6 research outputs found
Threshold Effects And Perturbative Unification
We discuss the effect of the renormalization procedure in the computation of
the unification point for running coupling constants. We explore the effects of
threshold--crossing on the --functions. We compute the running of the
coupling constants of the Standard Model, between and , using a mass
dependent subtraction procedure, and then compare the results with ,
and with the -- function approximation. We also do this for the Minimal
Supersymmetric extension of the Standard Model. In the latter, the bounds on
susy masses that one obtains by requiring perturbative unification are
dependent, to some extent, on the procedure.Comment: 22 pages, REVTEX-2.1, 6 Post-Script figures are include
Path-integral fermion-boson decoupling at finite temperature
We show how to extend the standard functional approach to bosonisation, based
on a decoupling change of path-integral variables, to the case in which a
finite temperature is considered. As examples, in order to both illustrate and
check the procedure, we derive the thermodynamical partition functions for the
Thirring and Schwinger models.Comment: 12 pages, latex, no figure
Corner wetting in a far-from-equilibrium magnetic growth model
The irreversible growth of magnetic films is studied in three-dimensional
confined geometries of size , where is the growing
direction. Competing surface magnetic fields, applied to opposite corners of
the growing system, lead to the observation of a localization-delocalization
(weakly rounded) transition of the interface between domains of up and down
spins on the planes transverse to the growing direction. This effective
transition is the precursor of a true far-from-equilibrium corner wetting
transition that takes place in the thermodynamic limit. The phenomenon is
characterized quantitatively by drawing a magnetic field-temperature phase
diagram, firstly for a confined sample of finite size, and then by
extrapolating results, obtained with samples of different size, to the
thermodynamic limit. The results of this work are a nonequilibrium realization
of analogous phenomena recently investigated in equilibrium systems, such as
corner wetting transitions in the Ising model.Comment: 14 pages, 8 figures. EPJ styl
Self-dual Ginzburg-Landau vortices in a disk
We study the properties of the Ginzburg-Laundau model in the self-dual point
for a two-dimensional finite system . By a numerical calculation we analyze the
solutions of the Euler-Lagrange equations for a cylindrically symmetric ansatz.
We also study the self-dual equations for this case. We find that the minimal
energy configurations are not given by the Bogomol'nyi equations but by
solutions to the Euler Lagrange ones. With a simple approximation scheme we
reproduce the result of the numerical calculation.Comment: 8 pages, 4 figures, RevTex macro
Multiflavor Correlation Functions in non-Abelian Gauge Theories at Finite Density in two dimensions
We compute vacuum expectation values of products of fermion bilinears for
two-dimensional Quantum Chromodynamics at finite flavored fermion densities. We
introduce the chemical potential as an external charge distribution within the
path-integral approach and carefully analyse the contribution of different
topological sectors to fermion correlators. We show the existence of chiral
condensates exhibiting an oscillatory inhomogeneous behavior as a function of a
chemical potential matrix. This result is exact and goes in the same direction
as the behavior found in QCD_4 within the large N approximation.Comment: 28 pages Latex (3 pages added and other minor changes) to appear in
Phys.Rev.
Friedel oscillations in a Luttinger liquid with long-range interactions
We introduce a path-integral approach that allows to compute charge density
oscillations in a Luttinger liquid with impurities. We obtain an explicit
expression for the envelope of Friedel oscillations in the presence of
arbitrary electron-electron potentials. As examples, in order to illustrate the
procedure, we show how to use our formula for contact and Coulomb potentials.Comment: 11 pages, no figures, latex. Revised version to appear in PR