Dirac clouds around dilatonic black holes

TL;DR

This paper introduces a new mechanism supporting Dirac clouds around extremal dilatonic black holes, independent of superradiance, revealing their potential particle-like behavior.

Contribution

It discovers a novel, superradiance-independent mechanism for Dirac clouds and analyzes their energy spectrum around extremal dilatonic black holes.

Findings

Dirac clouds supported by a new mechanism in dilatonic gravity

Bound states become real at extremal black holes

Extreme dilatonic black holes behave as elementary particles

Abstract

Dirac cloud is in absence in general relativity since the superradiance mechanism fails to work for Dirac fields. For the first time we find a novel mechanism to support Dirac clouds, which is independent on superradiance mechanism. We study quasi bound states of Dirac particles around a charged spherical black hole in dilatonic gravity. We find that the quasi bound states become real bound states when the central black hole becomes extremal. We make an intensive study of the energy spectrum of the stationary clouds for different fine structure constant $\mu M$, and reveal the existence condition of these clouds. Our result strongly implies that extreme dilatonic black holes behave as elementary particles.