44,180 research outputs found
A model for structural defects in nanomagnets
A model for describing structural pointlike defects in nanoscaled
ferromagnetic materials is presented. Its details are explicitly developed
whenever interacting with a vortex-like state comprised in a thin nanodisk.
Among others, our model yields results for the vortex equilibrium position
under the influence of several defects along with an external magnetic field in
good qualitative agreement with experiments. We also discuss how such defects
may affect the vortex motion, like its gyrotropic oscillation and dynamical
polarization reversal.Comment: 8 pages, resubmitted to Journal of Applied Physic
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
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