A theoretical analysis of mid-mass neutron halos. What changes going from few- to many-body systems regarding neutron halos?

The present contribution summarizes the content and slightly updates the discussion of a recently proposed theoretical analysis of the halo phenomenon in many-fermion systems. We focus here on applications to potential neutron halos in mid-mass nuclei.Comment: 17 pages, 19 figures. arXiv admin note: substantial text overlap with arXiv:nucl-th/070205

Pairing in finite nuclei from low-momentum two- and three-nucleon interactions

The present contribution reviews recent advances made toward a microscopic understanding of superfluidity in nuclei using many-body methods based on the BCS ansatz and low-momentum inter-nucleon interactions, themselves based on chiral effective field theory and renormalization group techniques.Comment: 15 pages, contribution to "50 years of nuclear BCS", edited by R.A. Broglia and V. Zelevinsk

Non-empirical pairing functional

The present contribution reports the first systematic finite-nucleus calculations performed using the Energy Density Functional method and a non-empirical pairing functional derived from low-momentum interactions. As a first step, the effects of Coulomb and the three-body force are omitted while only the bare two-nucleon interaction at lowest order is considered. To cope with the finite-range and non-locality of the bare nuclear interaction, the 1S0 channel of Vlowk is mapped onto a convenient operator form. For the first time, neutron-neutron and proton-proton pairing correlations generated in finite nuclei by the direct term of the two-nucleon interaction are characterized in a systematic manner. Eventually, such predictions are compared to those obtained from empirical local functionals derived from density-dependent zero range interactions. The characteristics of the latter are analyzed in view of that comparison and a specific modification of their isovector density dependence is suggested to accommodate Coulomb effects and the isovector trend of neutron gaps at the same time.Comment: To be printed in the Proceedings of the International Les Houches School on "Exotic Nuclei: New Challenges", May 7-18 2007, Les Houches, France, 9 pages, 2 figures. Minor modification

HFB calculations with a microscopic pairing interaction

Hartree-Fock-Bogolyubov (HFB) calculations making use of a recently proposed microscopic effective pairing interaction are presented. The interaction was shown to reproduce the pairing properties provided by the realistic $AV18$ force very accurately in infinite matter. Although finite-ranged and non-local, it makes 3D HFB calculations in coordinate space tractable. As a first application, basic pairing properties of calcium isotopes in their ground-state are studied. By comparing the results with those obtained using a standard Density-Dependent Delta Interaction, the crucial isovector character of the microscopic interaction is highlighted.Comment: 6 pages, 6 figures. Proceedings of the Conference on Nuclei at the Limits, ANL, 2004. They will be published in the AIP Conference Proceedings Serie

Configuration mixing within the energy density functional formalism: pathologies and cures

Configuration mixing calculations performed in terms of the Skyrme/Gogny Energy Density Functional (EDF) rely on extending the Single-Reference energy functional into non-diagonal EDF kernels. The standard way to do so, based on an analogy with the pure Hamiltonian case and the use of the generalized Wick theorem, is responsible for the recently observed divergences and steps in Multi-Reference calculations. We summarize here the minimal solution to this problem recently proposed [Lacroix et al, arXiv:0809.2041] and applied with success to particle number restoration[Bender et al, arXiv:0809.2045]. Such a regularization method provides suitable corrections of pathologies for EDF depending on integer powers of the density. The specific case of fractional powers of the density[Duguet et al, arXiv:0809.2049] is also discussed.Comment: 5 pages, Proceedings of the French-Japanese Symposium, September 2008. To be published in Int. J. of Mod. Phys.

Ab-initio Gorkov-Green's function calculations of open-shell nuclei

We present results from a new ab-initio method that uses the self-consistent Gorkov Green's function theory to address truly open-shell systems. The formalism has been recently worked out up to second order and is implemented here in nuclei for the first time on the basis of realistic nuclear forces. We find good convergence of the results with respect to the basis size in Ca44 and Ni74 and discuss quantities of experimental interest including ground-state energies, pairing gaps and particle addition/removal spectroscopy. These results demonstrate that the Gorkov method is a valid alternative to multireference approaches for tackling degenerate or near degenerate quantum systems. In particular, it increases the number of mid-mass nuclei accessible in an ab-initio fashion from a few tens to a few hundreds.Comment: 5 pages, 3 figure

Pairing schemes for HFB calculations of nuclei

Several pairing schemes currently used to describe superfluid nuclei through Hartree-Fock-Bogolyubov (HFB) calculations are briefly reviewed. We put a particular emphasis on the regularization recipes used in connection with zero-range forces and on the density dependence which usually complement their definition. Regarding the chosen regularization process, the goal is not only to identify the impact it may or may not have on pairing properties of nuclei through spherical 1D HFB calculations but also to assess its tractability for systematic axial 2D and 3D mean-field and beyond-mean-field calculations.Comment: 7 pages, 7 figures, Invited talk at the Workshop on New developments in Nuclear Self-Consistent Mean-Field Theories, Yukawa Institute for Theoretical Physics, Kyoto, Japan, May 30 - June 1, 2005, Yukawa Institute for Theoretical Physics Report Series (Soryushi-ron kenkyu