288 research outputs found
The lattice ghost propagator in Landau gauge up to three loops using Numerical Stochastic Perturbation Theory
We complete our high-accuracy studies of the lattice ghost propagator in
Landau gauge in Numerical Stochastic Perturbation Theory up to three loops. We
present a systematic strategy which allows to extract with sufficient precision
the non-logarithmic parts of logarithmically divergent quantities as a function
of the propagator momentum squared in the infinite-volume and limits.
We find accurate coincidence with the one-loop result for the ghost self-energy
known from standard Lattice Perturbation Theory and improve our previous
estimate for the two-loop constant contribution to the ghost self-energy in
Landau gauge. Our results for the perturbative ghost propagator are compared
with Monte Carlo measurements of the ghost propagator performed by the Berlin
Humboldt university group which has used the exponential relation between
potentials and gauge links.Comment: 8 pages, 6 figures, XXVII International Symposium on Lattice Field
Theory - LAT2009, Beijin
The SU(3) Beta Function from Numerical Stochastic Perturbation Theory
The SU(3) beta function is computed from Wilson loops to 20th order numerical
stochastic perturbation theory. An attempt is made to include massless
fermions, whose contribution is known analytically to 4th order. The question
whether the theory admits an infrared stable fixed point is addressed.Comment: 10 pages, 7 figures, version to be published in Physics Letters
Two-point functions of quenched lattice QCD in Numerical Stochastic Perturbation Theory. (I) The ghost propagator in Landau gauge
This is the first of a series of two papers on the perturbative computation
of the ghost and gluon propagators in SU(3) Lattice Gauge Theory. Our final aim
is to eventually compare with results from lattice simulations in order to
enlight the genuinely non-perturbative content of the latter. By means of
Numerical Stochastic Perturbation Theory we compute the ghost propagator in
Landau gauge up to three loops. We present results in the infinite volume and
limits, based on a general strategy that we discuss in detail.Comment: 27 pages, 11 figure
Two-point functions of quenched lattice QCD in Numerical Stochastic Perturbation Theory
We summarize the higher-loop perturbative computation of the ghost and gluon
propagators in SU(3) Lattice Gauge Theory. Our final aim is to compare with
results from lattice simulations in order to expose the genuinely
non-perturbative content of the latter. By means of Numerical Stochastic
Perturbation Theory we compute the ghost and gluon propagators in Landau gauge
up to three and four loops. We present results in the infinite volume and limits, based on a general fitting strategy.Comment: 3 pages, 5 figures, talk at conference QCHS-IX, Madrid 201
Perturbative renormalisation of quark bilinear operators for overlap fermions with and without stout links and improved gauge action
We calculate lattice renormalisation constants of local and one-link quark
operators for overlap fermions and improved gauge actions in one-loop
perturbation theory. For the local operators we stout smear the SU(3) links in
the fermionic action. Using the popular tadpole improved L\"uscher-Weisz
actions at and we present numerical values for the Z
factors in the scheme (partly as function of the stout smearing
strength). We compare various levels of mean field (tadpole) improvement which
have been applied to our results.Comment: 7 page
- …