Quantization of area for event and Cauchy horizons of the Kerr-Newman black hole

TL;DR

This paper critically examines the idea that black hole horizon areas are quantized in specific integer-based patterns, highlighting physical constraints and limitations in applying such proposals to Kerr-Newman black holes.

Contribution

It provides a detailed analysis of the physical constraints on horizon area quantization proposals, especially in the context of Kerr-Newman black holes, challenging some string-inspired theories.

Findings

Integer-based quantization proposals often fail for Kerr-Newman black holes.

Physical constraints limit the applicability of certain horizon area quantization models.

Explicit spectra calculations suggest caution in assuming universal quantization patterns.

Abstract

Based on various string theoretic constructions, and various string-inspired generalizations thereof, there have been repeated suggestions that the areas of black hole event horizons might be quantized in a quite specific manner, in terms of linear combinations of square roots of positive integers. It is important to realise that there are significant physical constraints on such integer-based proposals when one (somewhat speculatively) attempts to extend them outside their original extremal and supersymmetric framework. Specifically, in their most natural and direct physical interpretations, some of the more speculative integer-based proposals for the quantization of horizon areas fail for the ordinary Kerr-Newman black holes in (3+1) dimensions, essentially because the fine structure constant is not an integer. A more baroque interpretation involves asserting the fine structure constant is the square root of a rational number; but such a proposal has its own problems. Insofar as one takes (3+1) general relativity (plus the usual quantization of angular momentum and electric charge) as being paramount, the known explicitly calculable spectra of horizon areas for the physically compelling Kerr-Newman spacetimes indicate that some caution is called for when assessing the universality of some of the more speculative integer-based string-inspired proposals.