UAM, Madrid

Thermal Shape Fluctuations in the Description of Hot Nuclei

The behavior of several nuclear properties with temperature is analyzed within the framework of the Finite Temperature Hartree-Fock-Bogolyubov (FTHFB) theory with the Gogny force and large configuration spaces. As representative examples the nuclei $^{164}$Er, $^{152}$Dy and $^{192}$Hg are studied. Numerical results for the superfluid to normal and deformed to spherical shape phase transitions are presented. Thermal shape fluctuations in the quadrupole degree of freedom, around the mean field solution, are taken into account with the Landau prescription. We found a substantial effect of these fluctuations in the average value of several observables, in particular, we get a decrease in the critical temperature ($T_c$) for the shape transition as compared with the plain FTHFB prediction. The new values of ($T_c$) are closer to the ones found in Strutinsky calculations or with the Pairing Plus Quadrupole model Hamiltonian.