Ground state of medium-heavy doubly-closed shell nuclei in correlated basis function theory

The correlated basis function theory is applied to the study of medium-heavy doubly closed shell nuclei with different wave functions for protons and neutrons and in the jj coupling scheme. State dependent correlations including tensor correlations are used. Realistic two-body interactions of Argonne and Urbana type, together with three-body interactions have been used to calculate ground state energies and density distributions of the 12C, 16O, 40Ca, 48Ca and 208Pb nuclei.Comment: Latex 10 pages, 3 Tables, 10 Figure

Baroclinic instability with variable gravity: A perturbation analysis

Solutions for a quasigeostrophic baroclinic stability problem in which gravity is a function of height were obtained. Curvature and horizontal shear of the basic state flow were omitted and the vertical and horizontal temperature gradients of the basic state were taken as constant. The effect of a variable dielectric body force, analogous to gravity, on baroclinic instability for the design of a spherical, baroclinic model for Spacelab was determined. Such modeling could not be performed in a laboratory on the Earth's surface because the body force could not be made strong enough to dominate terrestrial gravity. A consequence of the body force variation and the preceding assumptions was that the potential vorticity gradient of the basic state vanished. The problem was solved using a perturbation method. The solution gives results which are qualitatively similar to Eady's results for constant gravity; a short wavelength cutoff and a wavelength of maximum growth rate were observed. The averaged values of the basic state indicate that both the wavelength range of the instability and the growth rate at maximum instability are increased. Results indicate that the presence of the variable body force will not significantly alter the dynamics of the Spacelab experiment. The solutions are also relevant to other geophysical fluid flows where gravity is constant but the static stability or Brunt-Vaisala frequency is a function of height

Renormalized Fermi hypernetted chain approach in medium-heavy nuclei

The application of the Correlated basis function theory and of the Fermi hypernetted chain technique, to the description of the ground state of medium-heavy nuclei is reviewed. We discuss how the formalism, originally developed for symmetric nuclear matter, should be changed in order to describe finite nuclear systems, with different number of protons and neutrons. This approach allows us to describe doubly closed shell nuclei by using microscopic nucleon-nucleon interactions. We presents results of numerical calculations done with two-nucleon interactions of Argonne type,implemented with three-body forces of Urbana type. Our results regard ground-state energies, matter, charge and momentum distributions, natural orbits, occupation numbers, quasi-hole wave functions and spectroscopic factors of 12C, 16O, 40Ca, 48Ca and 208Pb nuclei.Comment: 127 Pages, 37 figures, Accepted for publication in Physics Report

Critical point symmetries in boson-fermion systems. The case of shape transition in odd nuclei in a multi-orbit model

We investigate phase transitions in boson-fermion systems. We propose an analytically solvable model (E(5/12)) to describe odd nuclei at the critical point in the transition from the spherical to $\gamma$-unstable behaviour. In the model, a boson core described within the Bohr Hamiltonian interacts with an unpaired particle assumed to be moving in the three single particle orbitals j=1/2,3/2,5/2. Energy spectra and electromagnetic transitions at the critical point compare well with the results obtained within the Interacting Boson Fermion Model, with a boson-fermion Hamiltonian that describes the same physical situation.Comment: Phys. Rev. Lett. (in press

Momentum distributions and spectroscopic factors of doubly-closed shell nuclei in correlated basis function theory

The momentum distributions, natural orbits, spectroscopic factors and quasi-hole wave functions of the C12, O16, Ca40, Ca48, and Pb208 doubly closed shell nuclei, have been calculated in the framework of the Correlated Basis Function theory, by using the Fermi hypernetted chain resummation techniques. The calculations have been done by using the realistic Argonne v8' nucleon-nucleon potential, together with the Urbana IX three-body interaction. Operator dependent correlations, which consider channels up to the tensor ones, have been used. We found noticeable effects produced by the correlations. For high momentum values, the momentum distributions show large enhancements with respect to the independent particle model results. Natural orbits occupation numbers are depleted by about the 10\% with respect to the independent particle model values. The effects of the correlations on the spectroscopic factors are larger on the more deeply bound states.Comment: Modified version of the previous paper (there are new figures). The paper has been accepted for publication in Physical Review

Intrinsic structure of two-phonon states in the interacting boson model

A general study of excitations up to two-phonon states is carried out using the intrinsic-state formalism of the Interacting Boson Model (IBM). Spectra and transitions for the different dynamical symmetries are analyzed and the correspondence with states in the laboratory frame is established. The influence of multi-phonon states is discussed. The approach is useful in problems where the complexity of the IBM spectrum renders the analysis in the laboratory frame difficult.Comment: 22 pages, TeX (ReVTeX). 7 eps figures. Submitted to Nucl. Phys.

Evidence of strong dynamic core excitation in 19^{19}C resonant break-up

The resonant break-up of $^{19}$C on protons measured at RIKEN [Phys. Lett. B 660, 320 (2008)] is analyzed in terms of a valence-core model for $^{19}$C including possible core excitations. The analysis of the angular distribution of a prominent peak appearing in the relative-energy spectrum could be well described with this model and is consistent with the previous assignment of $5/2^{+}$ for this state. Inclusion of core-excitation effects are found to be essential to give the correct magnitude of the cross section for this state. By contrast, the calculation assuming an inert $^{18}$C core is found to largely underestimate the data.Comment: 5 pages, 2 figures, to be submitte