Cosmic Expansion in Extended Quasidilaton Massive Gravity

TL;DR

This paper explores a modified gravity theory called quasidilaton massive gravity, deriving equations for cosmic expansion and showing it can explain late-time acceleration and CMB anomalies through a massive graviton.

Contribution

It provides the full dynamical equations for the universe's expansion in quasidilaton massive gravity and discusses constraints on model parameters for self-consistent solutions.

Findings

Self-consistent solutions constrain model parameters.

Effective gravitational wave mass can exceed graviton mass.

Theory can account for cosmic acceleration and CMB anomalies.

Abstract

Quasidilaton massive gravity offers a physically well-defined gravitational theory with non-zero graviton mass. We present the full set of dynamical equations governing the expansion history of the universe, valid during radiation domination, matter domination, and a late-time self-accelerating epoch related to the graviton mass. The existence of self-consistent solutions constrains the amplitude of the quasi-dilaton field and the graviton mass, as well as other model parameters. We point out that the effective mass of gravitational waves can be significantly larger than the graviton mass, opening the possibility that a single theory can explain both the late-time acceleration of the cosmic expansion and modifications of structure growth leading to the suppression of large-angle correlations observed in the cosmic microwave background.