344 research outputs found
A remark on the BRST symmetry in the Gribov-Zwanziger theory
We show that the soft breaking of the BRST symmetry arising in the
Gribov-Zwanziger theory can be converted into a linear breaking upon
introduction of a set of BRST quartets of auxiliary fields. Due to its
compatibility with the Quantum Action Principle, the linearly broken BRST
symmetry can be directly converted into a suitable set of useful Slavnov-Taylor
identities. As a consequence, it turns out that the renormalization aspects of
the Gribov-Zwanziger theory can be addressed by means of the cohomology of a
nilpotent local operatorComment: 11 pages, final version to appear in Phys. Rev.
Off-diagonal mass generation for Yang-Mills theories in the maximal Abelian gauge
We investigate a dynamical mass generation mechanism for the off-diagonal
gluons and ghosts in SU(N) Yang-Mills theories, quantized in the maximal
Abelian gauge. Such a mass can be seen as evidence for the Abelian dominance in
that gauge. It originates from the condensation of a mixed gluon-ghost operator
of mass dimension two, which lowers the vacuum energy. We construct an
effective potential for this operator by a combined use of the local composite
operators technique with algebraic renormalization and we discuss the gauge
parameter independence of the results. We also show that it is possible to
connect the vacuum energy, due to the mass dimension two condensate discussed
here, with the non-trivial vacuum energy originating from the condensate ,
which has attracted much attention in the Landau gauge.Comment: 15 pages. Revtex. 1 .eps figure. Talk given by D.Dudal at XXV
Encontro Nacional de Fisica de Particulas e Campos, Caxambu, Minas Gerais,
Brasil, 24-28 Aug 2004. To appear in Brazilian Journal of Physic
Renormalizability of the linearly broken formulation of the BRST symmetry in presence of the Gribov horizon in Landau gauge Euclidean Yang-Mills theories
In previous work arXiv:1009.4135 we have shown that the soft breaking of the
BRST symmetry arising within the Gribov-Zwanziger framework can be converted
into a linear breaking, while preserving the nilpotency of the BRST operator.
Due to its compatibility with the Quantum Action Principle, the linearly broken
BRST symmetry directly translates into a set of Slavnov-Taylor identities. We
show that these identities guarantee the multiplicative renormalizability of
both Gribov-Zwanziger and Refined Gribov-Zwanziger theories to all orders. The
known property that only two renormalization factors are needed is recovered.
The non-renormalization theorem of the gluon-ghost-antighost vertex as well as
the renormalization factor of the Gribov parameter are derived within the
linearly broken formulation.Comment: 20 pages, references added, version accepted for publication in
Physical Review
Renormalization group aspects of the local composite operator method
We review the current status of the application of the local composite
operator technique to the condensation of dimension two operators in quantum
chromodynamics (QCD). We pay particular attention to the renormalization group
aspects of the formalism and the renormalization of QCD in various gauges.Comment: 13 latex pages, talk presented at RG0
Study of the Gribov region in Euclidean Yang-Mills theories in the maximal Abelian gauge
The properties of the Gribov region in SU(2) Euclidean Yang-Mills theories in
the maximal Abelian gauge are investigated. This region turns out to be bounded
in all off-diagonal directions, while it is unbounded along the diagonal one.
The soft breaking of the BRST invariance due to the restriction of the domain
of integration in the path integral to the Gribov region is scrutinized. Owing
to the unboundedness in the diagonal direction, the invariance with respect to
Abelian transformations is preserved, a property which is at the origin of the
local U(1) Ward identity of the maximal Abelian gauge.Comment: 15 pages, one reference added, version accepted for publication in
Phys. Rev.
Vacuum Condensates and Dynamical Mass Generation in Euclidean Yang-Mills Theories
Vacuum condensates of dimension two and their relevance for the dynamical
mass generation for gluons in Yang-Mills theories are discussedComment: Talk given at the International Conference on Color Confinement and
Hadrons in Quantum Chromodynamics, Confinement 2003, TITech and RIKEN, Tokyo,
Japan, July 21-24, 200
The infrared behavior of the gluon and ghost propagators in SU(2) Yang-Mills theory in the maximal Abelian gauge
We report on some recent analytical results on the behaviour of the gluon and
ghost propagators in Euclidean SU(2) Yang-Mills theory quantized in the maximal
Abelian gauge (MAG). This gauge is of particular interest for the dual
superconductivity picture to explain color confinement. Two kinds of effects
are taken into account: those arising from a treatment of Gribov copies in the
MAG and those arising from a dynamical mass originating in a dimension two
gluon condensate. The diagonal component of the gluon propagator displays the
typical Gribov-type behaviour, while the off-diagonal component is of the
Yukawa type due to the dynamical mass. These results are in qualitative
agreement with available lattice data on the gluon propagators. The
off-diagonal ghost propagator exhibits an infrared enhancement due to the
Gribov restriction, while the diagonal one remains unaffected.Comment: 6 pages. Talk given by S.P. Sorella at the "I Latin American Workshop
on High Energy Phenomenology (I LAWHEP)", December 1-3 2005, Instituto de
Fisica, UFRGS, Porto Alegre, Rio Grande Do Sul, Brasi
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