March 3, 2026Open Access

The upper bound of event horizon formation time in generalized Oppenheimer–Snyder collapse

Key Points

Event horizon formation time is maximized at Δ T eh = 196 m, suggesting key limits for black hole formation.
The findings pertain specifically to static, spherically-symmetric black holes satisfying the weak energy condition.
Assessment involved the Oppenheimer-Snyder collapse within the context of asymptotically flat geometries.
This work extends traditional inequalities in black hole physics to include temporal constraints.

Abstract

We prove that, in the framework of the Oppenheimer-Snyder collapse, the Schwarzschild exterior maximizes the event horizon formation time Δ T eh = 19 6 m among all asymptotically flat, static, spherically-symmetric black holes with the same ADM mass m that satisfy the weak energy condition. This bound extends the typical black hole inequalities–such as the Penrose inequality, which constrains spatial geometry–to temporal setting.

The upper bound of event horizon formation time in generalized Oppenheimer–Snyder collapse

Key Points

Abstract

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