Comment on "Quantum-Mechanical Suppression of Gas Accretion by Primordial Black Holes"

TL;DR

This paper critiques a recent claim that quantum effects suppress gas accretion onto primordial black holes, clarifying that no such suppression occurs when considering realistic accretion rates.

Contribution

It refutes prior assertions by showing that quantum effects do not inhibit accretion rates for primordial black holes.

Findings

No suppression of accretion rate per atom for the black holes considered.

Quantum effects do not significantly alter gas accretion onto primordial black holes.

The original claim was based on an oversimplified single-atom model.

Abstract

It was recently claimed (arXiv:2409.09081v1 [astro-ph.HE]) that accretion of ordinary matter on black holes of mass $(6\times 10^{14}-4\times10^{19})\,$g would be inhibited by quantum mechanical effects, namely the de Broglie wavelength of the electron being larger than the Schwarzschild radius. However the conclusion is based on considering accretion of a single atom over the age of the Universe. There is no suppression of the accretion rate per atom on such black holes.