Title: GENERALIZED COLLECTIVE MODES APPROACH: MODE CONTRIBUTIONS TO TIME CORRELATION FUNCTIONS IN LIQUID LEAD
Authors: T.Bryk (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 79011 Lviv, Ukraine; Department of Chemistry, University of Houston, Houston, TX 77004, USA), I.Mryglod (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 79011 Lviv, Ukraine)

Contributions of different collective excitations to the density-density and heat-heat time correlation functions in pure liquids are studied within an approach of generalized collective modes. It is shown, that a kinetic relaxing mode, caused by slow density fluctuations, defines almost completely the shape of density-density time correlation function for wavenumbers close to the main peak position of the static structure factor. Analytical three-variable model is used to explain negative amplitudes of contributions to dynamical structure factor from short-wavelength excitations. Such contributions can appear in the range of wavenumbers close to the main peak position of static structure factor.

Key words: hydrodynamics, time correlation functions, collective excitations, liquids, mode contribution
PACS: 05.20.Jj, 61.20.Lc, 61.25.Mv