BRST Treatment of the Bohr Collective Hamiltonian at High Spins

The BRST treatment of triaxial systems rotating at high spins is used to solve perturbatively the $\gamma$-independent Bohr collective hamiltonian.Comment: 10 pages in LaTeX using Esp-LaTeX and Feynman package

Perturbative description of nuclear double beta decay transitions

A consistent treatment of intrinsic and collective coordinates is applied to the calculation of matrix elements describing nuclear double beta decay transitions. The method, which was developed for the case of nuclear rotations, is adapted to include isospin and number of particles degrees of freedom. It is shown that the uncertainties found in most models, in dealing with these decay modes, are largely due to the mixing of physical and spurious effects in the treatment of isospin dependent interactions.Comment: 4 pages, 2 figures, RevTe

Anomalous rotational-alignment in N=Z nuclei and residual neutron-proton interaction

Recent experiments have demonstrated that the rotational-alignment for the $N=Z$ nuclei in the mass-80 region is considerably delayed as compared to the neighboring $N \ne Z$ nuclei. We investigate whether this observation can be understood by a known component of nuclear residual interactions. It is shown that the quadrupole-pairing interaction, which explains many of the delays known in rare-earth nuclei, does not produce the substantial delay observed for these $N=Z$ nuclei. However, the residual neutron-proton interaction which is conjectured to be relevant for $N=Z$ nuclei is shown to be quite important in explaining the new experimental data.Comment: 4 pages, 3 figures, final version accepted by Phys. Rev. C as a Rapid Communicatio

Anomalous Crossing Frequency in Odd Proton Nuclei

A generic explanation for the recently observed anomalous crossing frequencies in odd proton rare earth nuclei is given. As an example, the proton ${1\over 2} [541]$ band in $^{175}$Ta is discussed in detail by using the angular momentum projection theory. It is shown that the quadrupole pairing interaction is decisive in delaying the crossing point and the changes in crossing frequency along the isotope chain are due to the different neutron shell fillings

Description of superdeformed nuclei in the interacting boson model

The interacting boson model is extended to describe the spectroscopy of superdeformed bands. Microscopic structure of the model in the second minimum is discussed and superdeformed bosons are introduced as the new building blocks. Solutions of a quadrupole Hamiltonian are implemented through the $1/N$ expansion method. Effects of the quadrupole parameters on dynamic moment of inertia and electric quadrupole transition rates are discussed and the results are used in a description of superdeformed bands in the Hg-Pb and Gd-Dy regions.Comment: 18 pages revtex, 9 figures available upon reques

Lagrangian Becchi-Rouet-Stora-Tyutin treatment of collective coordinates

The Becchi-Rouet-Stora-Tyutin (BRST) treatment for the quantization of collective coordinates is considered in the Lagrangian formalism. The motion of a particle in a Riemannian manifold is studied in the case when the classical solutions break a non-abelian global invariance of the action. Collective coordinates are introduced, and the resulting gauge theory is quantized in the BRST antifield formalism. The partition function is computed perturbatively to two-loops, and it is shown that the results are independent of gauge-fixing parameters.Comment: LaTeX file, 26 pages, PostScript figures at end of fil

Schematic and realistic model calculations of the isovector spin monopole excitations in 116In

The excitation of Gamow-Teller (GT) and isovector spin monopole (IVSM) J π = 1+ modes in 116In by (p,n) and (n, p) charge-exchange reactions on 116Cd and on 116Sn, respectively, is studied within the framework of the quasiparticle random-phase approximation. The calculations have been performed both for schematic and realistic model situations. It appears that the calculated admixture of the IVSM and Gamow-Teller (GT) J π = 1+ excitations is negligible and that the contribution to the strength above 20 MeV of excitation energy, in 116In, is due to the IVSM (σr2t±) mode. This result is compared with the recent experimental work that reported a large amount of both (p,n) and (n,p) strength beyond 10 MeV of excitation energy in 116In. This measured excess strength has led to speculations about its importance for the double beta decay rate of 116Cd.peerReviewe