Black hole singularities reportedly form 2D surfaces not zero-dimensional points in general relativity

The paper challenges the textbook picture of a black-hole singularity as a dimensionless point. Instead, it shows that free-falling observers on different angular trajectories lose causal contact before reaching any central point, indicating the singularity must be a two-dimensional surface. This conclusion follows directly from the causal structure of the Schwarzschild and Kerr metrics, without invoking new physics.

For engineers building relativistic simulation codes, the finding implies that existing point-singularity boundary conditions may need revision. Numerical grids that terminate at a single point will fail to capture the full geometry; instead, a surface boundary must be implemented. The authors suggest that the surface is where quantum information is stored, which could simplify unitary evolution models of black-hole evaporation.

The rotating case is more complex because the inner horizon is unstable to mass inflation. Any perturbation, classical or quantum, triggers exponential growth of the mass function, collapsing the inner horizon into a spacelike singular surface. This instability must be included in any rotating-black-hole simulation, increasing computational cost but potentially resolving long-standing questions about Cauchy horizons.

Implications for quantum gravity are speculative but concrete. If the singular surface is the locus of quantum states, then the black-hole entropy formula may be reinterpreted as counting surface degrees of freedom rather than bulk microstates. This aligns with holographic principles but shifts the focus from the event horizon to the singular surface itself, which lies inside the trapped region and co-evolves with Hawking radiation.