Holographic Fractional Order Phase Transitions in CFTs Dual to AdS Black Holes

TL;DR

This paper explores the phase transitions of various AdS black holes in the context of the AdS/CFT correspondence using fractional calculus, revealing nuanced classifications of transition orders that enhance understanding of holographic thermodynamics.

Contribution

It introduces a fractional-order classification scheme for black hole phase transitions, providing a more detailed analysis of critical phenomena in holographic CFTs compared to traditional methods.

Findings

Davies points can be classified into extrema and inflection points.

Transition orders of 3/2 and 4/3 are identified for different black hole solutions.

Fractional calculus offers a refined framework for analyzing phase transitions.

Abstract

In this work, we investigate the CFT phase transitions of various AdS black hole solutions, including the Reissner-Nordstr\"om-AdS (RN-AdS) black hole, the ModMax-AdS black hole, and the RN-AdS black hole formulated within the framework of Kaniadakis statistics, through the lens of the AdS/CFT correspondence. Employing the generalized Ehrenfest classification scheme based on fractional-order derivatives, we analyze the nature of phase transitions at both Davies points and critical points. Davies points, defined as the loci of divergent heat capacity, are typically associated with second-order transitions in the classical Ehrenfest paradigm. However, a refined analysis reveals that these points can be categorized into two distinct types: the first corresponds to extrema in the temperature profile, while the second aligns with its inflection point, i.e., the thermodynamic critical point. Our findings demonstrate that the order of the phase transition is sensitive to this classification, with the first type corresponding to a fractional order of $3/2$, and the second to $4/3$, which is consistent across RN-AdS black holes. Notably, when a specific constraint is imposed, we observe a $3/2$-order phase transition for both the RN-AdS and ModMax-AdS black holes, whereas in the case of the RN-AdS black hole with Kaniadakis statistics, two critical points arise under constrained paths, each exhibiting a transition of order $4/3$. This generalized, fractional-order framework enables a more precise and discriminating characterization of CFT phase transitions in holographic settings, revealing distinctions that remain hidden under traditional classifications. The results provide deeper insight into the rich structure of black hole thermodynamics on the CFT side and highlight the significance of fractional calculus as a powerful tool for probing critical phenomena within the AdS/CFT framework.