Zero sound in triplet-correlated superfluid neutron matter

Abstract

The linear response of a superfluid neutron liquid onto external vector field is studied for the case of $^{3}P_{2}-\,^{3}F_{2}$ pairing. The consideration is limited to the case when the wave-length of the perturbation is large as compared to the coherence length in the superfluid matter and the transferred energy is small in comparison with the gap amplitude. The obtained results are used to analyse the collisionless phonon-like excitations of the condensate of superfluid neutrons. In particular, we analyze the case of neutron condensation into the state with $m_{j}=0$ which is conventionally considered as the preferable one in the bulk matter of neutron stars. Zero sound (if it exists) is found to be anisotropic and undergoes strong decrement below some temperature threshold depending substantially on the intensity of Fermi-liquid interactions.