Frozen states of charged boson stars

TL;DR

This paper investigates frozen states of charged boson stars, revealing their structure, stability features, and the role of self-interaction and alternative gravity theories in their existence.

Contribution

It introduces the concept of frozen states in charged boson stars, highlighting the importance of scalar self-interaction and Horndeski gravity in their formation.

Findings

Frozen states are regular solutions with a de Sitter interior and black hole exterior.

Self-interaction of scalar fields is crucial for these solutions in standard electrodynamics.

Horndeski gravity allows frozen states without scalar self-interaction.

Abstract

In this paper, we study frozen states of charged boson stars. These solutions are globally regular and exist in a U(1) gauged scalar field model minimally coupled to gravity for suitable choices of the coupling constants. These configurations are field theoretical realizations of the Mazur-Mottola solution with a de Sitter interior, a black hole exterior and a thin shell that interpolates between the two and replaces the event horizon. We demonstrate that standard electrodynamics is sufficient to find these frozen states, but that the self-interaction of the scalar field is crucial. Adding Horndeski vector-tensor gravity to the model allows the frozen states to exist without self-interaction though. The frozen states possess one stable and one unstable lightring, the former inside the thin shell, the latter in the black hole exterior.