern-Simons term goes like T in the static limit and like T log T in the long-wavelength limit, in contrast to the fermion loop contribution which behaves like 1/T in the static limit and like log T/T in the long wavelength limit.Comment: 10 pp, 1 fig, revte

Integrability and Conformal Symmetry in the BCS model

The exactly solvable BCS Hamiltonian of superconductivity is considered from several viewpoints: Richardson's ansatz, conformal field theory, integrable inhomogenous vertex models and Chern-Simons theory.Comment: Latex with macros included, 12 pages, Proceedings of the NATO Advanced Research Workshop on Statistical Field Theories, Como 18-23 June 2001. Editors: Andrea Cappelli and Giuseppe Mussardo. to be published by Kluwer, Academic Publishers. Corrected some typos and further acknowledgment