43,779 research outputs found
Gribov ambiguities at the Landau -- maximal Abelian interpolating gauge
In a previous work, we presented a new method to account for the Gribov
ambiguities in non-Abelian gauge theories. The method consists on the
introduction of an extra constraint which directly eliminates the infinitesimal
Gribov copies without the usual geometric approach. Such strategy allows to
treat gauges with non-hermitian Faddeev-Popov operator. In this work, we apply
this method to a gauge which interpolates among the Landau and maximal Abelian
gauges. The result is a local and power counting renormalizable action, free of
infinitesimal Gribov copies. Moreover, the interpolating tree-level gluon
propagator is derived.Comment: Several changes: figures removed, typos corrected and discussions
included. 24 pages, to appear in EPJ
On the elimination of infinitesimal Gribov ambiguities in non-Abelian gauge theories
An alternative method to account for the Gribov ambiguities in gauge theories
is presented. It is shown that, to eliminate Gribov ambiguities, at
infinitesimal level, it is required to break the BRST symmetry in a soft
manner. This can be done by introducing a suitable extra constraint that
eliminates the infinitesimal Gribov copies. It is shown that the present
approach is consistent with the well established known cases in the literature,
i.e., the Landau and maximal Abelian gauges. The method is valid for gauges
depending exclusively on the gauge field and is restricted to classical level.
However, occasionally, we deal with quantum aspects of the technique, which are
used to improve the results.Comment: 29 pp. No figures. Discussions added. Final version to appear in EPJ
Inner and outer edge states in graphene rings: A numerical investigation
We numerically investigate quantum rings in graphene and find that their
electronic properties may be strongly influenced by the geometry, the edge
symmetries and the structure of the corners. Energy spectra are calculated for
different geometries (triangular, hexagonal and rhombus-shaped graphene rings)
and edge terminations (zigzag, armchair, as well as the disordered edge of a
round geometry). The states localized at the inner edges of the graphene rings
describe different evolution as a function of magnetic field when compared to
those localized at the outer edges. We show that these different evolutions are
the reason for the formation of sub-bands of edge states energy levels,
separated by gaps (anticrossings). It is evident from mapping the charge
densities that the anticrossings occur due to the coupling between inner and
outer edge states.Comment: 8 pages, 7 figures. Figures in low resolution due to size
requirements - higher quality figures on reques
A non-perturbative study of matter field propagators in Euclidean Yang-Mills theory in linear covariant, Curci-Ferrari and maximal Abelian gauges
In this work, we study the propagators of matter fields within the framework
of the Refined Gribov-Zwanziger theory, which takes into account the effects of
the Gribov copies in the gauge-fixing quantization procedure of Yang-Mills
theory. In full analogy with the pure gluon sector of the Refined
Gribov-Zwanziger action, a non-local long-range term in the inverse of the
Faddeev-Popov operator is added in the matter sector. Making use of the recent
BRST invariant formulation of the Gribov-Zwanziger framework achieved in [Capri
et al 2016], the propagators of scalar and quark fields in the adjoint and
fundamental representations of the gauge group are worked out explicitly in the
linear covariant, Curci-Ferrari and maximal Abelian gauges. Whenever lattice
data are available, our results exhibit good qualitative agreement.Comment: 27 pages, no figures; V2, minor modifications, to appear in EPJ
Space-time Torsion and Neutrino Oscillations in Vacuum
The objective of this study is to verify the consistency of the prescription
of alternative minimum coupling (connection) proposed by the Teleparallel
Equivalent to General Relativity (TEGR) for the Dirac equation. With this aim,
we studied the problem of neutrino oscillations in Weitzenbock space-time in
the Schwarzschild metric. In particular, we calculate the phase dynamics of
neutrinos. The relation of spin of the neutrino with the space-time torsion is
clarified through the determination of the phase differences between spin
eigenstates of the neutrinos.Comment: 07 pages, no figure
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