Spacetime symmetries and varying scalars

TL;DR

This paper explores how spacetime-dependent scalar fields in cosmological supergravity models can lead to Lorentz symmetry violation and affect electromagnetic parameters like alpha and theta, linking scalar dynamics to observable Lorentz- and CPT-violating effects.

Contribution

It demonstrates a specific model where scalar fields with time-dependent expectation values induce Lorentz violation and modify electromagnetic couplings.

Findings

Scalar fields can acquire time-dependent expectation values in cosmological models.

Scalar excitations exhibit Lorentz-breaking dispersion relations.

Couplings to electromagnetism cause variations in alpha and theta, linked to Lorentz and CPT violation.

Abstract

This talk discusses the relation between spacetime-dependent scalars, such as couplings or fields, and the violation of Lorentz symmetry. A specific cosmological supergravity model demonstrates how scalar fields can acquire time-dependent expectation values. Within this cosmological background, excitations of these scalars are governed by a Lorentz-breaking dispersion relation. The model also contains couplings of the scalars to the electrodynamics sector leading to the time dependence of both the fine-structure parameter alpha and the theta angle. Through these couplings, the variation of the scalars is also associated with Lorentz- and CPT-violating effects in electromagnetism.