Vainshtein Screening in Bimetric Cosmology

TL;DR

This paper shows that the instabilities in bimetric cosmology are due to the non-linear Vainshtein mechanism, and it uses this understanding to analyze cosmological data, resolving the Hubble tension with an effective phantom dark energy.

Contribution

It reveals the connection between linear instabilities and the non-linear Vainshtein mechanism in bimetric theory, providing a new approach to address early universe cosmology.

Findings

Bimetric cosmology's instabilities are linked to the Vainshtein mechanism.

The spin-2 mass defines the cosmological Vainshtein scale.

The model resolves the Hubble tension with an effective phantom dark energy.

Abstract

We demonstrate that the instabilities in linear cosmological perturbations in bimetric theory are the manifestation of the non-linear Vainshtein mechanism on an FRW background. The spin-2 mass serves as the cosmological Vainshtein scale in this case. This allows us to quantitatively address early universe cosmology. In particular, in a global analysis, we study data from the cosmic microwave background radiation and local measurements of the Hubble flow. We show that bimetric cosmology resolves the discrepancy in the local and early-time measurements of the Hubble scale via an effective phantom dark energy component.