Eur. Phys. J. A 14, 355-364 (2002)
DOI: 10.1140/epja/i2002-10029-5

The use of coherent states in the variational treatment of proton-neutron interactions

J.G. Hirsch¹, P.O. Hess¹ and O. Civitarese<sup>2

1</sup>  Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apdo. Postal 70-543, Mexico 04510 D.F.
²  Department of Physics, University of Plata, c.c. 67, (1900) La Plata, Argentina

hirsch@nuclecu.unam.mx
hess@nuclecu.unam.mx
civitare@venus.fisica.unlp.edu.ar

(Received: 19 February 2002 / Revised version: 15 April 2002 Communicated by P. Schuck)

Abstract
Coherent states are used as trial states to determine, variationally, the structure of the eigenvectors belonging to a schematic Hamiltonian consisting of single-particle, pairing and residual proton-neutron interaction terms. It is shown that the standard proton-neutron quasiparticle random-phase approximation ( pn-QRPA) is recovered, as a variational theory, by replacing quasiparticle pair creation and annihilation operators by bosons. It is also shown that an exact, algebra preserving, mapping of the Hamiltonian is needed to describe the spectrum beyond the QRPA phase transition. The role of the spurious components of the trial wave functions is discussed.

PACS
21.60.Jz - Hartree-Fock and random-phase approximations.
21.60.Fw - Models based on group theory.
23.40.Hc - Relation with nuclear matrix elements and nuclear structure.

© Società Italiana di Fisica, Springer-Verlag 2002