Speaker
Description
The mergers we observe with LIGO and Virgo are ultimately driven by the emission of energy and angular momentum via gravitational waves. However, relativity alone is not sufficient to explain how compact objects pair and merge. For instance, black-hole binaries of ~10Msun orbiting at separations >~10Rsun will take more than a Hubble time to merge under gravitational radiation reaction. Additional mechanisms of astrophysical nature are needed to explain the LIGO/Virgo events. Conceiving plausible scenarios for the formation and evolution of binary black holes is a major industry in the field and still presents considerable challenges. But challenges reveal opportunities for discovery! I present an update on the formation-channel problem in gravitational-wave astronomy with a specific focus on hierarchical black-hole mergers. These provide, in my opinion, an orthogonal, but at the same time complementary, direction to the usual “field vs clusters” debate.
