Cosmology and perturbations in tachyonic massive gravity

TL;DR

This paper introduces a new tachyonic extension of dRGT massive gravity, analyzes its cosmological solutions, and studies gravitational wave propagation, offering insights for future cosmological and gravitational wave research.

Contribution

It presents a novel tachyonic extension of dRGT massive gravity, derives cosmological solutions, and examines gravitational wave dispersion in this framework.

Findings

Derived self-accelerating cosmological solutions.

Calculated gravitational wave dispersion relations.

Analyzed tensor, vector, and scalar perturbations.

Abstract

As massive gravity and its extensions offer physically well-defined gravitational theories with a nonzero graviton mass, we present a new extension of the de Rham-Gabadadze-Tolley (dRGT)massive gravity, which is tachyonic massive gravity theory. We firstly introduce the new extension of the dRGT massive gravity, constructed by adding a tachyonic term. We then find the cosmological background equations, and present the analysis of self-accelerating solutions. We examine the tensor perturbations to calculate the dispersion relation of gravitational waves (GWs). In a special case, we consider a constant tachyon potential for the tachyon field, and calculate the equations of motion and self-accelerating solutions. Finally, we investigate the background perturbations, which include tensor, vector, and scalar perturbations in this case. We calculate the dispersion relation of GWs in the FLRW cosmology in a tachyonic massive gravity theory. These analyses provide potential inputs to future applications in cosmology and GWs propagation.