Classification of Oppenheimer-Snyder Collapse: Singular, Bouncing, and Soft-Landing Scenarios

TL;DR

This paper classifies Oppenheimer-Snyder gravitational collapse scenarios into singular, bouncing, and soft-landing types, analyzing conditions for different horizon features and their implications for cosmic censorship.

Contribution

It introduces a comprehensive classification of OS collapse outcomes based on horizon behavior and extends understanding beyond Schwarzschild to Reissner-Nordström and regular black holes.

Findings

Reissner-Nordström collapse exhibits bouncing and horizon vertex features.

Regular black holes with de Sitter cores collapse smoothly without bounce.

Collapse types align with Penrose's strong cosmic censorship conjecture.

Abstract

We study Oppenheimer-Snyder (OS) gravitational collapse matched to a general static, spherically symmetric exterior spacetime. Unlike the Schwarzschild case, two new features can arise in black holes with two horizons: an apparent-horizon left vertex, a temporary minimum in the apparent-horizon radius during collapse, and a bounce, where the star surface stops collapsing at a nonzero radius and reverses into expansion. We identify the conditions that lead to these two features. For two-horizon exteriors, trapped-region consistency requires that the apparent-horizon turning point occurs no earlier than the surface crossing of the inner horizon. As a concrete example, the OS collapse of the Reissner-Nordstr\"om (RN) spacetime shows both effects. In contrast, regular black holes with de Sitter cores show neither: their collapse is smooth and monotonic, and the surface approaches the center only as the proper time goes to infinity. These results naturally classify the OS collapses into three categories: singular, which ends at the center in finite time; bouncing, which reverses at a finite radius; and soft-landing, which reaches the center only asymptotically. We argue that these features are consistent with Penrose's strong cosmic censorship conjecture.