It is shown that the anomalously large double binding energy differences for even-even N = Z nuclei are a consequence of Wigner's SU(4) symmetry. These, and similar quantities for odd-mass and odd-odd nuclei, provide a simple and distinct signature of this symmetry in N≃Z nuclei

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The phase diagram of models with configuration mixing is investigated in mean-field approximation. The configurations correspond to different limits of a dynamical algebra U(n), such as U(n-1) and SO(n), and are allowed to mix. It is shown that this diagram has unusual properties not present in models with a single configuration. Applications to nuclear and molecular physics are discussed

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Abstract. We show that the ground state of a Bose-Einstein condensate of atoms with hyperfine spin f = 2 can be either spin aligned, condensed into pairs of atoms coupled to F = 0, or condensed into triplets of atoms coupled to F = 0. The complete phase diagram is constructed for f = 2 and the generic properties of the phase diagram are obtained for f > 2.

Starting from a simplified model, treating proton two-particle two-hole excitations in interaction with low-lying quadrupole vibrational configurations, we calculate the low-lying levels in even-even "" Cd. %e also present configuration mixing calculations within the framework of the interacting boson model. Both approaches give a good description of the quintuplet of levels occurring below E =1.5 MeV in "'" Cd (energy spectra and a detailed account of E2 and EO decay properties). Finally, we point out some similarities between both approaches and. try to interpret the interacting boson model mixing parameters in terms of shell-model quantities (two-body matrix elements and single-particle energies). NUCLEAR STRUCTURE Collective excitations in "2*" Cd; shellmodel intruder states; interacting boson model configuration mixing.

As an alternative to Wigner's spin-isospin SU(4) symmetry, known to be broken in heavier nuclei, a pseudo-SU(4) symmetry is proposed which follows from the combined invariance in pseudospin and isospin. The pseudo-SU(4) scheme is tested in N, Z . 28 nuclei, and its consequences with regard to Gamow-Teller b decay are pointed out. [S0031-9007(99)08617-2]