Critical behavior of AdS black holes surrounded by dark fluid with Chaplygin-like equation of state

TL;DR

This paper investigates the thermodynamic phase transitions and shadow properties of AdS black holes surrounded by a dark fluid with a Chaplygin-like equation of state, revealing Van der Waals-like behavior and observational signatures.

Contribution

It introduces a new black hole solution with dark fluid, analyzes its critical behavior in extended and non-extended phase spaces, and links shadow radius to phase transitions.

Findings

Existence of Van der Waals-like small/large black hole phase transition.

Shadow radius correlates positively with event horizon radius.

Shadow radius can serve as an observable for black hole phase transitions.

Abstract

Supposing the existence of Dark Fluid with a Chaplygin-like equation of state $p=-B/\rho$ (CDF) as a cosmic background, we obtain a static spherically-symmetric black hole (BH) solution to the Einstein gravitational equations. We study the $P-V$ critical behavior of AdS BH surrounded by the CDF in the extended phase space where the cosmological constant appears as pressure, and our results show the existence of the Van der Waals like small/large BH phase transition. Also, it is found that such a BH displays a first-order low/high-$\Phi$ BH phase transition and admits the same criticality with van der Waals liquid/gas system in the non-extended phase space, where the normalization factor $q$ is considered as a thermodynamic variable, while the cosmological constant being fixed. In both $P-V$ and the newly proposed $q-\Phi$ phase spaces, we calculate the BH equations of state and then numerically study the corresponding critical quantities. Moreover, the critical exponents are derived and the results show the universal class of the scaling behavior of thermodynamic quantities near criticality. Finally, we study the shadow thermodynamics of AdS BHs surrounded by the CDF. We find that, there exists a positive correlation between the shadow radius and the event horizon radius in our case. By analyzing the temperature and heat capacity curves under the shadow context, we discover that the shadow radius can replace the event horizon radius to demonstrate the BH phase transition process, and the changes of the shadow radius can serve as order parameters for the small/large BH phase transition, indicating that the shadow radius could give us a glimpse into the BH phase structure from the observational point of view.