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. 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. Consideration is limited to the case when the wavelength of a 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 analyze collisionless soundlike excitations of the superfluid condensate. Zero sound (if it exists) is found to be anisotropic and undergoes a strong decrement below some temperature threshold depending substantially on the intensity of Fermi-liquid interactions.

• Received 15 January 2011

DOI:https://doi.org/10.1103/PhysRevC.83.055803