Isovector energy-weighted sums for hot nuclei in presence of relaxation processes

We investigate the collective response function and the energy-weighted sums m_k for isovector mode in hot nuclei. The approach is based on the collisional kinetic theory and takes into consideration the temperature and the relaxation effects. Taking into account a connection between the isovector sound mode and the corresponding surface vibrations we have established the A-dependence of the enhancement factor for the isovector sum rule in a good agreement with experimental data. We have shown that the enhancement factor for the "model independent" sum m_1 is only slightly sensitive to the temperature change.