Gravitational Collider Physics

TL;DR

This paper explores how ultralight particles forming boson clouds around black holes can influence gravitational-wave signals, revealing new physics through resonant transitions and energy transfer effects during binary black hole mergers.

Contribution

It introduces an S-matrix formalism to model cloud transitions and demonstrates how gravitational-wave signals encode information about ultralight particle spectra and interactions.

Findings

Resonant transitions significantly affect gravitational-wave signals.

Long-lived floating orbits and kicks can occur in certain mass ratios.

Waveform analysis can reveal properties of ultralight particles.

Abstract

We study the imprints of new ultralight particles on the gravitational-wave signals emitted by binary black holes. Superradiant instabilities may create large clouds of scalar or vector fields around rotating black holes. The presence of a binary companion then induces transitions between different states of the cloud, which become resonantly enhanced when the orbital frequency matches the energy gap between the states. We find that the time dependence of the orbit significantly impacts the cloud's dynamics during a transition. Following an analogy with particle colliders, we introduce an S-matrix formalism to describe the evolution through multiple resonances. We show that the state of the cloud, as it approaches the merger, carries vital information about its spectrum via time-dependent finite-size effects. Moreover, due to the transfer of energy and angular momentum between the cloud and the orbit, a dephasing of the gravitational-wave signal can occur which is correlated with the positions of the resonances. Notably, for intermediate and extreme mass ratio inspirals, long-lived floating orbits are possible, as well as kicks that yield large eccentricities. Observing these effects, through the precise reconstruction of waveforms, has the potential to unravel the internal structure of the boson clouds, ultimately probing the masses and spins of new particles.