427 research outputs found
Classical Solutions in a Lorentz-violating Maxwell-Chern-Simons Electrodynamics
We take as starting point the planar model arising from the dimensional
reduction of the Maxwell Electrodynamics with the (Lorentz-violating)
Carroll-Field-Jackiw term. We then write and study the extended Maxwell
equations and the corresponding wave equations for the potentials. The solution
to these equations show some interesting deviations from the usual MCS
Electrodynamics, with background-dependent correction terms. In the case of a
time-like background, the correction terms dominate over the MCS sector in the
region far from the origin, and establish the behaviour of a massless
Electrodynamics (in the electric sector). In the space-like case, the solutions
indicate the clear manifestation of spatial anisotropy, which is consistent
with the existence of a privileged direction is space.Comment: latex, 8 page
Neutrino flavor conversion in a neutrino background: single- versus multi-particle description
In the early Universe, or near a supernova core, neutrino flavor evolution
may be affected by coherent neutrino-neutrino scattering. We develop a
microscopic picture of this phenomenon. We show that coherent scattering does
not lead to the formation of entangled states in the neutrino ensemble and
therefore the evolution of the system can always be described by a set of
one-particle equations. We also show that the previously accepted formalism
overcounts the neutrino interaction energy; the correct one-particle evolution
equations for both active-active and active-sterile oscillations contain
additional terms. These additional terms modify the index of refraction of the
neutrino medium, but have no effect on oscillation physics.Comment: 12 pages, 3 figures, minor typos correcte
CPT, Lorentz invariance and anomalous clash of symmetries
In this paper we first discuss the analysis regarding the role of Lorentz
symmetry in the perturbative non-gravitational anomalies for a family of
fermions, which has been recently performed in arXiv:0809.0184. The theory is
assumed to be translational invariant, power-counting renormalizable and based
on a local action, but is allowed to have general Lorentz violating operators,
including those that break CPT. The main result is that Lorentz symmetry does
not participate in the clash of symmetries that leads to the anomalies.
Moreover, here we provide a simple "semiclassical" argument that shortly
illustrates the origin of this fact.Comment: 8 pages, no figures. To appear in the proceedings of Discrete '08:
Symposium on Prospects in the Physics of Discrete Symmetries, Valencia,
Spain, 11-16 Dec 200
Ward Identity for Membranes
Ward identities in the case of scattering of antisymmetric three form RR
gauge fields off a D2-brane target has been studied in type-IIA theory.Comment: 10 pages, Revtex, Version to appear in Phys.Lett.
Non-Minimal Coupling to a Lorentz-Violating Background and Topological Implications
The non-minimal coupling of fermions to a background responsible for the
breaking of Lorentz symmetry is introduced in Dirac's equation; the
non-relativistic regime is contemplated, and the Pauli's equation is used to
show how an Aharonov-Casher phase may appear as a natural consequence of the
Lorentz violation, once the particle is placed in a region where there is an
electric field. Different ways of implementing the Lorentz breaking are
presented and, in each case, we show how to relate the Aharonov-Casher phase to
the particular components of the background vector or tensor that realises the
violation of Lorentz symmetry.Comment: 8 pages, added references, no figure
Consistency analysis of a nonbirefringent Lorentz-violating planar model
In this work analyze the physical consistency of a nonbirefringent
Lorentz-violating planar model via the analysis of the pole structure of its
Feynman propagators. The nonbirefringent planar model, obtained from the
dimensional reduction of the CPT-even gauge sector of the standard model
extension, is composed of a gauge and a scalar fields, being affected by
Lorentz-violating (LIV) coefficients encoded in the symmetric tensor
. The propagator of the gauge field is explicitly evaluated
and expressed in terms of linear independent symmetric tensors, presenting only
one physical mode. The same holds for the scalar propagator. A consistency
analysis is performed based on the poles of the propagators. The isotropic
parity-even sector is stable, causal and unitary mode for .
On the other hand, the anisotropic sector is stable and unitary but in general
noncausal. Finally, it is shown that this planar model interacting with a
Higgs field supports compactlike vortex configurations.Comment: 11 pages, revtex style, final revised versio
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