2,509 research outputs found
The confined-deconfined interface tension, wetting, and the spectrum of the transfer matrix
The reduced tension of the interface between the confined and
the deconfined phase of pure gauge theory is determined from numerical
simulations of the first transfer matrix eigenvalues. At we find
for . The interfaces show universal
behavior because the deconfined-deconfined interfaces are completely wet by the
confined phase. The critical exponents of complete wetting follow from the
analytic interface solutions of a -symmetric model in three
dimensions. We find numerical evidence that the confined-deconfined interface
is rough.Comment: Talk presented at the International Conference on Lattice Field
Theory, Lattice 92, to be published in the proceedings, 4 pages, 4 figures,
figures 2,3,4 appended as postscript files, figure 1 not available as a
postscript file but identical with figure 2 of Nucl. Phys. B372 (1992) 703,
special style file espcrc2.sty required (available from hep-lat), BUTP-92/4
From Doubled Chern-Simons-Maxwell Lattice Gauge Theory to Extensions of the Toric Code
We regularize compact and non-compact Abelian Chern-Simons-Maxwell theories
on a spatial lattice using the Hamiltonian formulation. We consider a doubled
theory with gauge fields living on a lattice and its dual lattice. The Hilbert
space of the theory is a product of local Hilbert spaces, each associated with
a link and the corresponding dual link. The two electric field operators
associated with the link-pair do not commute. In the non-compact case with
gauge group , each local Hilbert space is analogous to the one of a
charged "particle" moving in the link-pair group space in a
constant "magnetic" background field. In the compact case, the link-pair group
space is a torus threaded by units of quantized "magnetic" flux,
with being the level of the Chern-Simons theory. The holonomies of the
torus give rise to two self-adjoint extension parameters, which form
two non-dynamical background lattice gauge fields that explicitly break the
manifest gauge symmetry from to . The local Hilbert space
of a link-pair then decomposes into representations of a magnetic translation
group. In the pure Chern-Simons limit of a large "photon" mass, this results in
a -symmetric variant of Kitaev's toric code, self-adjointly
extended by the two non-dynamical background lattice gauge fields. Electric
charges on the original lattice and on the dual lattice obey mutually anyonic
statistics with the statistics angle . Non-Abelian
Berry gauge fields that arise from the self-adjoint extension parameters may be
interesting in the context of quantum information processing.Comment: 38 pages, 4 figure
Quantum Link Models with Many Rishon Flavors and with Many Colors
Quantum link models are a novel formulation of gauge theories in terms of
discrete degrees of freedom. These degrees of freedom are described by quantum
operators acting in a finite-dimensional Hilbert space. We show that for
certain representations of the operator algebra, the usual Yang-Mills action is
recovered in the continuum limit. The quantum operators can be expressed as
bilinears of fermionic creation and annihilation operators called rishons.
Using the rishon representation the quantum link Hamiltonian can be expressed
entirely in terms of color-neutral operators. This allows us to study the large
N_c limit of this model. In the 't Hooft limit we find an area law for the
Wilson loop and a mass gap. Furthermore, the strong coupling expansion is a
topological expansion in which graphs with handles and boundaries are
suppressed.Comment: Lattice2001(theorydevelop), poster by O. Baer and talk by B.
Schlittgen, 6 page
A Multicanonical Algorithm and the Surface Free Energy in SU(3) Pure Gauge Theory
We present a multicanonical algorithm for the SU(3) pure gauge theory at the
deconfinement phase transition. We measure the tunneling times for lattices of
size L^3x2 for L=8,10, and 12. In contrast to the canonical algorithm the
tunneling time increases only moderately with L. Finally, we determine the
interfacial free energy applying the multicanonical algorithm.Comment: 6 pages, HLRZ-92-3
Super-Rough Glassy Phase of the Random Field XY Model in Two Dimensions
We study both analytically, using the renormalization group (RG) to two loop
order, and numerically, using an exact polynomial algorithm, the
disorder-induced glass phase of the two-dimensional XY model with quenched
random symmetry-breaking fields and without vortices. In the super-rough glassy
phase, i.e. below the critical temperature , the disorder and thermally
averaged correlation function of the phase field , behaves, for , as where and is a microscopic length scale. We
derive the RG equations up to cubic order in and predict
the universal amplitude . The
universality of results from nontrivial cancellations between
nonuniversal constants of RG equations. Using an exact polynomial algorithm on
an equivalent dimer version of the model we compute numerically and
obtain a remarkable agreement with our analytical prediction, up to .Comment: 5 pages, 3 figure
The Interface Tension in Quenched QCD at the Critical Temperature
We present results for the confinement-deconfinement interface tension
of quenched QCD. They were obtained by applying Binder's
histogram method to lattices of size for and
L=8,10,12\mbox{ and }14 with for and otherwise. The
use of a multicanonical algorithm and cylindrical geometries have turned out to
be crucial for the numerical studies.Comment: (talk presented by B. Grossmann at Lattice 92), 4 pages with 5 figure
appended as encapsulated postscript files at the end, preprint HLRZ-92-7
Magnetic properties of antiferromagnetically coupled CoFeB/Ru/CoFeB
This work reports on the thermal stability of two amorphous CoFeB layers
coupled antiferromagnetically via a thin Ru interlayer. The saturation field of
the artificial ferrimagnet which is determined by the coupling, J, is almost
independent on the annealing temperature up to more than 300 degree C. An
annealing at more than 325 degree C significantly increases the coercivity, Hc,
indicating the onset of crystallization.Comment: 4 pages, 3 figure
Disordered free fermions and the Cardy Ostlund fixed line at low temperature
Using functional RG, we reexamine the glass phase of the 2D random-field Sine
Gordon model. It is described by a line of fixed points (FP) with a
super-roughening amplitude as
temperature is varied. A speculation is that this line is identical to the
one found in disordered free-fermion models via exact results from ``nearly
conformal'' field theory. This however predicts , contradicting
numerics. We point out that this result may be related to failure of
dimensional reduction, and that a functional RG method incorporating higher
harmonics and non-analytic operators predicts a non-zero which
compares reasonably with numerics.Comment: 8 pages, 3 figures, only material adde
Lattice Fluid Dynamics from Perfect Discretizations of Continuum Flows
We use renormalization group methods to derive equations of motion for large
scale variables in fluid dynamics. The large scale variables are averages of
the underlying continuum variables over cubic volumes, and naturally live on a
lattice. The resulting lattice dynamics represents a perfect discretization of
continuum physics, i.e. grid artifacts are completely eliminated. Perfect
equations of motion are derived for static, slow flows of incompressible,
viscous fluids. For Hagen-Poiseuille flow in a channel with square cross
section the equations reduce to a perfect discretization of the Poisson
equation for the velocity field with Dirichlet boundary conditions. The perfect
large scale Poisson equation is used in a numerical simulation, and is shown to
represent the continuum flow exactly. For non-square cross sections we use a
numerical iterative procedure to derive flow equations that are approximately
perfect.Comment: 25 pages, tex., using epsfig, minor changes, refernces adde
The confined-deconfined Interface Tension and the Spectrum of the Transfer Matrix
The reduced tension of the interface between the confined and
the deconfined phase of pure gauge theory is related to the finite size
effects of the first transfer matrix eigenvalues. A lattice simulation of the
transfer matrix spectrum at the critical temperature yields
for . We found numerical evidence that
the deconfined-deconfined domain walls are completely wet by the confined
phase, and that the confined-deconfined interfaces are rough.Comment: 22 pages, LaTeX file with 4 ps figures included, HLRZ 92-47,
BUTP-92/3
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