On the stability of bimetric structure formation

TL;DR

This paper demonstrates that a simple bimetric gravity model can produce stable structure formation solutions, showing no physical instabilities and potential observable differences from standard cosmology.

Contribution

It provides an analytical solution to structure formation in bimetric gravity, confirming stability and highlighting measurable deviations from ΛCDM.

Findings

Analytical solution shows no physical instability.

Model yields measurable differences from ΛCDM.

Structure growth remains well-behaved.

Abstract

Bimetric gravity can reproduce the accelerated expansion of the Universe, without a cosmological constant. However, the stability of these solutions to linear perturbations has been questioned, suggesting exponential growth of structure in this approximation. We present a simple model of structure formation, for which an analytical solution is derived. The solution is well-behaved, showing that there is no physical instability with respect to these perturbations. The model can yield a growth of structure exhibiting measurable differences from $\Lambda$CDM.