Comparative study of final state interaction contributions to the dynamic response of quantum fluids

The expression for the final state interaction part of the dynamic response S(q,omega) as given by Silver is derived from a multiple scattering theory. We first discuss the single scattering term which has the same form in the analyses of Silver and Rinat. Next, we indicate the approximations which permit a summation of the full scattering series in the form given by Silver, but we argue that under currently prevailing conditions the approximated sun for S is dominated by the first two terms. In order to determine the better approach, we suggest as a test a comparison of the part of S odd in the variable y.