On the Hawking radiation as tunneling for a class of dynamical black holes

Understand

The instability against emission of massless particles by the trapping horizon of an evolving black hole is analyzed with the use of the Hamilton-Jacobi method.

• The method automatically selects one special expression for the surface gravity of a changing horizon.
• Indeed, the strength of the horizon singularity turns out to be governed by the surface gravity as was defined a decade ago by Hayward using Kodama's theory of spherically symmetric gravitational fields.
• The theory also applies to point masses embedded in an expanding universe, were the surface gravity is still related to Kodama-Hayward theory.