R. Casana

New

In this work, we propose a CPT-even and Lorentz-violating dimension-five nonminimal coupling between fermionic and gauge fields, involving the CTP-even and Lorentz-violating gauge tensor of the SME. This nonminimal coupling modifies the Dirac equation, whose nonrelativistic regime is governed by a Hamiltonian which induces new effects, such as an electric-Zeeman-like spectrum splitting and an anomalous-like contribution to the electron magnetic moment, between others. Some of these new effects allows to constrain the magnitude of this nonminimal coupling in 1 part in 10^16.

CPT

The CPT-even gauge sector of the standard model extension is composed of 19 components comprised in the tensor (K{sub F}){sub {mu}{nu}{rho}{sigma}}, of which nine do not yield birefringence. In this work, we examine the Maxwell electrodynamics supplemented by these nine nonbirefringent CPT-even components in aspects related to the Feynman propagator and full consistency (stability, causality, unitarity). We adopt a prescription that parametrizes the nonbirefringent components in terms of a symmetric and traceless tensor, K{sub {mu}{nu}}, and second parametrization that writes K{sub {mu}{nu}} in terms of two arbitrary four-vectors, U{sub {mu}} and V{sub {nu}}. We then explicitly evaluate the gauge propagator of this electrodynamics in a tensor closed way. In the sequel, we show that this propagator and involved dispersion relations can be specialized for the parity-odd and parity-even sectors of the tensor (K{sub F}){sub {mu}{nu}{rho}{sigma}}. In this way, we reassess some results of the literature and derive some new outcomes showing that the parity-even anisotropic sector engenders a stable, noncausal and unitary electrodynamics.

-even and Lorentz-violating nonminimal coupling in the Dirac equation

In this work, we explicitly evaluate the gauge propagator of the Maxwell theory supplemented by the CPT-even term of the standard model extension. First, we specialize our evaluation for the parity-odd sector of the tensor W{sub {mu}}{sub {nu}}{sub {rho}}{sub {sigma}}, using a parametrization that retains only the three nonbirefringent coefficients. From the poles of the propagator, it is shown that physical modes of this electrodynamics are stable, noncausal and unitary. In the sequel, we carry out the parity-even gauge propagator using a parametrization that allows to work with only the isotropic nonbirefringent element. In this case, we show that the physical modes of the parity-even sector of the tensor W are causal, stable and unitary for a limited range of the isotropic coefficient.

Feynman propagator for the nonbirefringent CPT-even electrodynamics of the standard model extension

Abstract In this Letter we show for the first time that the usual CPT-even gauge term of the Standard Model Extension (SME), in its full structure, can be radiatively generated, in a gauge invariant level, in the context of a modified QED endowed with a dimension-five nonminimal coupling term recently proposed in the literature. As a consequence, the existing upper bounds on the coefficients of the tensor ( K F ) can be used to improve the bounds on the magnitude of the nonminimal coupling, λ ( K σ F ) , by the factors 105 or 1025. The nonminimal coupling also generates higher-order derivative contributions to the gauge field effective action quadratic terms.

Gauge propagator and physical consistency of the CPT-even part of the Standard Model Extension

We propose a new \emph{CPT}-even and Lorentz-violating nonminimal coupling between fermions and Abelian gauge fields involving the CPT-even tensor

Radiative generation of the CPT-even gauge term of the SME from a dimension-five nonminimal coupling term

(K_{F})_{\mu\nu\alpha\beta}

Effects of a CPT-even and Lorentz-violating nonminimal coupling on the electron-positron scattering

of the standard model extension. We thus investigate its effects on the cross section of the electron-positron scattering by analyzing the process

Finite temperature behavior of the CPT-even and parity-even electrodynamics of the standard model extension

e^{+}+e^{-}\rightarrow\mu^{+}+\mu^{-}

Classical solutions for the Lorentz-violating and CPT-even term of the Standard Model Extension

. Such a study was performed for the parity-odd and parity-even nonbirefringent components of the Lorentz-violating

Generalized self-dual Maxwell-Chern-Simons-Higgs model

(K_{F})_{\mu\nu\alpha\beta}