Bulletin of the American Physical Society
2006 APS April Meeting
Saturday–Tuesday, April 22–25, 2006; Dallas, TX
Session E9: Minisymposium: Toward a Universal Density Functional Theory for Nuclei II |
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Sponsoring Units: DNP Chair: Scott Bogner, Ohio State University Room: Hyatt Regency Dallas Cumberland B |
Saturday, April 22, 2006 3:30PM - 4:06PM |
E9.00001: Density Functional Theory from Effective Field Theory Invited Speaker: The combination of progress in chiral effective field theory (EFT) for inter-nucleon interactions, the application of renormalization group (RG) techniques to nuclear systems, and advances in many-body computational tools and methods opens the possibility of \textit{constructive} density functional theory (DFT) for nuclei. Effective actions provide a natural framework for the development of EFT/DFT. One approach uses EFT power counting to define an order-by-order inversion of the generating functional in the presence of a source coupled to the density. This leads directly to Kohn-Sham DFT, which is widely used in condensed matter and quantum chemistry applications. Natural extensions lead to functionals of more general densities and the incorporation of pairing, consistent with phenomenological energy functionals for nuclei, which are themselves consistent with chiral EFT power counting. Chiral EFT offers a model-independent starting point, including a systematic approach to many-nucleon forces. The chiral inter-nucleon interactions are constructed with cutoffs in relative momentum much lower than those in conventional potentials, resulting in much softer interactions. If RG techniques are used to lower the cutoff further while preserving observables, Hartree-Fock plus second-order contributions (with three-body forces included) is found to be a good, possibly perturbative, first approximation for nuclear matter. The dominance of Hartree-Fock, in common with Coulomb DFT, raises hope for a quantitative microscopic construction. There are significant challenges to realizing this goal, both conceptual and technical, such as arise in extending DFT to self-bound systems. But the path is reasonably clear and meshes well with on-going efforts to develop, refine, and test phenomenological energy functionals for application across the mass table. [Preview Abstract] |
Saturday, April 22, 2006 4:06PM - 4:18PM |
E9.00002: Isoscalar Giant Dipole Resonance within Fermi Liquid Drop Model Oleksiy Pochivalov, Shalom Shlomo Recent highly accurate experimental data on Isoscalar Giant Dipole (ISGDR) and Monopole (ISGMR) Resonances in nuclei renewed interest in correct microscopic description of collective excitations. Hartree-Fock based Random-Phase-Approximation (HF-RPA) is a successful method of describing collective excitations in nuclei. However, recent fully self-consistent HF-RPA calculations, which reproduce the centroid energies of the ISGMR, systematically overestimate by 1.5-2.5 MeV results for the ISGDR energy comparing with experimentally obtained data. Also, the HF-RPA model does not provide description of the widths of giant resonances. We consider these issues within the semi-classical generalization of the mean field theory, namely, Fermi-Liquid-Drop-Model (FLDM). In this presentation, we provide description of the FLDM formalism in its application to ISGDR and ISGMR calculations. We present results of FLDM calculations for centroid energy and widths of the ISGDR and ISGMR in the four nuclei, namely, 90Zr, 116Sn, 144Sm, and 208Pb and compare with available experimental data. [Preview Abstract] |
Saturday, April 22, 2006 4:18PM - 4:30PM |
E9.00003: Fully self-consistent Hartree-Fock RPA calculations for nuclear giant resonances Tapas Sil, Shalom Shlomo The basic theory for the microscopic description of giant resonances is the Hartree-Fock(HF) based random phase approximation (RPA). A very accurate calculation within HF+RPA demands a sufficiently complete basis and in particular self-consistency, i.e., using exactly the same terms in the residual interaction that have been used in the underlying HF calculation. Apart from some fully self-consistent calculations most existing HF+RPA calculations are contaminated by self-consistency violation. We have carried out highly accurate fully self-consistent HF+RPA calculations for the strength functions of various modes of giant resonances for a host of nuclei. We check the accuracy of our calculations of the strength functions of giant resonances by comparing the RPA results with the corresponding ones of constrained HF for the case of isoscalar giant monopole (ISGMR) and the total energy weighted strengths with the corresponding energy weighted sum rule (EWSR). We have quantified very accurately the effects of self-consistency violation due to the omission of the spin-orbit (LS) and Coulomb (CO) particle-hole interaction on the centroid energy ($E_C$) which is commonly used to determine the nuclear matter incompressibility K. The effects of violations of self-consistency due to the ph LS or CO interactions are most significant for the ISGMR (3 to 5 times the experimental errors), leading to an uncertainty of around 20 MeV in K. [Preview Abstract] |
Saturday, April 22, 2006 4:30PM - 4:42PM |
E9.00004: New effective nucleon-nucleon interaction for mean-field approximation Au Vuong, Shalom Shlomo The effective Skyrme interaction has been used in mean-field models for several decades and many different parameterizations of the interaction have been realized to better reproduce nuclear masses, radii, and various other data. Today, there are more experimental data of nuclei far from stability line. It is time to improve the parameters of Skyrme-type effective nucleon-nucleon interactions. In this presentation, we present the procedure of the fitting of the mean-field results to an extensive set of experimental data with some constraints on the Skyrme parameters and some approximations in the mean-fields to obtain the parameters of the Skyrme type effective interactions, namely, KDE0 and KDE. We present results of fully self-consistent Hartree-Fock based Random-Phase-Approximation (HF+RPA) calculations for the centroid energies of the breathing modes in the four nuclei, namely, 90Zr, 116Sn, 144Sm, and 208Pb and compare with available experimental data. [Preview Abstract] |
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