Stable cosmology in ghost-free quasidilaton theory

TL;DR

This paper introduces new stable cosmological solutions in ghost-free quasidilaton theory, demonstrating late-time acceleration with stable perturbations and constant graviton masses, suitable for future cosmological modeling.

Contribution

The authors discover three new cosmological branches in ghost-free quasidilaton theory, with one showing perturbative stability and desirable late-time acceleration properties.

Findings

One solution passes stability tests

Graviton masses converge to a constant

All modes propagate at the speed of light

Abstract

We present a novel cosmological solution in the framework of extended quasidilaton theory which underwent scrutiny recently. We only consider terms that do not generate the Boulware-Deser degree of freedom, hence the "ghost-free" quasidilaton theory, and show three new branches of cosmological evolution therein. One of the solutions passes the perturbative stability tests. This new solution exhibits a late time self-acceleration and all graviton polarizations acquire masses that converge to a constant in the asymptotic future. Moreover, all modes propagate at the speed of light. We propose that this solution can be used as a benchmark model for future phenomenological studies.