Black Hole Chemistry: the first 15 years

TL;DR

Black Hole Chemistry explores the thermodynamic behavior of black holes, revealing complex phase transitions and phenomena analogous to chemical systems, significantly advancing our understanding of gravitational physics over the past 15 years.

Contribution

This paper reviews the development of Black Hole Chemistry, highlighting new phenomena and concepts such as multicriticality, superfluid transitions, and holography since its inception.

Findings

Black holes exhibit Van der Waals-like phase transitions.

Discovery of reentrant and triple point phase behaviors.

Introduction of concepts like thermodynamic topology and microstructure.

Abstract

The introduction of thermodynamics into gravitational physics began 5 decades ago with the discovery that black holes behave like thermodynamic systems once semiclassical quantum effects are taken into account. Notions of temperature, entropy, work, and phase changes that were introduced into gravitational physics and originally applied to black holes, were later extended to cosmological horizons and other settings as well. A major development occurred 15 years ago with the introduction of pressure in the form of a cosmological constant. By extending the thermodynamic phase space to include this term, along with its conjugate volume, black holes were found to exhibit a broad variety of phase transitions that resembled phenomena seen in chemistry labs. Black hole thermodynamics has become Black Hole Chemistry, which has led to a wealth of insights into the nature of black holes, introducing concepts such as Van der Waals fluids, reentrant phase transitions, and triple points into gravitational physics. I discuss the origins of Black Hole Chemistry and its basic features covered in an earlier review [1], and then go on to describe developments in the subject that have taken place since then. Examples include multicritical behaviour, polymeric transitions, superfluid transitions, scalar hair, heat engines, NUT-charge, acceleration thermodynamics, the Joule-Thompson expansion, holography, complexity, central charge criticality, microstructure, thermodynamic tension, phase dynamics, and thermodynamic topology. This wealth of new phenomena suggest that we likely still have a lot to learn from Black Hole Chemistry.