Chemische Untersuchung des Bernsteins

Nucleon pair structure of realistic many body wave functions

“…Consequently the vacua (2.3) were composed only out of like nucleon pairs coupled to even angular momentum and positive parity and thus only even spin positive parity states in doubly even nuclei could be investigated. Allowing for parity and proton-neutron mixing as well as admitting essentially complex transformations as proposed in [2] and applied rather successfully first in light [3] and later on also in heavier nuclei [10,11] was therefore a considerable progress: though time reversal and axial symmetry are still imposed, the vacua (2.3) are now constructed from like as well as unlike two nucleon pairs coupled to arbitary spin and parity quantum numbers and consequently states with arbitrary spin and parity in both doubly even and doubly odd nuclei have become accessible.…”

“…The development of approximate methods which are numerically feasible but still account for the essential degrees of freedom is therefore one of the central aims of microscopic nuclear structure theory. An example for such approximate methods are the various variational approaches of the VAMPIR family which have been developed within the last decade [1][2][3]. All these approaches use general symmetry-projected Hartree-Fock-Bogoliubov (HFB) determinants as basic building blocks of the theory and determine the underlying HBF transformations as well as the configuration mixing via chains of variational calculations of increasing sophistication.…”

A multi-configuration mixing approach with symmetry-projected complex Hartree-Fock-Bogoliubov determinants

“…If necessary, correlating symmetry projected configurations can be obtained by successive variational calculations. This is done in the FED VAMPIR approach [15]. Furthermore, using orthonormality contraints, the procedure can be easily extended to the description of excited states.…”

“…Furthermore, using orthonormality contraints, the procedure can be easily extended to the description of excited states. This is done in the EXCITED VAMPIR [13], and the even more general EXCITED FED VAMPIR [15] approaches. In principle, with the help of these approaches nuclear states of arbitrary complexity can be described.…”

“…Finally then, in this EXCITED VAMPIR model ( [13], [14]) the residual interaction between all the obtained solutions is diagonalized. A straightforward extension of these approaches are the Few Determinant (FED) VAMPIR and the EXCITED FED VAMPIR models ( [15], [16]), which approximate each state not by a single, but by a linear combination of several non-orthogonal symmetry-projected HFB configurations, which are again determined by independent, successive variations. By such chains of variational calculations the lowest few states of a given symmetry representation can be obtained, irrespective of their particular structure.…”