Universal ratios of critical physical quantities of charged AdS black holes
We investigate the ratios of critical physical quantities related to the T−S criticality of charged AdS black holes. It is shown that the ratio TcSc/Qc is universal while Tcrc/Qc is not. This finding is quite interesting considering the former observation that both the T−S graph and T−r+ graph exhibit reverse van der Waals behavior. It is also worth noting that the value of TcSc/Qc differs from that of Pcvc/Tc for P−V criticality. Moreover, we discuss ratios for the P−V criticality and Q−Φ criticality. By introducing the dimensional analysis technique, we successfully interpret the phenomenon that the ratio ΦcQc/Tc is not universal and construct two universal ratios for the Q−Φ criticality instead. It is expected that the dimensional analysis technique can be generalized to probe the universal ratios for Y−X criticality in future research.