Neutrino transport in neutron star merger simulations

Francois Foucart (University of New Hampshire)

The first observation of a neutron star merger through gravitational waves and electromagnetic (EM) signals has shown us the power of multi-messenger observations. Multiple studies based on these observations have placed useful constraints on the equation of state of dense nuclear matter, while the event itself confirmed that mergers are likely (one of) the sources of r-process elements (e.g. gold, uranium) in the Universe. Many interpretations of these observations require reliable models for kilonovae, the radioactively powered EM transient powered by mergers. The numerical simulations that typically inform kilonovae models however have two important “known unknowns’’, namely the uncertainties due to approximate modeling of magnetic fields and neutrinos. In this talk, I will review the role of neutrinos in neutron star-neutron star mergers, as well as existing approximate transport methods used in simulations. I will also present a Monte-Carlo algorithm recently implemented in the SpEC code, used to perform the first simulations of merging neutron stars that directly attempt to solve Boltzmann’s equation of radiation transport. This scheme is purposely built to be as inexpensive as possible: the cost of a simulation remains comparable to simulations using our best existing approximate transport scheme. I will discuss the trade-offs made to reach that target, and how the scheme may be improved in the future. Related papers: arXiv:2103.16588, arXiv:2008.08089

Meeting ID:  854 3210 3337      Password: 959078