Gravitational entropy: beyond the black hole
Hawking established that black hole area may be identified with entropy, thus establishing a generalized second law of thermodynamics. Cosmological event horizon area may be regarded similarly, the most important case being de Sitter space, which can be applied to inflation. But how far can the generalized second law be generalized? Does it apply to all event horizons, even when time-dependent? I shall explore the scope of the generalized second law and also show that it can be used to rule out the existence of Dirac monopoles.