Euclidean methods and phase transitions for the strongest deformations compatible with Schwarzschild asymptotics

TL;DR

This paper explores the thermodynamics and phase transitions of a regular black hole model with significant subleading corrections to Schwarzschild behavior, revealing unique temperature and phase structure features in various spacetimes.

Contribution

It introduces a detailed thermodynamic analysis of a regular black hole with strong corrections, deriving new quantities and examining phase behavior in different cosmological backgrounds.

Findings

Regularization prevents Hawking-Page transition.

Effective temperature differs from surface gravity temperature.

Deviations from universal critical ratios observed.

Abstract

In this paper, we investigate the thermodynamic properties of a regular black hole model which exhibits the most significant subleading corrections to the Schwarzchild asymptotic behavior, in the context of general relativity, using the Euclidean path integral approach. We review the derivation of the Lagrangian for the matter fields which act as a source for this geometry, explicitly derive the proper thermodynamic quantities introduced in the first law of black hole mechanics, and show that they satisfy the Smarr formula. This analysis naturally leads to the emergence of an effective temperature that is distinct from the one associated with surface gravity. Furthermore, we study the phase structure in anti-de Sitter, Minkowski, and de Sitter spacetimes in the canonical ensemble, considering this effective temperature as the appropriate choice. We show that in this case the regularization of the singularity prevents the Hawking-Page transition and also leads to a deviation from the ``universal" mean-field theory critical ratio. We conjecture that the way a singularity is rendered smooth plays a pivotal role to the degree of this deviation. Finally, we provide remarks on constraints imposed on the minimal length scale by observational data and the viability of regular black holes.