Uncovering the dynamics of black holes and neutron stars for gravitational wave and multimessenger astronomy

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With the stunning observations of gravitational waves from merging black holes and neutron stars made recently by LIGO/Virgo, we have entered a new age of multimessenger astronomy. There is every indication that as the number and sensitivity of gravitational wave detectors increase in the coming years, that there will be a flood of observations, revealing new aspects of the universe visible only in gravitational waves. However, maximizing the return of these observations, and utilizing them as a new probe of fundamental physics will require advances in our theoretical understanding of gravity in this regime. A central part of this proposal is to study neutron star mergers--the violent collision of the densest stars in the Universe--with the ultimate goal of understanding the gravitational wave signal, and accompanying electromagnetic transients, in order to aid in targeting and interpreting current and future observations. As part of achieving this long-term goal, my team and I will study several aspects of these systems that remain poorly understood, including the effects of neutron star spin and orbital eccentricity, and the dynamics of the post-merger remnant and accretion disk, and determine how they can shed light on the behavior of nuclear matter at the highest densities, the origin of the heaviest elements in the universe, and other questions. My team and I will study the underlying mechanisms of relativistic black hole jets that govern accreting black hole systems of all sizes, from those arising from neutron star mergers, to those residing at the centers of galaxies. We will elucidate the role of a spinning black hole's geometry, and large reservoir of rotational energy, in powering jets, both in stationary and dynamical scenarios. This will involve bridging the divide between different descriptions of the plasma dynamics to include the effects of both the black hole spacetime, as well as particle effects like acceleration and heating. My team and I will also explore how this new window into extreme gravity can be used to look for new fundamental physics, such as the origin of dark matter. We will determine how gravitational wave observations can be used to probe the existence of new particles through superradiance, a process which causes black holes to form clouds of ultralight bosons at the expense of their rotational energy. We will also study how neutron stars could be converted into black holes in some models of dark matter, and understanding the observational signatures. This research will provide students with the chance to participate in a rapidly growing field, gaining fluency in a number of topics including astrophysics, gravity, particle physics, and computational physics. They will develop skills in advanced mathematics, software development, and high-performance computing that are increasingly in demand both in academia and areas of technology like data science.