Emergence of product of constant curvature spaces in loop quantum cosmology

TL;DR

This paper investigates how loop quantum cosmology modifies the interior structure of black holes, leading to emergent product spaces of constant curvature that resemble charged Nariai and Bertotti-Robinson spacetimes with quantum-originated electromagnetic fields.

Contribution

It demonstrates that loop quantum effects produce asymptotic spacetimes as products of constant curvature spaces, resembling charged Nariai and anti Bertotti-Robinson solutions, with emergent cosmological constants.

Findings

Quantum effects resolve singularities and produce non-singular bounces.

Asymptotic spacetimes are products of constant curvature spaces with high curvature.

Emergent effective metrics satisfy Einstein's equations with quantum-originated energy-momentum tensors.

Abstract

The loop quantum dynamics of Kantowski-Sachs spacetime and the interior of higher genus black hole spacetimes with a cosmological constant has some peculiar features not shared by various other spacetimes in loop quantum cosmology. As in the other cases, though the quantum geometric effects resolve the physical singularity and result in a non-singular bounce, after the bounce a spacetime with small spacetime curvature does not emerge in either the subsequent backward or the forward evolution. Rather, in the asymptotic limit the spacetime manifold is a product of two constant curvature spaces. Interestingly, though the spacetime curvature of these asymptotic spacetimes is very high, their effective metric is a solution to the Einstein's field equations. Analysis of the components of the Ricci tensor shows that after the singularity resolution, the Kantowski-Sachs spacetime leads to an effective metric which can be interpreted as the `charged' Nariai, while the higher genus black hole interior can similarly be interpreted as anti Bertotti-Robinson spacetime with a cosmological constant. These spacetimes are `charged' in the sense that the energy momentum tensor that satisfies the Einstein's field equations is formally the same as the one for the uniform electromagnetic field, albeit it has a purely quantum geometric origin. The asymptotic spacetimes also have an emergent cosmological constant which is different in magnitude, and sometimes even its sign, from the cosmological constant in the Kantowski-Sachs and the interior of higher genus black hole metrics. With a fine tuning of the latter cosmological constant, we show that `uncharged' Nariai, and anti Bertotti-Robinson spacetimes with a vanishing emergent cosmological constant can also be obtained.