Investigações no cenário da QED estendida CPT-par com acoplamento mínimo e não mínimo

Abstract

In this report, we investigated aspects of an extended quantum electrodynamics (QED) which incorporates Lorentz-violation in its structure. Among the many models describing such Lorentz-violating field theories, we highlight the standard model extension (SME). An alternative approach to introduce Lorentz violation is through the use of a non-minimal coupling which includes new interaction terms, mostly represented by dimension-five operators or higher. In this context, we have proposed a new non-minimal coupling introduced in the covariant derivative Dµ = ∂µ +ieAµ + λ 2 (KσF )µναβ γ νF αβ. The term (KσF )µναβ γ νF αβ which is CPT-even. This covariant derivative modifies the Dirac equation, making possible to investigate its effects for example, in non-relativistic limit, where it yields new effects allowing to impose restrictive upper-bounds on the magnitude of Lorentz violating parameters (LV). A second application was to investigate such effects on the scattering amplitudes in QED environment. Such effects are analyzed by implementing an additional Feynman rule × → iλVβ = λ(KσF )µναβσ µνq α ,besides the usual • → −ieγµ . As an example, we consider the scattering e + + e − → µ + + µ − in ultra-relativistic limit. The obtained cross section and the experimental data, allow to determine an upper-bound on the magnitude of the LV coefficients. The following study, still within the nonminimal coupling context, we consider quantum corrections produced by it in the photon sector, i.e., we compute the vacuum polarization tensor. It is shown that a term type (KF )µναβ F µνF αβ (the well-known CPT-even abelian gauge term) of the SME electrodynamics is generated radiatively at 1-loop order. Other important aspect of SME electrodynamics is consider its covariant quantization. This way, we focus on the anisotropic parity-even term κ µν belonging to the CPT-even and parity-even sector. The quantization of this model becomes problematic in the Lorenz gauge, however, the implementation of a modified Lorenz condition (g µν + κ µν) ∂µAν leads to a successful implementation of the Gupta Bleuler quantization.