Gravitational collider physics

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.

Tidal effects and disruption in superradiant clouds: A numerical investigation

“…These fields can be all or a fraction of DM and may or not couple to standard model fields. In other words, BHs are ideal detectors of ultralight fields [6,13,23].…”

“…Currently, we are unable to probe tidal fields which vary on short timescales: these would lead to "superluminal" motion on the outerpart of our computational domain; as such, we are unable to probe resonances arising from tidal effects. Resonances are interesting on their own [23,27] and might lead to floating or sinking orbits which lead to clear imprints in GW signals [18,20,21,23].…”

“…The existence of superradiant clouds would lead to observable signatures, such as peculiar holes in the massspin plane of BHs [13,14], to monochromatic emission of GWs [14,15] and to a significant stochastic background of GWs [16,17]. The presence of such periodic, nonaxisymmetric structures can leave imprints in planetary and stellar orbits, through Lindblad and co-rotation resonances [18,19], or -of interest for GW astronomythrough floating or sinking orbits [20][21][22][23]. There has been a significant progress in our understanding of the development of the superradiant instabilities [6].…”

“…Here, we focus instead on the effects that a companion star or BH have on the structure of the boson cloud. Tidal effects were studied recently, at an analytical level, and using Newtonian dynamics for non relativistic fields [21][22][23][26][27][28]. The motion of the binary can, at specific orbital frequencies, induce resonant transitions between growing and decaying modes of the boson, that enhance the cloud's depletion and/or transfer energy and angular momentum to the companion through tidal acceleration [29].…”

Efficient computation of galaxy bias with neutrinos and other relics

“…Measurements of N eff both during recombination [3], as well as during big-bang nucleosynthesis (BBN) [4], are in agreement with the ΛCDM prediction of N eff = 3.046 within 10%, thus constraining part of the light-relic parameter space. Likewise, large-scale-structure (LSS) surveys are expected to reach similar sensitivities in N eff [5][6][7].…”