Nuclear Theory Department

(Head – Professor V. M. Kolomietz)

 Main directions of scientific activity: 

·        Investigation of macroscopic collective motion and equation of state in nuclei at finite temperatures to find out novel features of a finite Fermi liquid at high pressure and non-equilibrium value of the particle density.

·        Investigation of the memory effects influence and the relaxation processes on the nuclear collective motion at large amplitude and the multipole giant resonances.

·        Application of the theory developed earlier in nuclear theory department to the calculations of the transport characteristics of collective motion, in particular of stiffness, inertia and friction coefficients, and the description of the fission process of heavy nuclei using these coefficients.

·        Study of dynamics of the phase transitions and the expansion of volume instability in excited nuclei for applications to the multifragmentation of nuclei in heavy ion collisions. 

The most important scientific results: 

·        Theory of boiling (cavitation) of overheated asymmetric nuclear Fermi liquid has been developed. The conditions of growing of volume instability and the dependence of the critical size of vapor phase on the parameter of isotopic asymmetry for overheated nuclear matter have been established.

·        Theory of collective motion in the nuclei including memory effects was proposed. The theory was applied to the simultaneous description of the widths of giant multipole resonances and the dynamics of the descent from saddle- to scission point.

·        Dependence of the fission fragments kinetic energy on the nucleon number has been calculated for the transuranium nuclei. The obtained results are in a good agreement with the experimental data.

·        Theory of the splitting of the isovector giant resonances in near-spherical heavy nuclei was developed within the asymmetric Fermi liquid theory (Landau-Vlasov kinetic theory) with macroscopic boundary conditions. It was found that the dependence of the splitting effect is linear with respect to the asymmetric parameter and the isovector interaction constants, such as the Landau parameter in volume of nucleus and the surface tension constant.

·        Simple analytical expressions for the temperature dependence of the kinetic coefficients which determine the decay width of heavy nuclei have been proposed. These expressions are based on the analysis of the kinetic coefficients calculated within the linear response theory and the locally oscillator approximation with realistic potentials for the mean field of deformed nuclei.

·        Kinetic semiclassical theory of the collective excitations in finite Fermi systems including the dynamical surface effects has been developed. It was shown that taking into account a coupling between the motion of nucleons and surface vibrations the unified description of the isoscalar giant resonances and the low-lying collective modes in nuclei is achieved.

·        Microscopic theory of friction coefficients that describes the transform of the collective energy into the energy of the chaotic nucleon motion was suggested. Friction coefficients have been calculated for the heavy and the superheavy nuclei along on the fission path. It has been found that due to the dynamical correlations between successive reflections of a nucleon on the surface of the nucleus, the friction coefficient contributes only about 20 - 30 % to the commonly used wall formula.