Please contact lukas.graf@berkeley.edu or jeffberryman@berkeley.edu for zoom links.

The growing gravitational wave dataset makes black hole population studies possible. In this talk I will demonstrate how such studies can be used to study particle and nuclear physics. The key insight is that a wide range of initial stellar masses leave no compact remnant, due to the physics of pair-instability; the unpopulated space in the stellar graveyard is known as the black hole mass gap (BHMG). New physics can dramatically alter the late stages of stellar evolution and shift the BHMG, when it acts as an additional source of energy (loss) or modifies the equation of state. The latter will be the focus of this talk, in which I will show some new results with axions in the so-called cosmic triangle. I will also demonstrate how these predictions can be tested with the gravitational wave observations by the LIGO/Virgo/Kagra collaboration, and what we can already infer from GWTC-2 and 3.