Viscosity coefficients of normal fluid and oscillatory motion in bulk liquid helium at low temperatures

The viscosity coefficients and the penetration depth of a viscous wave in bulk liquid helium at low temperatures are evaluated explicitly as functions of temperature, including the effects of three-phonon processes originating from the anomalous excitation spectrum. Based on these results, the laminar drag exerted by liquid helium on an oscillating microsphere and the temperature variation of the energy dissipation of the oscillating plate are discussed.