Thermodynamic instabilities of generalized exotic BTZ black holes

Abstract

Abstract We examine the conjecture that black holes violating the reverse isoperimetric inequality have negative specific heat at constant volume C V [1]. We test this conjecture on the family of generalized exotic Bañados, Teitelboim and Zanelli (BTZ) black holes and find that C V can be positive even when the reverse isoperimetric inequality is violated, providing a counter example to the conjecture. However in all cases where C V is positive, the specific heat at constant pressure C P is negative, indicating that generalized exotic black holes are thermodynamically unstable, suggesting that a broader version of the conjecture might hold.