989 research outputs found
Canonical and microcanonical ensemble descriptions of thermal pairing within BCS and quasiparticle RPA
We propose a description of pairing properties in finite systems within the
canonical and microcanonical ensembles. The approach is derived by solving the
BCS and self-consistent quasiparticle random-phase approximation with the
Lipkin-Nogami particle-number projection at zero temperature. The obtained
eigenvalues are embedded into the canonical and microcanonical ensembles. The
results obtained are found in quite good agreement with the exact solutions of
the doubly-folded equidistant multilevel pairing model as well as the
experimental data for Fe nucleus. The merit of the present approach
resides in its simplicity and its application to a wider range of particle
number, where the exact solution is impracticable.Comment: 10 pages, 2 figures, accepted for publication in Phys. Rev.
Nuclear pairing at finite temperature and angular momentum
An approach is proposed to nuclear pairing at finite temperature and angular
momentum, which includes the effects of the quasiparticle-number fluctuation
and dynamic coupling to pair vibrations within the self-consistent
quasiparticle random-phase approximation. The numerical calculations of pairing
gaps, total energies, and heat capacities are carried out within a doubly
folded multilevel model as well as several realistic nuclei. The results
obtained show that, in the region of moderate and strong couplings, the sharp
transition between the superconducting and normal phases is smoothed out,
causing a thermal pairing gap, which does not collapse at a critical
temperature predicted by the conventional Bardeen-Cooper-Schrieffer's (BCS)
theory, but has a tail extended to high temperatures. The theory also predicts
the appearance of a thermally assisted pairing in hot rotating nuclei.Comment: 4 pages, 1 figure, To appear in the Proceedings of the First Workshop
on State of the Art in Nuclear Cluster Physics, Strasbourg 13 - 16 May, 200
- …