Self-consistent approach to neutral-current processes in supernova cores.

The problem of neutral-current processes (neutrino scattering, pair emission, pair absorption, axion emission, etc.) in a nuclear medium can be separated into an expression representing the phase space of the weakly interacting probe, and a set of dynamic structure functions of the medium. For a non-relativistic medium we reduce the description to two structure functions SA(ω) and SV (ω) of the energy transfer, representing the axial-vector and vector interactions. SV is well determined by the single-nucleon approximation while SA may be dominated by multiply interacting nucleons. Unless the shape of SA(ω) changes dramatically at high densities, scattering processes always dominate over pair processes for neutrino transport or the emission of right-handed states. Because the emission of right-handed neutrinos and axions is controlled by the same medium response functions, a consistent constraint on their properties from consideration of supernova cooling should use the same structure functions for both neutrino transport and exotic cooling mechanisms.