Best Approximation to a Reversible Process in Black-Hole Physics and the Area Spectrum of Spherical Black Holes

TL;DR

This paper investigates the minimal area increase of Reissner-Nordström black holes when absorbing the lightest charged particles, supporting a universal, evenly spaced area spectrum consistent with quantum gravity predictions.

Contribution

It demonstrates that the minimal area increase is smaller for charged particles, providing evidence for a universal, evenly spaced black hole area spectrum.

Findings

Minimal area increase is $4 \hbar$, smaller than for neutral particles.

Supports a universally spaced area spectrum for spherical black holes.

Aligns with predictions by Mukhanov, Bekenstein, and Hod.

Abstract

The assimilation of a quantum (finite size) particle by a Reissner-Nordstr\"om black hole inevitably involves an increase in the black-hole surface area. It is shown that this increase can be minimized if one considers the capture of the lightest charged particle in nature. The unavoidable area increase is attributed to two physical reasons: the Heisenberg quantum uncertainty principle and a Schwinger-type charge emission (vacuum polarization). The fundamental lower bound on the area increase is $4 \hbar$, which is smaller than the value given by Bekenstein for neutral particles. Thus, this process is a better approximation to a reversible process in black-hole physics. The universality of the minimal area increase is a further evidence in favor of a uniformly spaced area spectrum for spherical quantum black holes. Moreover, this universal value is in excellent agreement with the area spacing predicted by Mukhanov and Bekenstein and independently by Hod.