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Abstract:
We study the impact of a binary companion on black hole superradiance at orbital frequencies away from the gravitational-collider physics (GCP) resonance bands. A superradiant state can couple to a strongly absorptive state via the tidal perturbation of the companion, thereby acquiring a suppressed superradiance rate. Below a critical binary separation, this superradiance rate becomes negative, and the boson cloud gets absorbed by the black hole. This critical binary separation leads to tight constraints on GCP. Especially, a companion with mass ratio q>10^{-3} invalidates all GCP fine structure transitions, as well as almost all Bohr transitions except those from the |211> state. Meanwhile, the backreaction on the companion manifests itself as a torque acting on the binary, producing floating/sinking orbits that can be verified via pulsar timing. In addition, the possible termination of cloud growth may help to alleviate the current bounds on the ultralight boson mass from various null detections.
Biography:
Huiyu Zhu is currently a Ph.D. Candidate at HKUST and will go to IBS for the postdoc position this Fall. Her supervisors are Prof. George Smoot and Prof. Yi Wang. She received her Bachelor degree from SUSTech at 2019 supervised by Prof. Modesto. Her research interest is on cosmology, especially on black hole physics and superradiance.