Black Hole Singularity Described as a Surface, Not a Point

Redefining the Black Hole Singularity

A recent paper posits that the singularity within a black hole is a surface rather than a point, contrary to popular belief. This distinction arises because two observers free-falling into a spherical black hole from different angular trajectories will not meet at a central point singularity; instead, they lose causal contact well before reaching it.

Causal Disconnect in General Relativity

In general relativity, it is possible for two spatially close points to be causally distant. This phenomenon contributes to the understanding of the singularity as a surface. For rotating black holes, the singular surface is located at the inner horizon, where even minor perturbations can trigger an exponential mass inflation instability, leading to collapse into a spacelike singular surface.

Implications for Quantum Gravity

This reinterpretation of the black hole singularity has consequences for quantum gravity theories. The paper suggests that the quantum states of a black hole likely reside on its effectively two-dimensional singular surface. This surface is theorized to coevolve unitarily and remain in thermodynamic equilibrium with the hot atmosphere of trapped Hawking radiation generated within the black hole's event horizon.