Near-horizon microstructure and superradiant instability of black holes
  Ultralight bosons, as important candidates of dark matter, can condense
around spinning black holes (BHs) to form long-lived ``boson clouds'' due to
superradiance instability. The boson-BH system can be observed through
gravitational wave detection and may become a new window to find traces of
ultralight bosons. In this letter we explore the effects on the superradiant
instability of BHs from the near-horizon microstructure. By introducing the
reflection parameter near a BH horizon, we derived analytical results on the
corrections to both energy levels of bosonic cloud and its characteristic
frequencies of superradiance instability. Our results imply that the evolution
of a boson-BH system and gravitational waves it emits would be influenced by
the near-horizon physics of a BH.
