Pairing in hot rotating nuclei

Abstract

Nuclear pairing properties are studied within an approach that includes the quasiparticle-number fluctuation (QNF) and coupling to the quasiparticle-pair vibrations at finite temperature and angular momentum. The formalism is developed to describe non-collective rotations about the symmetry axis. The numerical calculations are performed within a doubly-folded equidistant multilevel model as well as several realistic nuclei. The results obtained for the pairing gap, total energy and heat capacity show that the QNF smoothes out the sharp SN phase transition and leads to the appearance of a thermally assisted pairing gap in rotating nuclei at finite temperature. The corrections due to the dynamic coupling to SCQRPA vibrations and particle-number projection are analyzed. The effect of backbending of the momentum of inertia as a function of squared angular velocity is also discussed.Comment: 30 pages and 9 figures. Accepted in Phys. Rev.

Damping of giant dipole resonances in hot rotating nuclei

“…The latter is aligned with the direction of the total angular momentum within the quantum mechanical uncertainty [11][12][13]. As the result, the total angular momentum is completely determined by its z-projection M alone.…”

Specific shear viscosity in hot rotating systems of paired fermions

“…The schematic model consists of Ω doubly folded equidistant levels, which interact via a pairing force with parameter G. Before switching on the pairing interaction, Ω/2 lowest levels are occupied by N = Ω particles with 2 particles on each levels with spin projections ±m k = ±1/2, ±3/2, ..., ±Ω − 1/2, whereas Ω/2 upper levels are empty. The distance between levels is chosen equal to 1 MeV [8]. As for the realistic nuclei, 20 O, 44 Ca, and 120 Sn are considered.…”

“…Since the FTBCS1+SCQRPA has already been discussed thoroughly in Refs. [7][8][9], we summarize below only their main results, which are necessary for calculations in the present paper.…”

“…[7,8]. The FTBCS1+SCQRPA includes the effect caused by the quasiparticle-number fluctuation (QNF) at finite temperature (FT), which is neglected in the standard BCS solution of the pairing problem, as well as the effect due to coupling to pairing vibration within the selfconsistent quasiparticle random-phase approximation (SCQRPA).…”

“…(15) - (17), ν µ = Q + µ Q µ is the phonon occupation number, which is found by solving a set of coupled equations (31) -(35) in Ref. [8], and ε is a sufficient small parameter.…”