On stars, galaxies and black holes in massive bigravity

TL;DR

This paper explores the behavior of stars, galaxies, and black holes within massive bigravity theories, providing parameter constraints for viable stellar solutions and discussing the formation of black holes from stars.

Contribution

It offers new parameter conditions for star solutions in massive bigravity and analyzes the likelihood of black hole formation from stars.

Findings

Parameter conditions for viable star solutions when star radius is much smaller than graviton Compton wavelength.

Constraints on the ratio of coupling constants for neutron star viability.

Discussion on the unlikelihood of black holes forming from stars due to different asymptotic structures.

Abstract

In this paper we study the phenomenology of stars and galaxies in massive bigravity. We give parameter conditions for the existence of viable star solutions when the radius of the star is much smaller than the Compton wavelength of the graviton. If these parameter conditions are not met, we constrain the ratio between the coupling constants of the two metrics, in order to give viable conditions for e.g. neutron stars. For galaxies, we put constraints on both the Compton wavelength of the graviton and the conformal factor and coupling constants of the two metrics. The relationship between black holes and stars, and whether the former can be formed from the latter, is discussed. We argue that the different asymptotic structure of stars and black holes makes it unlikely that black holes form from the gravitational collapse of stars in massive bigravity.