Collective enhancement of nuclear level density in the interacting boson model

The interacting boson model (IBM) is applied at finite temperature for evaluation of a collective enhancement factor in nuclear level densities in the form of a canonical partition function. The most crucial variable turns out to be the effective boson number, whose temperature dependence is studied in the frame of a Nilsson-Bardeen-Cooper-Schrieffer model. Numerical results are obtained in the three IBM limiting symmetries.