Constant temperature model for nuclear level density

We study physics related to the nuclear level density calculated either in a realistic shell model or, equivalently, with the use of the statistical moments method. At excitation energy up to 12-15 MeV, the obtained level density grows exponentially being well described by the so-called constant temperature model. We discuss the physical meaning of the effective temperature parameter and its dependence on the interaction Hamiltonian including nucleon pairing and deformation effects. The possible interpretation relates the underlying physics with the gradual chaotization of typical wave functions rather than with the pairing phase transition.