Possible Lorentz symmetry violation from broken Weyl invariance

TL;DR

This paper explores how breaking Weyl invariance in a gravity-scalar theory can lead to Lorentz symmetry violation, generating CPT-odd interactions and analyzing phase features and naturalness of the model.

Contribution

It introduces a model where Weyl invariance breaking induces Lorentz violation and discusses the resulting phases and naturalness considerations.

Findings

Lorentz violation arises from Weyl symmetry breaking.

A CPT-odd Lorentz-violating interaction is generated.

The light mass scale is protected from large corrections.

Abstract

In this work, we investigate a theory of linear Weyl gravity coupled to a scalar field and study the scenario in which Lorentz symmetry is broken by a non-vanishing vacuum expectation value of the Weyl field in the flat space limit after Weyl symmetry breaking. We show that a $CPT$-odd Lorentz-violating interaction is generated after symmetry breaking. Features of different symmetry-broken phases and their dependence on the spacetime character of the generated Lorentz-violating background are discussed. Also, we analyze the naturalness of the theory by showing that the light mass scale is protected from large radiative corrections due to an enhanced spacetime symmetry.