Comment on Dispersion of Phonons in LiquidHe4

Abstract

The overlap matrix element ($\overrightarrow{\mathrm{k}}+\overrightarrow{\mathrm{l}},\overrightarrow{\mathrm{h}}\left|\mathrm{l}\right|\overrightarrow{\mathrm{k}},\overrightarrow{\mathrm{l}},\overrightarrow{\mathrm{h}}$) which occurs in the theory of phonon dispersion has been evaluated by a completely explicit procedure involving the convolution approximations for the three-, four-, and five-particle distribution functions. The same result is found here by a simpler method involving only the convolution form for the three-particle distribution function.