215 research outputs found
Critical behavior of 3D Z(N) lattice gauge theories at zero temperature
Three-dimensional lattice gauge theories at zero temperature are
studied for various values of . Using a modified phenomenological
renormalization group, we explore the critical behavior of the generalized
model for . Numerical computations are used to simulate
vector models for for lattices with linear extension up
to . We locate the critical points of phase transitions and establish
their scaling with . The values of the critical indices indicate that the
models with belong to the universality class of the three-dimensional
model. However, the exponent derived from the heat capacity is
consistent with the Ising universality class. We discuss a possible resolution
of this puzzle. We also demonstrate the existence of a rotationally symmetric
region within the ordered phase for all at least in the finite
volume.Comment: 25 pages, 4 figures, 8 table
The phase transitions in 2D Z(N) vector models for N>4
We investigate both analytically and numerically the renormalization group
equations in 2D Z(N) vector models. The position of the critical points of the
two phase transitions for N>4 is established and the critical index \nu\ is
computed. For N=7, 17 the critical points are located by Monte Carlo
simulations and some of the corresponding critical indices are determined. The
behavior of the helicity modulus is studied for N=5, 7, 17. Using these and
other available Monte Carlo data we discuss the scaling of the critical points
with N and some other open theoretical problems.Comment: 19 pages, 8 figures, 10 tables; version to appear on Phys. Rev.
Ghost-gluon coupling, power corrections and from twisted-mass lattice QCD at
A non-perturbative calculation of the ghost-gluon running QCD coupling
constant is performed using twisted-mass dynamical fermions. The
extraction of in the chiral limit reveals the presence of
a non-perturbative OPE contribution that is assumed to be dominated by a
dimension-two \VEV{A^2} condensate. In this contest a novel method for
calibrating the lattice spacing in lattice simulations is presented.Comment: 7 pages, 4 figures, XXVIII International Symposium on Lattice Field
Theory 201
Critical behavior of the compact 3d U(1) gauge theory on isotropic lattices
We report on the computation of the critical point of the deconfinement phase
transition, critical indices and the string tension in the compact three
dimensional U(1) lattice gauge theory at finite temperatures. The critical
indices govern the behavior across the deconfinement phase transition in the
pure gauge U(1) model and are generally expected to coincide with the critical
indices of the two-dimensional XY model. We studied numerically the U(1) model
for N_t=8 on lattices with spatial extension ranging from L=32 to L=256. Our
determination of the infinite volume critical point on the lattice with N_t=8
differs substantially from the pseudo-critical coupling at L=32, found earlier
in the literature and implicitly assumed as the onset value of the deconfined
phase. The critical index computed from the scaling of the
pseudo-critical couplings with the extension of the spatial lattice agrees well
with the XY value =1/2. On the other hand, the index shows large
deviation from the expected universal value. The possible reasons of such
behavior are discussed in details.Comment: 15 pages, 7 figures; version accepted for publication on J. Stat.
Mech
Critical behavior of the compact 3d U(1) theory in the limit of zero spatial coupling
Critical properties of the compact three-dimensional U(1) lattice gauge
theory are explored at finite temperatures on an asymmetric lattice. For
vanishing value of the spatial gauge coupling one obtains an effective
two-dimensional spin model which describes the interaction between Polyakov
loops. We study numerically the effective spin model for N_t=1,4,8 on lattices
with spatial extension ranging from L=64 to L=256. Our results indicate that
the finite-temperature U(1) lattice gauge theory belongs to the universality
class of the two-dimensional XY model, thus supporting the Svetitsky-Yaffe
conjecture.Comment: 17 pages, 5 figures; two references added, a few comments included,
title changed; version to appear on J. Stat. Mec
Ghost-gluon coupling, power corrections and from twisted-mass lattice QCD at Nf=2
We present results concerning the non-perturbative evaluation of the
ghost-gluon running QCD coupling constant from twisted-mass lattice
calculations. A novel method for calibrating the lattice spacing, independent
of the string tension and hadron spectrum is presented with results in
agreement with previous estimates. The value of is
computed from the running of the QCD coupling only after extrapolating to zero
dynamical quark mass and after removing a non-perturbative OPE contribution
that is assumed to be dominated by the dimension-two \VEV{A^2} gluon
condensate. The effect due to the dynamical quark mass in the determination of
\Lams is discussed.Comment: 33 pages, 6 fig
Phase transitions in strongly coupled 3d Z(N) lattice gauge theories at finite temperature
We perform an analytical and numerical study of the phase transitions in
three-dimensional Z(N) lattice gauge theories at finite temperature for N>4
exploiting equivalence of these models with a generalized version of the
two-dimensional vector Potts models in the limit of vanishing spatial coupling.
In this limit the Polyakov loops play the role of Z(N) spins. The effective
couplings of these two-dimensional spin models are calculated explicitly. It is
argued that the effective spin models have two phase transitions of BKT type.
This is confirmed by large-scale Monte Carlo simulations. Using a cluster
algorithm we locate the position of the critical points and study the critical
behavior across both phase transitions in details. In particular, we determine
various critical indices, compute the helicity modulus, the average action and
the specific heat. A scaling formula for the critical points with N is
proposed.Comment: 28 pages, 12 figures, 12 tables; version to appear on Phys. Rev.
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