5,696 research outputs found
Magnetic effects on spontaneous symmetry breaking/restoration in a toroidal topology
We study temperature and finite-size effects on the spontaneous symmetry
breaking/restoration for a scalar field model under the influence of an
external magnetic field, at finite chemical potential. We use the 2PI formalism
and consider the large- limit. We find that there is a minimal size of the
system to sustain the broken phase, which diminishes as the applied field
increases but is independent of the chemical potential. We analyze the critical
curves and show that the magnetic field enhances the broken-phase regions,
while increasing the chemical potential leads to a diminishement of the
critical temperature.Comment: Five pages, five figures, version as accepted for publication in
Phys. Rev.
Large-N transition temperature for superconducting films in a magnetic field
We consider the -component Ginzburg-Landau model in the large limit,
the system being embedded in an external constant magnetic field and confined
between two parallel planes a distance apart from one another. On physical
grounds, this corresponds to a material in the form of a film in the presence
of an external magnetic field. Using techniques from dimensional and
-function regularization, modified by the external field and the
confinement conditions, we investigate the behavior of the system as a function
of the film thickness . This behavior suggests the existence of a minimal
critical thickness below which superconductivity is suppressed.Comment: Revtex, two column, 4 pages, 2 figure
Gauge Fluctuations in Superconducting Films
In this paper we consider a superconducting film modeled by the
Ginzburg-Landau model, confined between two parallel planes a distance
apart from one another. Our approach is based on the Gaussian effective
potential in the transverse unitarity gauge, which allows to treat gauge
contributions in a compact form. Using techniques from dimensional and
-function regularizations, modified by the confinement conditions, we
investigate the critical temperature as a function of the film thickness .
The contributions from the scalar self-interaction and from the gauge
fluctuations are clearly identified. The model suggests the existence of a
minimal critical thickness below which superconductivity is suppressed.Comment: 6 pages Revtex, no figure
Critical behaviour of the compactified theory
We investigate the critical behaviour of the -component Euclidean model at leading order in -expansion. We consider it in
three situations: confined between two parallel planes a distance apart
from one another, confined to an infinitely long cylinder having a square
cross-section of area and to a cubic box of volume . Taking the mass
term in the form , we retrieve Ginzburg-Landau
models which are supposed to describe samples of a material undergoing a phase
transition, respectively in the form of a film, a wire and of a grain, whose
bulk transition temperature () is known. We obtain equations for the
critical temperature as functions of (film), (wire), (grain) and of
, and determine the limiting sizes sustaining the transition.Comment: 12 pages, no figure
Phase transition in the 3-D massive Gross-Neveu model
We consider the 3-dimensional massive Gross-Neveu model at finite temperature
as an effective theory for strong interactions. Using the Matsubara imaginary
time formalism, we derive a closed form for the renormalized -dependent
four-point function. This gives a singularity, suggesting a phase transition.
Considering the free energy we obtain the -dependent mass, which goes to
zero for some temperature. These results lead us to the conclusion that there
is a second-order phase transition.Comment: 06 pages, 02 figures, LATE
A note on the infrared behavior of the compactified Ginzburg--Landau model in a magnetic field
We consider the Euclidean large- Ginzburg--Landau model in dimensions,
() of them being compactified. For D=3, the system can be supposed
to describe, in the cases of d=1, d=2, and d=3, respectively, a superconducting
material in the form of a film, of an infinitely long wire having a rectangular
cross-section and of a brick-shaped grain. We investigate the fixed-point
structure of the model, in the presence of an external magnetic field. An
infrared-stable fixed points is found, which is independent of the number of
compactified dimensions. This generalizes previous work for type-II
superconducting filmsComment: LATEX, 6 pages no figures. arXiv admin note: 80% of text overlaps
with arXiv:1102.139
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