262 research outputs found
Scaling Properties of the Probability Distribution of Lattice Gribov Copies
We study the problem of the Landau gauge fixing in the case of the SU(2)
lattice gauge theory. We show that the probability to find a lattice Gribov
copy increases considerably when the physical size of the lattice exceeds some
critical value , almost independent of the lattice
spacing. The impact of the choice of the copy on Green functions is presented.
We confirm that the ghost propagator depends on the choice of the copy, this
dependence decreasing for increasing volumes above the critical one. The gluon
propagator as well as the gluonic three-point functions are insensitive to
choice of the copy (within present statistical errors). Finally we show that
gauge copies which have the same value of the minimisation functional () are equivalent, up to a global gauge transformation, and
yield the same Green functions.Comment: replaced with revised version; 23 pages, 7 figures, 27 table
New bounds on neutrino magnetic moment and re-examination of plasma effect in neutrino spin light
Recent discussion on the possibility to obtain more stringent bounds on
neutrino magnetic moment has stimulated new interest to possible effects
induced by neutrino magnetic moment. In particular, in this note after a short
review on neutrino magnetic moment we re-examine the effect of plasmon mass on
neutrino spin light radiation in dense matter. We track the entry of the
plasmon mass quantity in process characteristics and found out that the most
substantial role it plays is the formation of the process threshold. It is
shown that far from this point the plasmon mass can be omitted in all the
corresponding physical quantities and one can rely on the results of massless
photon spin light radiation theory in matter.Comment: to appear in Nuovo Cimento 35 C, No. 1, 2012 (based on the talk
presented at the 25th Rencontres de Physique de la Vallee d'Aoste on "Results
and Perspectives in Particle Physics", La Thuile, February 27 - March 5, 201
Non-Perturbative Approach to the Landau Gauge Gluodynamics
We discuss a non-perturbative lattice calculation of the ghost and gluon
propagators in the pure Yang-Mills theory in Landau gauge. The ultraviolet
behaviour is checked up to NNNLO yielding the value
\Lambda^{n_f=0}_{\ms}=269(5)^{+12}_{-9}\text{MeV}, and we show that lattice
Green functions satisfy the complete Schwinger-Dyson equation for the ghost
propagator for all considered momenta. The study of the above propagators at
small momenta showed that the infrared divergence of the ghost propagator is
enhanced, whereas the gluon propagator seem to remain finite and non-zero. The
result for the ghost propagator is consistent with the analysis of the
Slavnov-Taylor identity, whereas, according to this analysis, the gluon
propagator should diverge in the infrared, a result at odds with other
approaches.Comment: To appear in the proceedings of the workshop "Hadron Structure and
QCD: from LOW to HIGH energies" (St. Petersburg, Russia, 20-24 September
2005
Asymptotic behavior of the ghost propagator in SU3 lattice gauge theory
We study the asymptotic behavior of the ghost propagator in the quenched
SU(3) lattice gauge theory with Wilson action. The study is performed on
lattices with a physical volume fixed around 1.6 fm and different lattice
spacings: 0.100 fm, 0.070 fm and 0.055 fm. We implement an efficient algorithm
for computing the Faddeev-Popov operator on the lattice. We are able to
extrapolate the lattice data for the ghost propagator towards the continuum and
to show that the extrapolated data on each lattice can be described up to
four-loop perturbation theory from 2.0 GeV to 6.0 GeV. The three-loop values
are consistent with those extracted from previous perturbative studies of the
gluon propagator. However the effective \Lambda_{\ms} scale which reproduces
the data does depend strongly upon the order of perturbation theory and on the
renormalization scheme used in the parametrization. We show how the truncation
of the perturbative series can account for the magnitude of the dependency in
this energy range. The contribution of non-perturbative corrections will be
discussed elsewhere.Comment: 26 pages, 7 figure
- …