Stable Cosmology from Minimal Theory of Mass-Varying Massive Gravity

TL;DR

This paper investigates a minimal extension of mass-varying massive gravity, demonstrating its stable cosmological solutions and potential to explain dark energy or inflation consistent with observations.

Contribution

It introduces the minimal theory of mass-varying massive gravity (MTMVMG), showing it is free from instabilities and can account for dark energy or inflation.

Findings

Stable cosmological solutions without ghost or tachyonic instabilities

Scalar field can act as dark energy or inflaton

Consistent with current cosmological observations

Abstract

We study cosmological perturbations in the minimal theory of mass-varying massive gravity (MTMVMG), a constrained extension of mass-varying massive gravity that propagates only three physical degrees of freedom. We show that MTMVMG admits a stable cosmological solutions i.e. free from ghost, gradient, and tachyonic instabilities around the homogeneous and isotropic background. We further demonstrate that the dynamical external scalar field$\textendash\textendash$which is responsible for the mass of the graviton$\textendash\textendash$can suitably serve as either dark energy or the inflaton, yielding a description consistent with current cosmological observations.