Memory effects in nuclear friction

The status of the problem of describing the dissipative phenomena in nuclear reactions is discussed from experimental and theoretical points of view. Dynamical effects in the initial phase of a fusion reaction are presented showing the evolution of two colliding ¹⁰⁰Mo ions. The role of elastic forces associated with the Fermi surface deformation is shown by comparing the results obtained with and without taking into account the memory effects. The evolution of the unified nuclear system formed after establishing contact between ions is shown to be also strongly influenced by elastic forces associated with the Fermi surface deformations and with related memory effects. Examples are given in which the Fermi surface deformations lead to phenomena usually attributed to the excitation energy and deformation dependence of the friction parameter.