THICKNESS OF THE THERMAL-BOUNDARY SHOCK-WAVE IN THIN AND BULK LIQUID-HE-4 NEAR ABSOLUTE-ZERO TEMPERATURE

Solving the two fluid hydrodynamic equations including dissipation coe fficients, the thickness delta(T) of the thermal boundary shock wave i n thin and bulk liquid He-4 is evaluated explicitly as a function of t emperature via temperature-dependent elementary excitation spectra in the long-wavelength limit and at very low temperatures. The thickness delta(T) in typo and three dimensions does not depend explicitly on an y one of the four second viscosities but only on the thermal conductiv ity kappa(T) and the first viscosity eta(T). At very low temperatures, delta(T) in the thin and the bulk cases has T--6.5 and T-7 dependence s, respectively, which originate from three-phonon processes for both excitation spectra.