WoU-MMA: Multiscale Simulations of Neutron Star Mergers

This award supports research in relativity and relativistic astrophysics, and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. Neutron star mergers are one of the most powerful events in the Universe. These events shake the very fabric of spacetime generating so-called gravitational waves that can be detected at distances of hundreds of millions of light years by observatories such as NSF's Laser Interferometric Gravitational-wave Observatory (LIGO). In the extreme conditions found in these events, some of the material inside the neutron stars is transformed into rare elements. Indeed, it is thought that most rare-earth elements, which power all our modern technology, are produced in neutron star mergers. The gravitational wave and light signals from neutron star mergers contain a wealth of information about the physics of matter at extreme densities and the conditions in which these elements are formed. However, their interpretation is complicated by the fact that the motion of plasma in neutron star mergers is very chaotic. This project aims to develop new techniques, inspired by the methodology developed in weather forecasts, to predict the motion of matter in neutron star mergers and its resulting astronomical signals. This project is dedicated to studying the multimessenger emission and the nucleosynthesis yield from neutron star mergers. The team will perform the first "zoom-in" simulations of general-relativistic magnetohydrodynamic turbulence in the hot, dense, nuclear matter formed in mergers. These simulations will be used to develop turbulence models and train machine learning algorithms bridging the scale separation between the neutrino-viscous scale (centimeters) and the disk size (hundreds of kilometers). Global simulations using these new models will be employed to develop uncertainty-quantified models of the gravitational wave and electromagnetic signal from merging neutron stars to interpret past and future observations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.