Rainbow Black Hole From Quantum Gravitational Collapse

TL;DR

This paper explores how quantum gravitational effects modify the collapse of a dust ball into a black hole, leading to a rainbow black hole with mode-dependent properties and observable chromatic aberration in gravitational lensing.

Contribution

It introduces a mode-dependent dressed geometry during gravitational collapse, revealing quantum effects that replace singularities with bounces and produce rainbow black holes.

Findings

Quantum effects resolve classical singularity with a bounce.

Backreaction accelerates the bounce compared to dust-only collapse.

Mode dependence causes chromatic aberration in gravitational lensing.

Abstract

Quantum evolution of a scalar field's modes propagating on quantum spacetime of a collapsing homogeneous dust ball is written effectively, as an evolution of the same quantum modes on a (semiclassical) dressed geometry. When the backreaction of the field is discarded, the classical spacetime singularity is resolved due to quantum gravity effects and is replaced by a quantum bounce on the dressed collapse background. In the presence of backreaction, the emergent (interior) dressed geometry becomes mode dependent and the energy density associated with the backreaction of each mode scales as a radiation fluid. Semiclassical dynamics of this so-called {\em rainbow} dressed background is analyzed. It turns out that the backreaction effects speed up the occurrence of the bounce in comparison to the case where only a dust fluid is present. By matching the interior and exterior regions at the boundary of dust, a mode-dependent black hole geometry emerges as the exterior spacetime. Properties of such a rainbow black hole are discussed. That mode dependence causes, in particular, a chromatic aberration in the gravitational lensing process of which maximal magnitude is estimated via calculation of the so-called Einstein angle.