Critical Phenomena Associated with Boson Stars

TL;DR

This paper investigates the critical phenomena at the threshold of black hole formation involving boson stars, revealing that unstable boson stars can lead to dispersal or black hole formation, with implications for neutron star models.

Contribution

It demonstrates that unstable boson stars serve as critical solutions in gravitational collapse, and identifies matter halos as artifacts of scalar field interactions.

Findings

Critical solutions correspond to unstable boson stars.

Small matter halos are artifacts of scalar field collisions.

Unstable boson stars can disperse or form black holes.

Abstract

We present a brief synopsis of related work (gr-qc/0007039), describing a study of black hole threshold phenomena for a self-gravitating, massive complex scalar field in spherical symmetry. We construct Type I critical solutions dynamically by tuning a one-parameter family of initial data consisting of a boson star and a massless real scalar field, and numerically evolving this data. The resulting critical solutions appear to correspond to boson stars on the unstable branch, as we show via comparisons between our simulations and perturbation theory. For low-mass critical solutions, we find small ``halos'' of matter in the tails of the solutions, and these distort the profiles which otherwise agree with unstable boson stars. These halos seem to be artifacts of the collisions between the original boson stars and the massless fields, and do not appear to belong to the true critical solutions. From this study, it appears that unstable boson stars are unstable to dispersal (``explosion'') in addition to black hole formation. Given the similarities in macroscopic stability between boson stars and neutron stars, we suggest that similar phenomena could occur in models of neutron stars.