Thermodynamics of horizons: de Sitter black holes and reentrant phase transitions

Understand

In this paper we propose a straightforward method for understanding the thermodynamics of black holes in de Sitter space, one that will allow us to study these black holes in a way that is analogous to the anti-de Sitter case.

• As per usual, we formulate separate thermodynamic first laws for each horizon present in the spacetime, and study their thermodynamics as if they were independent systems characterized by their own temperature.
• That these systems are not entirely independent and various thermodynamic quantities in them are in fact "correlated" is reflected by the fact that their thermodynamics can be captured by a single Gibbs free energy-like thermodynamic potential.
• This quantity contains information about possible phase transitions in the system and allows us to uncover a rich phase structure for de Sitter black holes.