Space-Time Structure of Loop Quantum Black Hole

TL;DR

This paper improves the semiclassical analysis of loop quantum black holes by modifying the Hamiltonian constraint, revealing regular metrics with bounded curvature, and exploring their causal structure and thermodynamics.

Contribution

It introduces a simple modification to the quantum constraint that yields a class of semiclassical solutions, including a regular black hole metric with correct asymptotic behavior.

Findings

The semiclassical metric is regular at r=0 with maximum curvature at Planck scale.

The solution interpolates between two flat regions, describing a non-singular black hole.

Thermodynamic properties like temperature and entropy are well-defined and regular.

Abstract

In this paper we have improved the semiclassical analysis of loop quantum black hole (LQBH) in the conservative approach of constant polymeric parameter. In particular we have focused our attention on the space-time structure. We have introduced a very simple modification of the spherically symmetric Hamiltonian constraint in its holonomic version. The new quantum constraint reduces to the classical constraint when the polymeric parameter goes to zero.Using this modification we have obtained a large class of semiclassical solutions parametrized by a generic function of the polymeric parameter. We have found that only a particular choice of this function reproduces the black hole solution with the correct asymptotic flat limit. In r=0 the semiclassical metric is regular and the Kretschmann invariant has a maximum peaked in L-Planck. The radial position of the pick does not depend on the black hole mass and the polymeric parameter. The semiclassical solution is very similar to the Reissner-Nordstrom metric. We have constructed the Carter-Penrose diagrams explicitly, giving a causal description of the space-time and its maximal extension. The LQBH metric interpolates between two asymptotically flat regions, the r to infinity region and the r to 0 region. We have studied the thermodynamics of the semiclassical solution. The temperature, entropy and the evaporation process are regular and could be defined independently from the polymeric parameter. We have studied the particular metric when the polymeric parameter goes towards to zero. This metric is regular in r=0 and has only one event horizon in r = 2m. The Kretschmann invariant maximum depends only on L-Planck. The polymeric parameter does not play any role in the black hole singularity resolution. The thermodynamics is the same.