Bigravity and Horndeski gravity connected by a disformal coupling

TL;DR

This paper explores a bi-gravity model with a disformal coupling, showing it can produce late-time cosmic acceleration but faces tight observational constraints requiring fine-tuning.

Contribution

It introduces a specific bi-gravity model with a disformal coupling and analyzes its cosmological implications focusing on one degree of freedom.

Findings

Model can produce late-time cosmic acceleration as an attractor.

Observational constraints from tensor perturbations are very stringent.

Model requires significant fine-tuning to satisfy observational bounds.

Abstract

In this paper, we have studied bi-gravity theory in a very specific limit where we focused only on one degree of freedom generated by the massive graviton. We have analyzed the model in the context of cosmology and demonstrated that the model can give rise to late time cosmic acceleration as an attractor of the dynamical system. However, the observational constraints due to tensor perturbations are stringent giving rise to large fine tuning.