871 research outputs found
Perturbative contributions to Wilson loops in twisted lattice boxes and reduced models
We compute the perturbative expression of Wilson loops up to order for
SU() lattice gauge theories with Wilson action on a finite box with twisted
boundary conditions. Our formulas are valid for any dimension and any
irreducible twist. They contain as a special case that of the 4-dimensional
Twisted Eguchi-Kawai model for a symmetric twist with flux . Our results
allow us to analyze the finite volume corrections as a function of the flux. In
particular, one can quantify the approach to volume independence at large
as a function of flux . The contribution of fermion fields in the adjoint
representation is also analyzed.Comment: pdflatex 57 pages, 9 figures, 4 appendice
Topology by improved cooling: susceptibility and size distributions
We use a cooling algorithm based on an improved action with scale invariant
instanton solutions, which needs no monitoring or calibration and has a
inherent cut off for dislocations. We present results for SU(2) Yang-Mills
theory where the method provides good susceptibility data and physical size
distributions of instantons.Comment: 3 pages, 4 figures. Talk presented at LATTICE96(topology
Improved cooling algorithm for gauge theories
We propose and study a ``gold-washing" - type of algorithm which smooths out
the short range fluctuations but leaves invariant instantons above a certain
size. The algorithm needs no monitoring or calibration.Comment: Latex file, 4 pages, 4 figures in uuencoded compressed tar file.
Contribution to Lattice 9
The twisted gradient flow running coupling
We measure the running of the 't Hooft coupling by performing a
step scaling analysis of the Twisted Eguchi-Kawai (TEK) model, the SU()
gauge theory on a single site lattice with twisted boundary conditions. The
computation relies on the conjecture that finite volume effects for SU(N) gauge
theories defined on a 4-dimensional twisted torus are controlled by an
effective size parameter , with the torus period. We
set the scale for the running coupling in terms of and use the
gradient flow to define a renormalized 't Hooft coupling .
In the TEK model, this idea allows the determination of the running of the
coupling through a step scaling procedure that uses the rank of the group as a
size parameter. The continuum renormalized coupling constant is extracted in
the zero lattice spacing limit, which in the TEK model corresponds to the large
limit taken at fixed value of . The coupling constant is
thus expected to coincide with that of the ordinary pure gauge theory at . The idea is shown to work and permits us to follow the evolution of
the coupling over a wide range of scales. At weak coupling we find a remarkable
agreement with the perturbative two-loop formula for the running coupling.Comment: 22 pages, 7 figure
Mass anomalous dimension of Adjoint QCD at large N from twisted volume reduction
In this work we consider the gauge theory with two Dirac fermions in
the adjoint representation, in the limit of large . In this limit the
infinite-volume physics of this model can be studied by means of the
corresponding twisted reduced model defined on a single site lattice. Making
use of this strategy we study the reduced model for various values of up to
289. By analyzing the eigenvalue distribution of the adjoint Dirac operator we
test the conformality of the theory and extract the corresponding mass
anomalous dimension.Comment: 17 pages, 11 figures. Version to appear in JHEP - corrected typos and
reference
`t Hooft model on the Lattice
Lattice results are presented for the meson spectrum of 1+1 dimensional gauge
theory at large , using the Twisted Eguchi-Kawai model. Comparison is made
to the results obtained by `t Hooft in the light cone gauge.Comment: pdflatex 7 page
Glueball masses in 2+1 dimensional SU(N) gauge theories with twisted boundary conditions
We analyze 2+1 dimensional Yang-Mills theory regularized on a lattice with
twisted boundary conditions in the spatial directions. In previous work it was
shown that the observables in the non-zero electric flux sectors obey the
so-called -scaling, i.e. depend only on the dimensionless variable and the angle given by the parameters of the twist (
being the length of the spatial torus and the inverse 't Hooft coupling).
It is conjectured that this scaling is obeyed by all physical quantities. In
this work we extend the previous analyses to the zero electric flux (glueball)
sector. We study the mass of the lightest scalar glueball in two theories with
different but matching and in a wide range of couplings
from the perturbative small-volume regime to the non-perturbative one. We find
that the results are consistent with the -scaling hypothesis.Comment: 7 pages, contribution to the 32nd International Symposium on Lattice
Field Theory, 23-28 June, 2014. Columbia University New York, NY; v2:
references added, minor changes; PoS(LATTICE2014)05
Cooling, Physical Scales and the Vacuum Structure of Y-M Theories
We present a cooling method controlled by a physical cooling radius that
defines a scale below which fluctuations are smoothed out while leaving physics
unchanged at all larger scales. This method can be generally used as a gauge
invariant low pass filter to extract the physics from noisy MC configurations.
Here we apply this method to study topological properties of lattice gauge
theories where it allows to retain instanton--anti-instanton pairs.Comment: Lattice'99 contribution, 3 pages, 5 figure
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