Discovering the QCD axion with black holes and gravitational waves

Advanced LIGO may be the first experiment to detect gravitational waves. Through superradiance of stellar black holes, it may also be the first experiment to discover the QCD axion with decay constant above the grand unification scale. When an axion's Compton wavelength is comparable to the size of a black hole, the axion binds to the black hole, forming a ``gravitational atom.'' Through the superradiance process, the number of axions occupying the bound levels grows exponentially, extracting energy and angular momentum from the black hole. Axions transitioning between levels of the gravitational atom and axions annihilating to gravitons can produce observable gravitational wave signals. The signals are long…

• NS
  National Science Foundation

  Award: DGE-1147470
• CF
  Concern Foundation
• MZ
  Ministrstvo za Gospodarski Razvoj in Tehnologijo
• ER
  European Research Council

  Award: 228169