  We derive a kinetic equation for chiral matter at non-zero chemical potential
that governs the response of the parity odd part of the distribution function
to perturbations of the Robertson-Walker metric. The derivation is based on a
recent evaluation of the gravitational polarization tensor at non-zero chemical
potential. We also provide the equations for gravity waves that follow from the
anisotropic stress tensor describing the lepton asymmetry. These equations can
be used to assess the effects that a non-zero neutrino chemical potential would
have on the evolution of cosmological perturbations.
