Embedding black holes and other inhomogeneities in the universe in various theories of gravity: a short review

Understand

The classic black hole mechanics and thermodynamics are formulated for stationary black holes with event horizons.

• Alternative theories of gravity of interest for cosmology contain a built-in time-dependent cosmological "constant" and black holes are not stationary.
• Realistic black holes are anyway dynamical because they interact with astrophysical environments or, at a more fundamental level, because of backreaction by Hawking radiation.
• In these situations the teleological concept of event horizon fails and apparent or trapping horizons are used instead.