Two-dimensional quantum-corrected black hole in a finite size cavity

TL;DR

This paper investigates quantum corrections to black hole thermodynamics within a finite cavity in a general gravitation-dilaton framework, highlighting the importance of boundary conditions for stability and equilibrium.

Contribution

It introduces a general approach to quantum corrections in gravitation-dilaton theories with finite boundaries, emphasizing the role of boundary conditions in black hole stability.

Findings

Quantum corrections lower the Hawking temperature due to vacuum polarization.

The shell cannot be too close to the horizon for thermal equilibrium.

Finiteness of the system allows defining stable canonical ensembles in certain theories.

Abstract

We consider the gravitation-dilaton theory (not necessarily exactly solvable), whose potentials represent a generic linear combination of an exponential and linear functions of the dilaton. A black hole, arising in such theories, is supposed to be enclosed in a cavity, where it attains thermal equilibrium, whereas outside the cavity the field is in the Boulware state. We calculate quantum corrections to the Hawking temperature $T_{H}$, with the contribution from the boundary taken into account. Vacuum polarization outside the shell tend to cool the system. We find that, for the shell to be in the thermal equilibrium, it cannot be placed too close to the horizon. The quantum corrections to the mass due to vacuum polarization vanish in spite of non-zero quantum stresses. We discuss also the canonical boundary conditions and show that accounting for the finiteness of the system plays a crucial role in some theories (e.g., CGHS), where it enables to define the stable canonical ensemble, whereas consideration in an infinite space would predict instability.