Divergence Behavior of Thermodynamic Curvature Scalar at Critical Point in the extended Phase Space of generic Black Holes.

The $P$-$V$ phase transition and critical behavior in the extended phase space of asymptotic Anti-de Sitter (AdS) black holes have been widely investigated, in which four critical exponents around critical point are found to be consistent with values in mean field theory. Recently, another critical exponent $\nu$ related to divergent correlation length at critical point has been investigated by using thermodynamic curvature scalar $R_N$ at critical point in charged AdS black hole. Moreover, one finds that the divergence behavior of $R_N$ at critical point indicates a universal property, i.e. characterized by a dimensionless constant that is identical to that for a van der Waals fluid. In this paper, we further check out this universal property through investigating thermodynamic curvature scalar in de Rham-Gabadadze-Tolley (dRGT) massive gravity, and find that this dimensionless constant is also indeed independent of horizon topology, massive graviton and dimension of spacetime. Furthermore, we investigate divergence behavior of thermodynamic curvature scalar at critical point in generic asymptotic Anti-de Sitter (AdS) black holes, and demonstrate the universality in this generic case. Those results give new insights into the microstructure of black holes.