BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Impact of multiple modes on the black-hole superradiant instabilit
 y - Giuseppe Ficarra (King's College London)
DTSTART:20200221T130000Z
DTEND:20200221T140000Z
UID:TALK136267@talks.cam.ac.uk
CONTACT:Nathan Johnson-McDaniel
DESCRIPTION:Ultralight bosonic fields in the mass range $\\sim (10^{-20}-1
 0^{-11})\\\,{\\rm eV}$ can trigger a superradiant instability that extract
 s energy and angular momentum from an astrophysical black hole with mass $
 M\\sim(5\,10^{10})M_\\odot$\, forming a nonspherical\, rotating condensate
  around it. So far\, most studies of the evolution and end-state of the in
 stability have been limited to initial data containing only the fastest gr
 owing superradiant mode. After a brief review of superradiance in flat and
  black-hole spacetimes\, we study the evolution of multimode data in a qua
 si-adiabatic approximation and we show that the dynamics is much richer an
 d depend strongly on the energy of the seed\, on the relative amplitude be
 tween modes\, and on the gravitational coupling. If the seed energy is a f
 ew percent of the black-hole mass\, a black hole surrounded by a mixture o
 f superradiant and nonsuperradiant modes with comparable amplitudes might 
 not undergo a superradiant unstable phase\, depending on the value of the 
 boson mass. If the seed energy is smaller\, as in the case of an instabili
 ty triggered by quantum fluctuations\, the effect of nonsuperradiant modes
  is negligible. We discuss the implications of these findings for current 
 constraints on ultralight fields with electromagnetic and gravitational-wa
 ve observations (arXiv:1812.02758).
LOCATION:Pavilion B Potter Room (B1.19)
END:VEVENT
END:VCALENDAR