Анотація:
We discuss a number of unusual phenomena, which have been discovered recently in anisotropic
quasiparticle systems in superfluid ⁴He. These include the creation of high-energy phonons by a pulse of
low-energy phonons, the suprathermal distribution of high-energy phonons in long phonon pulses, the mesa
shape of the angular distribution of low-energy phonons, the creation of a «hot line» when two-phonon
pulses cross. The thermodynamic properties of anisotropic quasiparticle systems of He II are derived for all
degrees of anisotropy.