Spontaneous scalarization of black holes and compact stars from a Gauss-Bonnet coupling

TL;DR

This paper introduces a class of scalar-tensor theories with Gauss-Bonnet coupling that cause spontaneous scalarization in black holes and neutron stars, revealing new dynamical behaviors distinct from general relativity.

Contribution

It demonstrates that certain scalar-tensor theories with Gauss-Bonnet coupling lead to spontaneous scalarization in black holes and stars, expanding understanding of alternative gravity models.

Findings

Black holes scalarize within specific mass bands.

Neutron stars can also undergo scalarization.

Stationary solutions of GR are not always dynamically preferred.

Abstract

We identify a class of scalar-tensor theories with coupling between the scalar and the Gauss-Bonnet invariant that exhibit spontaneous scalarization for both black holes and compact stars. In particular, these theories formally admit all of the stationary solutions of general relativity, but these are not dynamically preferred if certain conditions are satisfied. Remarkably, black holes exhibit scalarization if their mass lies within one of many narrow bands. We find evidence that scalarization can occur in neutron stars as well.