Impact of Lorentz violation on the dynamics of inflation

TL;DR

This paper explores how spontaneous Lorentz violation affects inflationary dynamics in scalar-vector-tensor gravity, providing new exact solutions and conditions for solving horizon and flatness problems, including scenarios without inflaton potential.

Contribution

It introduces a first-order formalism to derive new exact Lorentz violating inflationary solutions across various models, including potential-free cases.

Findings

Different conditions are needed to solve horizon and flatness problems.

A necessary condition for inflation to address both problems is identified.

Superinflation may be required in models without inflaton potential.

Abstract

This work deals with the dynamics of inflation in the context of a scalar-vector-tensor theory of gravity exhibiting spontaneous Lorentz violation at early times. We describe a first-order formalism which we use to obtain new exact Lorentz violating inflationary solutions for a broad family of models, some in the absence of a potential for the inflaton field. Our results show that different conditions are required to solve the horizon and flatness problems. In particular, we find a necessary condition for inflation to provide a solution to both problems and we show that in inflationary models with no inflaton potential a period of superinflation might be necessary to solve the flatness problem.