Pairing interactions and vanishing pairing correlations in hot nuclei

Finite temperature Hartree–Fock–Bogoliubov calculations are performed in Sn isotopes using Skyrme and zero-range, density-dependent pairing interactions. For both stable and very neutron-rich nuclei the critical temperature at which pairing correlations vanish is independent of the volume/surface nature of the pairing interaction. The value of the critical temperature follows approximatively the empirical rule Tc≃0.5ΔT=0 for all the calculated isotopes, showing that the critical temperature could be deduced from the pairing gap at zero temperature. On the other hand, the pairing gap at temperatures just below Tc is strongly sensitive to the volume/surface nature of the pairing interaction.