Spherical non-linear absorption of cosmological scalar fields onto a black hole

TL;DR

This study investigates how massless scalar fields non-linearly evolve and are absorbed by black holes, revealing conditions under which scalar fields can survive outside black holes over cosmological timescales.

Contribution

It provides the first analysis of non-linear spherical scalar field accretion onto black holes, highlighting the impact of wave number and width on absorption outcomes.

Findings

For zero wave number and large width, absorption is incomplete.

For positive wave numbers, the black hole absorbs all scalar field energy.

Scalar fields can survive outside black holes over cosmological timescales.

Abstract

In this paper we track the non-linear spherical evolution of a massless scalar field onto a Schwarzschild black hole space-time as a first approximation to the accretion of cosmologically motivated classical scalar fields. We perform an analysis related to wave packets described by wave number and width. We study various values of the wave number k, and found that for k = 0 and width packets bigger than the Schwarzschild radius, the absorption is not total. In the cases we studied for k > 0, the black hole absorbs the total amount of energy density of the scalar field moving toward the horizon. Our results indicate that assuming spherical symmetry, in the non-linear regime, there are cases for which scalar fields are allowed to survive outside black holes and may eventually have life-times consistent with cosmological time scales.