Article

# Addendum: Ultrahigh-energy cosmic-ray bounds on nonbirefringent modified-Maxwell theory

Physical review D: Particles and fields 07/2008; DOI: 10.1103/PHYSREVD.77.117901

Source: arXiv

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**ABSTRACT:**Assuming Lorentz symmetry is broken by some fixed vector background, we study the spinor electrodynamics modified by two dimension-five Lorentz-violating interactions between fermions and photons. The effective polarization and magnetization are identified from the modified Maxwell equations, and the theoretical consequences are investigated. We also compute the corrections to the relativistic energy levels of hydrogen atom induced by these Lorentz-violating operators in the absence and presence of uniform external fields in first-order perturbation theory. We find that the hydrogen spectrum is insensitive to the breakdown of Lorentz boost symmetry.Physical review D: Particles and fields 04/2013; 87(12). - [Show abstract] [Hide abstract]

**ABSTRACT:**Physics beyond the Fermi scale could show up through deviations of the gauge couplings predicted by the electroweak Yang-Mills sector. This possibility is explored in the context of the International Linear Collider (ILC) through the helicity amplitudes for the gamma e -> W nu_e reaction to which contributes the trilinear WWgamma coupling. The new physics effects on this vertex are parametrized in a model-independent fashion through an effective electroweak Yang-Mills sector, which is constructed by considering two essentially different sources of new physics. In one scenario, Lorentz violation will be considered exclusively as the source of new physics effects. This type of new physics is considered in an extension of the Standard Model that is known as the Standard Model Extension (SME), which is an effective field theory that contemplates CPT and Lorentz violation in a model-independent fashion. Any source of new physics that respects the Lorentz symmetry, will be considered within the general context of the well known Conventional Effective Standard Model (CESM) extension. Both the SME and the CESM descriptions include gauge invariant operators of dimension higher than four, which, in general, transform as Lorentz tensors of rank higher than zero. Whereas in the former theory observer Lorentz invariants are constructed by contracting these operators with constant Lorentz tensors, in the latter the corresponding Lorentz invariant interactions are obtained contracting such operators with products of the metric tensor. We focus our study on the possibility of experimentally distinguish both types of new physics effects on the WWgamma vertex. It is found that for a new physics scale of the same order of magnitude and under determined circumstances, both types of new physics effects will be clearly distinguished.05/2013; - [Show abstract] [Hide abstract]

**ABSTRACT:**Considering quantum gravity within the framework of effective field theory, we investigated the consequences of spontaneous Lorentz violation for the gravitational potential. In particular, we focus our attention on the bumblebee models, in which the graviton couples to a vector $B_{\mu}$ that assumes a nonzero vacuum expectation value. The leading order corrections for the nonrelativistic potential are obtained from calculation of the scattering matrix of two scalar particles interacting gravitationally. These corrections imply anisotropic properties associated with the bumblebee background and also add a Darwin-like term for Newton's potential.Physical Review D 04/2013; 88:025005. · 4.69 Impact Factor

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