Smoking Gun Signatures of Quasilocal Probability in Black Hole Ringdowns

TL;DR

This paper explores how quasilocal probability effects influence black hole ringdowns, proposing observational signatures that can distinguish them from other theories using gravitational wave data.

Contribution

It introduces a set of distinctive, correlated signatures in black hole ringdowns caused by quasilocal probability flux, providing a new way to test quantum gravity effects.

Findings

Identifies three signatures: multi-mode deviations, weak amplitude dependence, waveform damping mismatch.

Shows these signatures are linked to a boundary-flux mechanism and are distinct from modified gravity.

Suggests upcoming gravitational wave observations can detect these effects.

Abstract

Building on recent work introducing the idea of Quasilocal Probability in curved spacetime, we develop its observational implications for black hole ringdown in detail. We show that horizon-induced probability flux leads to an effective non-Hermitian dynamics producing three distinctive signatures, which are correlated multi-mode deviations, weak amplitude dependence and a mismatch between waveform damping and energy accounting. These effects arise from a single boundary-flux mechanism and therefore exhibit a constrained, low-dimensional structure not expected in generic modified gravity scenarios. We demonstrate that while individual deviations may be mimicked, their combined pattern provides a robust discriminator of quasilocal probability. We further argue that upcoming gravitational wave observations can probe these signatures at meaningful precision. We also establish that black hole ringdown is a novel arena to test whether quantum mechanical Hermiticity is really a fundamental property or an emergent symmetry in quantum gravity.