Collapsing dust thin shells in Einstein-Gauss-Bonnet gravity

TL;DR

This paper studies the gravitational collapse of thin shells in Einstein-Gauss-Bonnet gravity, revealing a bounce that prevents singularity formation and results in a novel oscillating black hole structure, supporting cosmic censorship.

Contribution

It demonstrates that in 4D Einstein-Gauss-Bonnet gravity, collapsing shells bounce without forming singularities, introducing a new black hole type with oscillatory behavior.

Findings

Shell bounce prevents singularity formation.

Oscillating shell behavior on Penrose diagram.

Weak cosmic censorship holds.

Abstract

We investigate gravitational collapse of a spherically symmetric thin shell in the Einstein-Gauss-Bonnet (EGB) gravity. Under the recently proposed 4D limit, we find that the collapsing shell will be bounced back at a small radius, without forming a singularity. This bouncing behavior is similar to those of a test particle and a homogeneous spherical dust star, in accordance with the expectation that the Gauss-Bonnet term will modify the small scale behavior of the Einstein gravity. We analyze the causal structure of the dynamic spacetime that represents the bouncing process, finding that the thin shell has an oscillation behavior on the Penrose diagram, which means that the thin shell results in a novel type of black hole with respect to observers outside the event horizon that the collapse forms. We also find that the weak cosmic censorship conjecture holds in this model. Further implications of such a regular gravitational collapse are discussed.