APPROXIMATE PARTICLE NUMBER PROJECTION FOR FINITE-RANGE DENSITY-DEPENDENT FORCES

The Lipkin-Nogami method is generalized to deal with finite range dens ity dependent forces. New expressions are derived and realistic calcul ations with the Gogny force are performed for the nuclei Er-164 and Er -168. The sharp phase transition predicted by the mean field approxima tion is washed out by the Lipkin-Nogami approach. A much better agreem ent with the experimental data is reached with the new approach than w ith the Hartree-Fock-Bogoliubov one, especially at high spins.