Microscopic Cluster Model for Exotic Nuclei

For a better understanding of the dynamics of exotic nuclei it is of crucial importance to develop a practical microscopic theory easy to be applied to a wide range of masses. Theoretically the basic task consists in formulating an easy solvable theory able to reproduce structures and transitions of known nuclei which should be then used to calculate the sparely known properties of proton- or neutron-rich nuclei. In this paper we start by calculating energies and distributions of A\leq4 nuclei withing a unitary correlation model restricted to include only two-body correlations. The structure of complex nuclei is then calculated extending the model to include correlation effects of higher order.Comment: 10 pages, 4 figures. Final Version to be published in "Progress of Particle and Nuclear Physics (2007

Correlated EoM and Distributions for A=6 Nuclei

Energy spectra and electromagnetic transitions of nuclei are strongly depending from the correlations of the bound nucleons. Two particle correlations are responsible for the scattering of model particles either to low momentum- or to high momentum-states. The low momentum states form the model space while the high momentum states are used to calculate the G-matrix. The three and higher order particle correlations do not play a role in the latter calculation especially if the correlations induced by the scattering operator are of sufficient short range. They modify however, via the long tail of the nuclear potential, the Slater determinant of the A particles by generating excited Slater's determinants. In this work the influence of the correlations on the level structure and ground state distributions of even open shell nuclei is analyzed via the boson dynamic correlation model BDCM. The model is based on the unitary operator $e^S$ ({\it S} is the correlation operator) formalism which in this paper is presented within a non perturbative approximation. The low lying spectrum calculated for $^6$Li reproduce very well the experimental spectrum while for $^6$He a charge radius slightly larger than that obtained within the isotopic-shift (IS) theory has been calculated. Good agreement between theoretical and experimental results has been obtained without the introduction of a genuine three body force.Comment: 25 pages 4 figures. To be published in the Progress Theoretical Physic

Cluster Transformation Coefficients for Structure and Dynamics Calculations in n-Particle Systems: Atoms, Nuclei, and Quarks

The structure and dynamics of an n-particle system are described with coupled nonlinear Heisenberg's commutator equations where the nonlinear terms are generated by the two-body interaction that excites the reference vacuum via particle-particle and particle-hole excitations. Nonperturbative solutions of the system are obtained with the use of dynamic linearization approximation and cluster transformation coefficients. The dynamic linearization approximation converts the commutator chain into an eigenvalue problem. The cluster coefficients factorize the matrix elements of the (n)-particles or particle-hole systems in terms of the matrix elements of the (n-1)-systems coupled to a particle-particle, particle-hole, and hole-hole boson. Group properties of the particle-particle, particle-hole, and hole-hole permutation groups simplify the calculation of these coefficients. The particle-particle vacuum-excitations generate superconductive diagrams in the dynamics of 3-quarks systems. Applications of the model to fermionic and bosonic systems are discussed.Comment: 13 pages, 5 figures, Wigner Proceedings for Conference Wigner Centenial Pecs, July 8-12, 200

Extended Cluster Model for Light, and Medium Nuclei

The structures, the electromagnetic transitions, and the beta decay strengths of exotic nuclei are investigated within an extended cluster model. We start by deriving an effective nuclear Hamiltonian within the $S_2$ correlation operator. Tensor forces are introduced in a perturbative expansion which includes up to the second order terms. Within this Hamiltonian we calculate the distributions and the radii of A=3,~4 nuclei. For exotic nuclei characterized by n valence protons/neutrons we excite the structure of the closed shell nuclei via mixed modes formed by considering correlations operators of higher order. Good results have been obtained for the calculated transitions and for the beta decay transition probabilities.Comment: 8-pages, 5-figure

Investigation on the Use of a Multiphase Eulerian CFD solver to simulate breaking waves

The main challenge in CFD multiphase simulations of breaking waves is the wide range of interfacial length scales occurring in the flow: from the free surface measurable in meters down to the entrapped air bubbles with size of a fraction of a millimeter. This paper presents a preliminary investigation on a CFD model capable of handling this problem. The model is based on a solver, available in the open-source CFD toolkit OpenFOAM, which combines the Eulerian multi-fluid approach for dispersed flows with a numerical interface sharpening method. The solver, enhanced with additional formulations for mass and momentum transfer among phases, was satisfactorily tested against an experimental bubble column flow. The model was then used to simulate the propagation of a laboratory solitary breaking wave. The motion of the free surface was successfully reproduced up to the breaking point. Further implementations are needed to simulate the air entrainment phenomeno

Unusual polymerization in the Li4C60 fulleride

Li4C60, one of the best representatives of lithium intercalated fullerides, features a novel type of 2D polymerization. Extensive investigations, including laboratory x-ray and synchrotron radiation diffraction, 13C NMR, MAS and Raman spectroscopy, show a monoclinic I2/m structure, characterized by chains of [2+2]-cycloaddicted fullerenes, sideways connected by single C-C bonds. This leads to the formation of polymeric layers, whose insulating nature, deduced from the NMR and Raman spectra, denotes the complete localization of the electrons involved in the covalent bonds.Comment: 7 pages, 6 figures, RevTex4, submitted to Phys. Rev.

Surface-sensitive NMR in optically pumped semiconductors

We present a scheme of surface-sensitive nuclear magnetic resonance in optically pumped semiconductors, where an NMR signal from a part of the surface of a bulk compound semiconductor is detected apart from the bulk signal. It utilizes optically oriented nuclei with a long spin-lattice relaxation time as a polarization reservoir for the second (target) nuclei to be detected. It provides a basis for the nuclear spin polarizer [IEEE Trans. Appl. Supercond. 14, 1635 (2004)], which is a polarization reservoir at a surface of the optically pumped semiconductor that polarizes nuclear spins in a target material in contact through the nanostructured interfaces.Comment: 4 pages, 5 figure

Caracterização da madeira de Taxi-branco-da-terra-firme (Sclerolobium paniculatum Vogel) para energia.

Este trabalho analisa a qualidade da madeira, para fins energéticos, de árvores de Sclerolobium paniculatum Vogel, de ocorrência natural e de plantio experimental (cinco árvores cada). Não foram constatadas diferenças significativas entre as duas origens. A madeira possui características comparáveis às tradicionalmente utilizadas para energia no Sul do Brasil