Speaker
Description
Isospin-equilibrating weak processes, called Urca" processes, are of fundamental importance in astrophysical environments like proto-neutron stars, neutron star mergers, and supernovae. In these environments, matter can reach high temperatures of in the MeV range and be subject to large magnetic fields. Previous studies on the effect of magnetic fields on isospin-equilibration processes relied on the Fermi surface approximation, which is not a reliable approximation in the neutrino-transparent regime of matter in supernovae or neutron star mergers. In a recent study, we went beyond the Fermi surface approximation, performing the full phase space integral to obtain direct Urca rates in a background magnetic field. We extend these calculations to incorporate the collisional broadening (modified Urca'') contribution. We use the recently developed Nucleon Width Approximation, naturally incorporating the magnetic field dependence of contributions from both direct Urca and modified Urca processes. We demonstrate the impact of magnetic fields on the isospin-equilibrium condition for two finite-temperature equations of state with different direct Urca thresholds. We also study the impact of magnetic fields on the bulk viscous dissipation of density oscillations relevant in postmerger scenarios.
