Gravitational collapse of k-essence

TL;DR

This paper presents numerical simulations of gravitational collapse involving k-essence fields, revealing unique horizon structures and conditions under which signals can escape black holes due to superluminal sound speeds.

Contribution

It introduces the first detailed numerical analysis of black hole formation with k-essence fields, highlighting the existence of dual horizons and superluminal signal escape.

Findings

Black holes form with two horizons: light and sound.

Superluminal k-essence signals can escape when the sound horizon is inside the light horizon.

Horizon merging prevents escape of signals from the black hole.

Abstract

We perform numerical simulations of the gravitational collapse of a k-essence scalar field. When the field is sufficiently strongly gravitating, a black hole forms. However, the black hole has two horizons: a light horizon (the ordinary black hole horizon) and a sound horizon that traps k-essence. In certain cases the k-essence signals can travel faster than light and the sound horizon is inside the light horizon. Under those circumstances, k-essence signals can escape from the black hole. Eventually, the two horizons merge and the k-essence signals can no longer escape.