THERMAL-CONDUCTIVITY AND VISCOSITY IN DILUTE HE-3-HE-4 MIXTURES BELOW0.6 K

The effects of three-phonon processes on the phonon thermal conductivi ty and phonon viscosity in dilute He-3-He-4 mixtures below 0.6 K are i nvestigated The characteristic scattering times for phonon-phonon inte raction-limited thermal conductivity and viscosity are calculated from a collision matrix which contains information on the three-phonon pro cesses. We find that die to phonon-He-3 interactions the phonon moment um range in which three-phonon processes occur is reduced in compariso n with that of the pure He-4 case. Results for thermal conductivity an d viscosity show good agreement with experimental data without having to adjust the rates of phonon absorption by He-3 and the tares of elas tic scattering of phonons with He-3.