Colloquia

Gravitational waves are distortions in the fabric of space and time that are a feature of general relativity, and which were detected one-hundred years after their prediction. The Advanced LIGO and Virgo detectors have observed gravitational waves from nearly one-hundred collisions of black holes and neutron stars, and they are detecting a comparable number during their ongoing observing run. In this talk, I will review the status of these gravitational-wave detections and discuss their implications for understanding fundamental physics through two examples. The first case pertains to the gravitational-wave memory effect: a lasting change in the gravitational-wave strain that is closely connected to the infrared properties of gravitational scattering. LIGO and Virgo will be able to make a statistical measurement of the memory effect towards the end of this decade. I will also discuss new generalizations of the memory effect and their gravitational-wave signatures. The second case relates to using gravitational waves to study dark matter. When a stellar-mass black hole inspirals into a massive black hole surrounded by a high dark-matter density, the dark matter will influence the inspiral of lighter black hole and the gravitational waves emitted from such a binary. I will show how the planned space-based gravitational-wave detector LISA can detect these gravitational waves and measure the presence of dark matter in these binaries.