IPA Colloquium FS25

Thursday 30 Oct 2025, 12:00 → 13:00 Europe/Zurich

32/1-A24 (CERN)

12:05 → 13:00 Talk

12:05 Probing the Black-Hole Spectrum with Gravitational Waves

Over the last ten years, gravitational-wave observations have begun to reveal black holes across their astrophysical mass spectrum, from stellar remnants to the giants anchoring galaxies. The growing LIGO–Virgo–KAGRA catalog has transformed our view of stellar-mass black holes, uncovering unexpected diversity in their masses, spins, and merger rates. Population modeling of these events is beginning to constrain their formation channels and evolutionary histories. At the opposite extreme, pulsar timing arrays have detected a nanohertz gravitational-wave background consistent with a population of inspiraling supermassive black hole binaries, marking the first direct probe of black hole growth through galaxy mergers. The forthcoming LISA mission will bridge these regimes by observing mergers of massive black holes at high redshift and extreme mass-ratio inspirals that trace strong-field gravity around individual horizons. Together, these observatories will transform the gravitational-wave spectrum—from hertz to nanohertz—into a map of black hole evolution across cosmic time. I discuss this evolving picture and present some of the research threads within the ETHZ gravitational physics group.

Speaker: Michele Vallisneri (ETH Zurich)