Colliding black holes might soon prove that one of the most fundamental laws of quantum mechanics is actually an illusion.
April 26, 2026
Original Paper
Smoking Gun Signatures of Quasilocal Probability in Black Hole Ringdowns
arXiv · 2604.20922
The Takeaway
Hermiticity is a core rule in quantum mechanics that ensures probabilities always add up to 100%. This paper identifies three specific signals in the gravitational waves of black hole ringdowns that could disprove this rule. If these signals are detected, it would show that Hermiticity is just an emergent property rather than a fundamental law of nature. This would mean that at the most extreme levels of gravity, the standard rules of quantum physics break down. We can now test this by listening to the vibrations of black holes as they merge. This discovery could force us to rewrite every quantum textbook in existence.
From the 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 there