10-05U

Formalism of perturbation theory is developed and used for calculations of perturbation theory corrections to generalized collective modes, that are caused by the cross-correlations of heat and viscoelastic dynamic processes in pure and complex liquids. General form of such theory is formulated up to the second order including. This theory is verified for the cases of simples dynamic models of liquids, and obtained results are analyzed in comparison with known results. This shown that under appropriate conditions the results of perturbation theory allow us to reproduce the results know for this models.