On the possibility of exciting zero sound in He3 at speeds below the Fermi speed
Demikhovskii V. Ya., Maksimova G. M.
It is shown that a large-amplitude wave can propagate in a Fermi liquid at a speed that is less than the Fermi speed. The collisionless damping in this case is proportional to the small parameter a = (ω0τ)~ι.