4 research outputs found
Nonperturbative QCD vacuum and Colour Superconductivity
We discuss the possibility of existence of colour superconducting state in
real QCD vacuum with nonzero gluon condensate. We argue, that nonperturbative
gluonic fields might play a crucial role in colour superconductivity scenario.Comment: LaTeX, 12 pages, reference adde
A lattice study of 3D compact QED at finite temperature
We study the deconfinement phase transition and monopole properties in the
finite temperature 3D compact Abelian gauge model on the lattice. We predict
the critical coupling as function of the lattice size in a simplified model to
describe monopole binding. We demonstrate numerically that the monopoles are
sensitive to the transition. In the deconfinement phase the monopoles appear in
the form of a dilute gas of magnetic dipoles. In the confinement phase both
monopole density and string tension differ from semiclassical estimates if
monopole binding is neglected. However, the analysis of the monopole clusters
shows that the relation between the string tension and the density of monopoles
in charged clusters is in reasonable agreement with those predictions. We study
the cluster structure of the vacuum in both phases of the model.Comment: 18 pages, 14 EPS figures, LaTeX uses epsfig.st
The photon propagator in compact QED_{2+1}: the effect of wrapping Dirac strings
We discuss the influence of closed Dirac strings on the photon propagator in
the Landau gauge emerging from a study of the compact U(1) gauge model in 2+1
dimensions. This gauge also minimizes the total length of the Dirac strings.
Closed Dirac strings are stable against local gauge-fixing algorithms only due
to the torus boundary conditions of the lattice. We demonstrate that these
left-over Dirac strings are responsible for the previously observed unphysical
behavior of the propagator of space-like photons (D_T) in the deconfinement
(high temperature) phase. We show how one can monitor the number N_3 of thermal
Dirac strings which allows to separate the propagator measurements into N_3
sectors. The propagator in N_3 \neq 0 sectors is characterized by a non--zero
mass and an anomalous dimension similarly to the confinement phase. Both mass
squared and anomalous dimension are found to be proportional to N_3.
Consequently, in the N_3=0 sector the unphysical behavior of the D_T photon
propagator is cured and the deviation from the free massless propagator
disappears.Comment: 13 pages, 13 figures, 1 tabl
Modelling the QCD Phase Transition with an Effective Lagrangian of Light and Massive Hadrons
The temperature dependence of quark and gluon condensates in QCD as precursor
of the chiral and deconfining phase transition is modelled with a conformally
extended non-linear sigma-model including broken chiral and scale invariance.
The model is further enlarged by including (free) heavier hadrons. Within this
frame we then study the interplay of QCD scale breaking effects and heavier
hadrons in chiral symmetry restoration.Comment: 23 pages, LaTeX, 5 figures, uses epsfig.st