Exploring critical behavior of thermodynamic variables of the Kerr-Newman-AdS black hole in the restricted phase space

Abstract: The present work delves into examining the thermodynamic properties of the four-dimensional Kerr-Newmann-AdS black hole, employing the recently proposed framework of restricted phase space thermodynamics (RPST). This approach introduces a novel set of paired thermodynamic variables: the central charge $C$ of the corresponding dual conformal field theory (CFT) and the chemical potential $\mu$. Through simple analysis, we establish fundamental relationships such as the Euler relation, Gibbs-Duhem relation, and the zeroth order homogeneity of intensive variables. Employing numerical techniques, we explore the thermodynamic processes between these conjugate variables. Our investigation reveals the first-order and second-order phase transitions across various macroscopic processes. Despite the absence of complete analytical expressions, our findings unveil striking similarities in behavior between RN-AdS and Kerr-AdS, underscoring the presence of underlying universality within the RPST formalism.