Thermodynamic stability and P-V criticality of nonsingular-AdS black holes endowed with clouds of strings

TL;DR

This paper studies the thermodynamics and phase transitions of nonsingular-AdS black holes with clouds of strings, revealing that these clouds influence phase transition radii but do not alter critical exponents, maintaining Van der Waals-like behavior.

Contribution

It introduces the analysis of clouds of strings in nonsingular-AdS black holes, showing their effect on phase transition radii without changing critical exponents or the nature of phase transitions.

Findings

Clouds of strings do not affect the SBH/LBH phase transition but shift it to larger horizon radii.

First-order phase transitions resemble liquid-gas transitions, with swallowtail behavior in G–T plots.

Critical exponents match Van der Waals fluid, unaffected by string clouds.

Abstract

We investigate the extended phase space thermodynamics of nonsingular-AdS black holes minimally coupled to clouds of strings in which we consider the cosmological constant ($\Lambda$) as the pressure ($P$) of the black holes and its conjugate variable thermodynamical volume ($V$) of the black holes. Owing to the background clouds of strings parameter ($a$), we analyse the Hawking temperature, entropy and specific heat on horizon radius for fixed-parameter $k$. We find that the strings clouds background does not alter small/large black hole (SBH/LBH) phase transition but occurs at a larger horizon radius, and two second-order phase transitions occur at a smaller horizon radius. Indeed, the $G$--$T$ plots exhibit a swallowtail below the critical pressure, implying that the first-order phase transition is analogous to the liquid-gas phase transition at a lower temperature and lower critical pressure. To further examine the analogy between nonsingular-AdS black holes and a liquid-gas system, we derive the exact critical points and probe the effects of a cloud of strings on $P-V$ criticality to find that the isotherms undergo liquid-gas like phase transition for $\tilde{T}\,<\,\tilde{T}_c$ at lower $\tilde{T}_c$. We have also calculated the critical exponents identical with Van der Walls fluid, i.e., same as those obtained before for arbitrary other AdS black holes, which implies that the background clouds of strings do not change the critical exponents.