Neutrino processes in partially degenerate neutron matter

TL;DR

This paper extends the understanding of neutrino interactions in partially degenerate neutron matter during supernovae, deriving new expressions for the spin structure factor and showing nondegenerate approximations are valid in most conditions.

Contribution

It provides new formulas for the spin structure factor in neutron matter and compares spin relaxation rates from different interaction models, improving supernova neutrino process modeling.

Findings

Spin relaxation rates are about half of those predicted by one-pion-exchange models.

Nondegenerate limit approximations are valid for most post-bounce supernova conditions.

Chiral effective field theory yields more accurate neutrino process rates.

Abstract

We investigate neutrino processes for conditions reached in simulations of core-collapse supernovae. Where neutrino-matter interactions play an important role, matter is partially degenerate, and we extend earlier work that addressed the degenerate regime. We derive expressions for the spin structure factor in neutron matter, which is a key quantity required for evaluating rates of neutrino processes. We show that, for essentially all conditions encountered in the post-bounce phase of core-collapse supernovae, it is a very good approximation to calculate the spin relaxation rates in the nondegenerate limit. We calculate spin relaxation rates based on chiral effective field theory interactions and find that they are typically a factor of two smaller than those obtained using the standard one-pion-exchange interaction alone.