In 2015 we witnessed a revolution: the first direct observation of a gravitational-wave (GW) sourced by a binary black hole coalescence. Since then we have observed roughly a hundred GW events, establishing GW astronomy as a new field in physics. For millennia we have used electromagnetic waves (from stars to the CMB) to build most of our knowledge about the Universe, now GWs promise to give us access to the most violent events happening in the most extreme regions of spacetime -- the surroundings of compact objects, like black holes. In particular, a plethora of interesting phenomena is expected to happen in strong gravity regions if some light boson (with a de Broglie wavelength of the order of the spacetime curvature length-scale) exists in nature, effectively allowing us to use black holes as particle detectors. These light bosons are ubiquitous in extensions of the Standard Model and, in particular, they can be a (wave) dark matter candidate [like the QCD axion or an axion-like-particle (ALP)]. In this pizza seminar I will explain some of these exciting ideas on how to use black holes and compact binaries as particle detectors and discuss some current constraints.
Elia Bertoldo, Clara Fernández, Giada Caneva