Tidal effects and disruption in superradiant clouds: A numerical investigation
Vítor Cardoso, Francisco Duque, Taishi Ikeda
Abstract
The existence of light, fundamental bosonic fields is an attractive possibility that can be tested via black hole observations. We study the effect of a tidal field---caused by a companion star or black hole---on the evolution of superradiant scalar-field states around spinning black holes. For small tidal fields, the superradiant ``cloud'' puffs up by transitioning to excited states and acquires a new spatial distribution through transitions to higher multipoles, establishing new equilibrium configurations. For large tidal fields, the scalar condensates are disrupted; we determine numerically the critical tidal moments for this to happen and find good agreement with Newtonian estimates. We show that the impact of tides can be relevant for known black hole systems such as the one at the center of our Galaxy or the Cygnus X-1 system. The companion of Cygnus X-1, for example, will disrupt possible scalar structures around the black hole for gravitational couplings as large as $M\ensuremath{\mu}\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$.