  We generalize our virial approach to study spin-polarized neutron matter and
the consistent neutrino response at low densities. In the long-wavelength
limit, the virial expansion makes model-independent predictions for the density
and spin response, based only on nucleon-nucleon scattering data. Our results
for the neutrino response provide constraints for random-phase approximation or
other model calculations, and we compare the virial vector and axial response
to response functions used in supernova simulations. The virial expansion is
suitable to describe matter near the supernova neutrinosphere, and this work
extends the virial equation of state to predict neutrino interactions in
neutron matter.

Nuclear Theory;Astrophysics