163 research outputs found
Gauge potential singularities and the gluon condensate at finite temperatures
The continuum limit of SU(2) lattice gauge theory is carefully investigated
at zero and at finite temperatures. It is found that the continuum gauge field
has singularities originating from center degrees of freedom being discovered
in Landau gauge. Our numerical results show that the density of these
singularities properly extrapolates to a non-vanishing continuum limit. The
action density of the non-trivial Z_2 links is tentatively identified with the
gluon condensate. We find for temperatures larger than the deconfinement
temperature that the thermal fluctuations of the embedded Z_2 gauge theory
result in an increase of the gluon condensate with increasing temperature.Comment: 3 pages, 2 figures, talk presented by K. Langfeld at the 19th
International Symposium on Lattice Field Theory (LATTICE2001), Berlin,
19.-24.8.2001, to appear in the proceeding
The canon in art history: concepts and approaches
Although the canon has recently been increasingly the focus of art-historical research, there does not seem to be clarity, much less agreement, on how such research should be conducted. Art historians have taken various positions on the subject. This article intends to explain the main positions that dominate literature on the canon and canon formation, the theoretical and methodological starting points that provide the framework for such research, as well as to propose that social art history offers a more comprehensive approach that might overcome the strict separation between these positions
Correlations of center flux in SU(2) Yang-Mills theory
By using the method of center projection the center vortex part of the gauge
field is isolated and its propagator is evaluated in the center Landau gauge,
which minimizes the open 3-dimensional Dirac volumes of non-trivial center
links bounded by the closed 2-dimensional center vortex surfaces. The center
field propagator is found to dominate the gluon propagator (in Landau gauge) in
the low momentum regime and to give rise to an OPE correction to the latter of
.The screening mass of the center vortex field vanishes
above the critical temperature of the deconfinement phase transition, which
naturally explains the second order nature of this transition consistently with
the vortex picture. Finally, the ghost propagator of maximal center gauge is
found to be infrared finite and thus shows no signal of confinement.Comment: Presented at 23rd International Symposium on Lattice Field Field:
Lattice 2005, Trinity College, Dublin, Ireland, 25-30 Jul 200
Vortex critical behavior at the de-confinement phase transition
The de-confinement phase transition in SU(2) Yang-Mills theory is revisited
in the vortex picture. Defining the world sheets of the confining vortices by
maximal center projection, the percolation properties of the vortex lines in
the hypercube consisting of the time axis and two spatial axis are studied.
Using the percolation cumulant, the temperature for the percolation transition
is seen to be in good agreement with the critical temperature of the thermal
transition. The finite size scaling function for the cumulant is obtained. The
critical index of the finite size scaling function is consistent with the index
of the 3D Ising model.Comment: 4 pages, 4 PS figures, using revtex4, paragraph and refs added, typo
correcte
Monopoles contra vortices in SU(2) lattice gauge theory?
We show that the scenario of vortex induced confinement of center--projected
SU(2) lattice gauge theory is not necessarily in conflict with the findings in
the positive plaquette model.Comment: 3 pages, LaTeX, comment to be published in Phys. Rev.
Status of center dominance in various center gauges
We review arguments for center dominance in center gauges where vortex
locations are correctly identified. We introduce an appealing interpretation of
the maximal center gauge, discuss problems with Gribov copies, and a cure to
the problems through the direct Laplacian center gauge. We study correlations
between direct and indirect Laplacian center gauges.Comment: Presented by S. Olejnik at the NATO Advanced Research Workshop
"Confinement, Topology, and other Non-Perturbative Aspects of QCD", Jan.
21-27, 2002, Stara Lesna, Slovakia. 10 pages, 3 figures (8 EPS files), uses
crckapb.st
Remarks on the Gribov Problem in Direct Maximal Center Gauge
We review the equivalence of maximal center gauge fixing to the problem of
finding the best fit, to a given lattice gauge field, by a thin vortex
configuration. This fit is necessarily worst at the location of P-plaquettes.
We then compare the fits achieved in Gribov copies generated by (i)
over-relaxation; (ii) over-relaxation after Landau gauge preconditioning; and
(iii) simulated annealing. Simulated annealing yields the best fit if all links
on the lattice are included, but the situation changes if we consider only the
lattice volume exterior to P-plaquettes. In this exterior region, the fit is
best for Gribov copies generated by over-relaxation, and worst for Gribov
copies generated after Landau gauge preconditioning. The two fitting criteria
(including or not including the P-plaquettes) yield string tensions differing
by -34% to +20% respectively, relative to the full string tension. Our usual
procedure (``quenched minimization'') seems to be a compromise between these
criteria, and yields string tensions at an intermediate value close to the full
string tension.Comment: 14 pages, 6 figure
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