Black hole accretion of scalar clouds with spontaneous symmetry breaking

TL;DR

This paper investigates how spontaneous symmetry breaking influences scalar cloud accretion onto black holes, revealing unstable phases, non-degenerate accretion channels, and characteristic energy bands in the evolution process.

Contribution

It demonstrates the existence of unstable symmetry-breaking phases that lead to scalar cloud formation and affects accretion dynamics in black hole environments.

Findings

Symmetry-breaking phases are unstable to scalar cloud formation.

Accretion channels become non-degenerate due to symmetry breaking.

Final states exhibit a characteristic energy band from radiation variations.

Abstract

Spontaneous scalarization of black holes typically occurs through the condensation of a scalar field, with the field evolving from a $U(1)$-symmetric phase into a symmetry-breaking one with lower energy. We show that there exist symmetry-breaking phases which are themselves unstable to the formation of an additional scalar condensate, or `cloud', which is partly accreted into the black hole. By studying the fully nonlinear dynamical evolution of the process, we find that symmetry breaking causes the accretion channels of scalar clouds to be non-degenerate, favoring a dominant channel for evolution. Additionally, the final states form a characteristic energy band due to varying amounts of radiation emitted by clouds in different channels.