On a collective pair approximation for low-energy nuclear spectra

Werner Brandt, Stig Lundqvist

Fang Ni, Nobuo Hinohara, Takashi Nakatsukasa

For a description of large-amplitude collective motion associated with nuclear pairing, requantization of time-dependent mean-field dynamics is performed using the stationary-phase approximation (SPA) to the path integral. We overcome the difficulty of the SPA, which is known to be applicable to integrable systems only, by developing a requantization approach combining the SPA with the adiabatic self-consistent collective coordinate method (ASCC+SPA). We apply the ASCC+SPA to multilevel pairing models, which are nonintegrable systems, to study the nuclear pairing dynamics. The ASCC+SPA gives a reasonable description of low-lying excited ${0}^{+}$ states in nonintegrable pairing systems.

James P. Vary, Angelo Plastino

We develop a method for treating the $N$-fermion problem as a system of correlated pairs of particles. Coherent pair states are introduced and a variational as well as a secular method are discussed for providing upper bounds to the exact ground state and approximations to the low lying spectra. Specific applications to two soluble models are presented. For these models the coherent correlated pair method is superior to the Bardeen-Cooper-Schrieffer approximation and to the Hartree-Fock approximation and in fact yields the exact solutions for all particle numbers and sufficiently large coupling constants.NUCLEAR STRUCTURE Correlated pairs; coherent states; upper bound to ground state energy; applications to soluble $N$-fermion models.

T. Papenbrock, David J. Dean, J. R. Gour +4 more

H.C. Pradhan, Yukihisa Nogami, J. Law

HERVÉ MOLIQUE, J. Dudek

In this article we present a method to parametrise the exact solutions to the nuclear pairing problem, for realistic large-scale many-body spaces. This new approach allows for rapid and quite accurate estimates of the pairing influence on the excitation energies of the nucleus, treated in the standard mean-field approximation.