Curvature and dynamical spacetimes: can we peer into the quantum regime?

TL;DR

This paper investigates whether dynamical astrophysical events like black hole mergers can reach curvature levels where quantum gravity effects become significant, finding that such events generally do not produce sufficiently high curvature to probe the quantum regime.

Contribution

The study quantifies curvature increases during dynamical spacetime events, showing they are generally insufficient to access quantum gravitational effects without fine-tuning.

Findings

Dynamical black hole mergers increase curvature modestly (~3 times)

Scalar field collapse can cause large curvature peaks, but still below quantum gravity thresholds

Typical astrophysical processes do not reach the curvature needed for quantum regime exploration

Abstract

Stationary compact astrophysical objects such as black holes and neutron stars behave as classical systems from the gravitational point of view. Their (observable) curvature is everywhere "small". Here we investigate whether mergers of such objects, or other strongly dynamical spacetimes such as collapsing configurations, may probe the strong-curvature regime of General Relativity. Our results indicate that dynamical black hole spacetimes always result in a modest increase $\sim 3$ in the Kretschmann scalar, relative to the stationary state. Our results show that the Kretschmann scalar can dynamically increase by orders of magnitude, during the gravitational collapse of scalar fields, and that the (normalized) peak curvature does not correspond to that of the critical solution. Nevertheless, without fine tuning of initial data, this increase lies far below that needed to render quantum-gravity corrections important.