1,150 research outputs found
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
Deconfinement in QCD with dynamical quarks
We study the phase structure of full QCD within the canonical ensemble with
respect to triality in a lattice formulation. The procedure for the calculation
of the effective potentials in this case is given. As an example we consider
the three dimensional SU(2) gauge model at finite temperatures in the strong
coupling region. The potential exhibits a deconfinement phase transition unlike
the similar potential obtained in the grand canonical ensemble which
demonstrates explicit Z(N) symmetry breaking at any temperature. Furthermore,
we investigate the effective potential with the chiral condensate included. In
contradiction to other authors, we find chiral symmetry restoration in all
triality sectors. In the scheme with massless staggered fermions we observe
chiral symmetry restoration accompanying a deconfinement phase transition of
first order. Above the critical point, besides two Z(2) symmetric "deconfining"
vacua there exists a metastable "confining" vacuum in a wide region of
parameters. Such a picture could be interpreted as an indication on a mixed
state of hadrons and quarks in the vicinity of the critical line.Comment: 17 pages with 6 eps. figures include
Fresh look on triality
Investigating the symmetry in Quantum Chromodynamics (QCD) we show that
full QCD with a vacuum of vanishing baryonic number does not lead to metastable
phases. Rather in QCD with dynamical fermions, the degeneracy of phases
manifests itself in observables without open triality.Comment: 9 pages, 0 figures, latex, IK-TUW-Preprint 930840
Mass Gap, Abelian Dominance and Vortex Dynamics in SU(2) Spin Model
We discuss a new approach to the investigation of the nature of the mass gap
in spin systems with continuous global symmetries which is much analogous to
the method of abelian projection in the gauge theories. We suggest that the
abelian degrees of freedom, in particular, abelian vortices are responsible for
the mass gap generation phenomena in the non-abelian spin systems. To check our
hypothesis we study numerically the three-dimensional SU(2) spin model in the
Maximal Abelian projection. We find that the abelian mass gap in the projected
theory coincides with the full non-abelian mass gap within numerical errors.
The study of the percolation properties of the abelian vortex trajectories
shows that the phase transition and the mass gap generation in the 3D SU(2)
spin model are driven by the abelian vortex condensation.Comment: 12 pages, LaTeX, 4 figures, uses epsf.sty; Fig.3 is replaced and a
few comments are adde
Phase structure and confinement properties of noncompact gauge theories I
In the context of reviewing noncompact lattice gauge models at zero and
finite temperature we study in detail a contribution of the invariant measure
and the time-like plaquette configurations to correlation functions, analyze
the problem of the compactness of the potentials in respect to the confinement
and indicate the essential features to deal with the Wilson gauge theory in the
weak coupling region. A method for calculating an effective confining
noncompact model is also proposed.Comment: Latex file, 24 pages, no figure
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
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