Nuclear shape transition at finite temperature in a relativistic mean field approach - art. no. 044307

The relativistic Hartree-BCS theory is applied to study the temperature dep endence of nuclear shape and pairing gap for Er-166 and Er-170. For both th e nuclei, we find that as temperature increases the pairing gap vanishes le ading to phase transition from superfluid to normal phase as is observed in nonrelativistic calculation. The deformation evolves from prolate shapes t o spherical shapes at T similar to 2.7 MeV. Comparison of our results for h eat capacity with the ones obtained in the nonrelativistic mean field frame work indicates that in the relativistic mean field theory the shape transit ion occurs at a temperature about 0.9 MeV higher and is relatively weaker. The effect of thermal shape fluctuations on the temperature dependence of d eformation is also studied. Relevant results for the level density paramete r are further presented.