Lightning over the Horizon: The Collapse of Semiclassical Gravity in Black Hole Evaporation ✦

Original: "Breakdown of Semiclassical Gravity in Four-Dimensional Black Hole Evaporation"

arXiv:2605.00780v1 · 2026-05-01 · CC BY · ⏱ 1 min · HEP Theory General Relativity

Numerical simulation of black hole evaporation has revealed for the first time a catastrophic spacelike singularity — a thunderbolt — that refutes semiclassical gravity on macroscopic scales.

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The black hole evaporates, and with it, confidence in the semiclassical picture vanishes. The simulation uncovered an unexpected finale: a thunderbolt — a spacetime lightning — pierces reality where it was least expected. Semiclassical gravity predicted its own collapse. This demands a completely new approach to quantum gravity and forces a reexamination of the nature of information.

🎯 Hawking and Stewart called this phenomenon a "thunderbolt" in 1993, but considered it a mathematical curiosity. Four-dimensional modeling with quantum corrections turned the curiosity into an inevitability, showing that even the term's creator underestimated its reality.

ds^2 = -e^{2\rho} du dv + r^2 d\Omega^2

Spacetime geometry: u and v are retarded and advanced time, r is the radial coordinate determining the area of the 2-sphere.

K = R_{\mu\nu\lambda\rho} R^{\mu\nu\lambda\rho}

Invariant measure of curvature: sum of squares of all components of the Riemann tensor; shows how strongly spacetime is curved at each point.

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Lightning over the Horizon: The Collapse of Semiclassical Gravity in Black Hole Evaporation ✦