Field Theoretical Quantum Effects on the Kerr Geometry

TL;DR

This paper investigates quantum effects on the Kerr black hole within a specialized gravity model, revealing stability in the outer region but significant changes in the inner geometry due to quantum renormalization.

Contribution

It formulates Einstein gravity with symmetries as a nonlinear sigma-model and computes its beta functions to all orders, applying this to analyze quantum modifications of the Kerr geometry.

Findings

Outer region of Kerr remains stable under quantum effects.

Inner geometry of Kerr experiences significant quantum-induced changes.

Beta functions are derived to all orders, indicating the model's renormalization behavior.

Abstract

We study quantum aspects of the Einstein gravity with one time-like and one space-like Killing vector commuting with each other. The theory is formulated as a $\coset$ nonlinear $\sigma$-model coupled to gravity. The quantum analysis of the nonlinear $\sigma$-model part, which includes all the dynamical degrees of freedom, can be carried out in a parallel way to ordinary nonlinear $\sigma$-models in spite of the existence of an unusual coupling. This means that we can investigate consistently the quantum properties of the Einstein gravity, though we are limited to the fluctuations depending only on two coordinates. We find the forms of the beta functions to all orders up to numerical coefficients. Finally we consider the quantum effects of the renormalization on the Kerr black hole as an example. It turns out that the asymptotically flat region remains intact and stable, while, in a certain approximation, it is shown that the inner geometry changes considerably however small the quantum effects may be.