The problem of the creation of high-energy phonons (h-phonons) by a pulse of low-energy phonons (l-phonons) moving from a heater to a detector in superfluid helium, is solved. The rate of h-phonon creation is obtained ...

The analytical relation for the rate of one phonon decay into three is obtained. Starting from the relation obtained, the rate of spontaneous decay in the first order of perturbation theory is found. It is shown, that ...

Starting from the kinetic equation for phonons in superfluid helium, expressions for the rates of three-phonon scattering in isotropic and anisotropic phonon systems were obtained for different pressures. These expressions ...