# Nils Deppe

## Assistant Professor

### Overview

My group studies extreme matter and gravity by solving Einstein's equations of general relativity using massively parallel computer simulations, a field called "numerical relativity." We simulate mergers of binary black holes, neutron stars, and black hole-neutron stars within the Simulating eXtreme Spacetimes (SXS) collaboration. We also study turbulence and instabilities in rotating stars and core-collapse supernovae simulations with collaborator Michael Pajkos. We produce accurate gravitational waveforms for calibrating models used by observers like LIGO, Virgo, and KAGRA to analyze their (noisy) data. Since we only have one universe, simulations provide a way to experiment with different input physics and compare the results with observations to understand the laws of our universe at its most extreme.

**About SXS**

SXS develops and uses the Spectral Einstein Code (SpEC) for our current production simulations. We are also developing SpECTRE, a next-generation multi-physics code aimed at improving a number of algorithmic and computational challenges SpEC faces. For example, SpECTRE scales to larger core counts, has improved magnetohydrodynamics, and dynamically adjusts the way equations are solved for optimal efficiency. Our goal is to use SpECTRE to create a catalog of highly accurate binary neutron star and binary black hole-neutron star waveforms, which, among other things, constrains the equation of state of dense matter, probes populations of stars in the universe, and provides and independent way of measuring the expansion of the universe.