Fate of gravitational collapse in semiclassical gravity

TL;DR

This paper critically examines the formation of trapping horizons during gravitational collapse in semiclassical gravity, suggesting that such horizons may not form in many realistic scenarios, potentially leading to alternative collapsed objects.

Contribution

It challenges the standard black hole formation paradigm in semiclassical gravity, proposing that trapping horizons might not always form during collapse.

Findings

Trapping horizon formation can be seriously questioned in many realistic scenarios.

Semiclassical physics may prevent the formation of trapping horizons.

Alternative collapsed objects could exist without traditional black holes.

Abstract

While the outcome of gravitational collapse in classical general relativity is unquestionably a black hole, up to now no full and complete semiclassical description of black hole formation has been thoroughly investigated. Here we revisit the standard scenario for this process. By analyzing how semiclassical collapse proceeds we show that the very formation of a trapping horizon can be seriously questioned for a large set of, possibly realistic, scenarios. We emphasise that in principle the theoretical framework of semiclassical gravity certainly allows the formation of trapping horizons. What we are questioning here is the more subtle point of whether or not the standard black hole picture is appropriate for describing the end point of realistic collapse. Indeed if semiclassical physics were in some cases to prevent formation of the trapping horizon, then this suggests the possibility of new collapsed objects which can be much less problematic, making it unnecessary to confront the information paradox or the run-away end point problem.