The quantum fate of black hole horizons

Understand

The presence of a horizon is the principal marker for black holes as they appear in the classical theory of gravity.

• In General Relativity (GR), horizons have several defining properties.
• First, there exists a static spherically symmetric solution to vacuum Einstein equations which possesses a horizon defined as a null-surface on which the time-like Killing vector becomes null.
• Second, in GR, a co-dimension two sphere of minimal area is necessarily a horizon.