Anisotropic Friedmann-Robertson-Walker universe from nonlinear massive gravity

TL;DR

This paper investigates a nonlinear massive gravity model revealing a new anisotropic attractor solution where the universe appears isotropic at the background level but exhibits anisotropic features in perturbations, with implications for cosmological observations.

Contribution

It introduces a novel anisotropic attractor solution in nonlinear massive gravity where the physical metric is isotropic but the Stuckelberg fields are anisotropic, expanding understanding of anisotropic cosmologies.

Findings

Discovery of a new anisotropic attractor with isotropic physical metric

Background universe appears homogeneous and isotropic

Perturbations show suppressed statistical anisotropy

Abstract

In the scope of the nonlinear massive gravity, we study fixed points of evolution equations for a Bianchi type--I universe. We find a new attractor solution with non-vanishing anisotropy, on which the physical metric is isotropic but the Stuckelberg configuration is anisotropic. As a result, at the background level, the solution describes a homogeneous and isotropic universe, while a statistical anisotropy is expected from perturbations, suppressed by smallness of the graviton mass.