Unitarity and non-relativistic potential energy in a higher-order Lorentz symmetry breaking electromagnetic model

The Lorentz-violating model proposed by Myers and Pospelov suffers from a higher-derivative pathology due to a dimension-5 operator. In particular, its electromagnetic sector exhibits an spectrum which contains, in addition to an expected massless photon, ghost contributions that could (in principle) spoil the unitarity of the model. We find that unitarity at tree-level can be assured for pure spacelike, timelike and lightlike background four-vectors (the last two under restrictions upon the allowed momenta). We then analyze the non-relativistic interparticle potential energy behavior for different background four-vectors and compare to the usual Coulomb potential.Comment: Accepted for publication in Physical Review

Magnetic monopoles in Lorentz-violating electrodynamics

We investigate the possibility of coexistence between Dirac-like monopoles and Lorentz-violating electrodynamics. For this purpose, we study three distinct models: Myers-Pospelov, Ellis et al. and Gambini-Pullin. In particular, we find that in the Myers-Pospelov electrodynamics, magnetic sources may be properly induced when it is accompanied by the appearance of an extra electric current. The symmetry under duality transformations and the Dirac quantization condition in the aforementioned theories is also discussed.Comment: 6 page

Photon Mass and Very Long Baseline Interferometry

A relation between the photon mass, its frequency, $\nu$, and the deflection parameter, $\gamma$, determined by experimentalists (which characterizes the contribution of space curvature to gravitational deflection) is found. This amazing result allows us to conclude that the knowledge of the parameters $\nu$ and $\gamma$ is all we need to set up gravitational bounds on the photon mass. By considering as inputs the most recent measurements of the solar gravitational deflection of radio waves obtained via the Very Long Baseline Interferometry, upper bounds on the photon mass are estimated.Comment: Accepted for publication in International Journal of Modern Physics

Some interesting features of new massive gravity

A proof that new massive gravity - the massive 3D gravity model proposed by Bergshoeff, Hohm and Townsend (BHT) - is the only unitary system at the tree level that can be constructed by augmenting planar gravity through the curvature-squared terms, is presented. Two interesting gravitational properties of the BHT model, namely, time dilation and time delay, which have no counterpart in the usual Einstein 3D gravity, are analyzed as well.Comment: Submitted to Classical and Quantum Gravit

Tópicos em teoria quântica de campos

Dois tópicos importantes e atuais em teoria quântica de campos, a saber, Teorias com Derivadas de Ordem mais Alta e Determinação de Limites para a Massa do Fóton, são considerados. Como protótipos para as teorias de ordem mais alta selecionamos a Eletrodinâmica de Lee e Wick e a Gravitação Massiva em 3D. Ambas as teorias são de relevância especial para a física contemporânea. A primeira por constituir o alicerce sobre o qual o Modelo Padrão de Lee e Wickse assenta, enquanto que a outra é a única teoria de gravitação com derivadas de ordem mais alta conhecida até o momento cuja versão linearizada é unitária em nível de árvore. Novas e interessantes propriedades relativas às mencionadas teorias são estudadas em detalhe. Finalmente, limites clássicos e quânticos para a massa do fóton são estimadosTwo important and current topics in quantum field theory, namely, Higher-Derivative Theories and Bounds on the Photon Mass, are considered. As prototypes for the higher-order theories we have singled out Lee-Wick Finite Electrodynamics and Massive Gravity in 3D. Both theories are of special relevance to contemporary physics. The former because it is the base on which the Lee-Wick Standard Model rests, while the other is the only higher-order gravity theory known up to now whose linearized version istree-levelunitary. Novel and interesting properties related to both theories area nalyzed in detail. Finally, classical and quantum bounds on the photon mass are estimate

LIMITS on THE COUPLING CONSTANT of HIGHER-DERIVATIVE ELECTROMAGNETISM

We investigate a higher-derivative version of QED constructed by adding to the Maxwell's Lagrangian a term containing second-order derivatives of the electromagnetic potentials. The resulting Lagrangian, besides being gauge and Lorentz invariant, gives origin to local field equations that are linear in the field quantities. Two bounds on the coupling constant of this higher-order model are estimated: one of them is found using the measurements obtained on a lab experiment whose principal aim was to test the Coulomb's inverse square law, the other involves the computation of the anomalous magnetic moment of the electron in the framework of the aforementioned system. As a by-product of the calculations on the quantum limit, a bound on the Lee-Wick heavy photon mass of the same order of magnitude as the masses of the vectorial bosons found in nature, is obtained as well.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Combining general relativity, massive QED and Very Long Baseline Interferometry to gravitationally constrain the photon mass

A constraint between the photon mass and the parameters gamma (the deflection parameter determined by experimentalists) and nu (the photon frequency) is found by judiciously combining General Relativity and Massive QED. By adopting this scenario and by considering as inputs the most recent measurements of the solar gravitational deflection of radio waves obtained by means of the Very Long Baseline Interferometry, gravitational upper bounds on the photon mass are estimated. (C) 2010 Elsevier B.V. All rights reserved.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Gravitational and quantum bounds on the photon mass

Two upper bounds on the photon mass are estimated by means of new conceptual approaches. One of them is found by analyzing the deflection of a massive photon (described by Proca electrodynamics) by an external weak gravitational field. We take as inputs the most recent measurements of the gravitational bending of radio waves by the Sun obtained via the VLBI (very long baseline interferometry). The other one is based on the computation of the anomalous electron magnetic moment in the framework of Proca electrodynamics. The resulting bounds (m(grav) similar to 1.7 x 10(-11) MeV, m(quant) similar to 1.6 x 10(-10) MeV) are of the same order of magnitude as other existing upper limits, but higher than those recently found.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES