506 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
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