834 research outputs found
Coexistence of spherical states with deformed and superdeformed bands in doubly magic 40-Ca; A shell model challenge
Large scale shell model calculations, with dimensions reaching 10**9, are
carried out to describe the recently observed deformed (ND) and superdeformed
(SD) bands based on the first and second excited 0+ states of 40-Ca at 3.35-MeV
and 5.21-MeV respectively. A valence space comprising two major oscillator
shells, sd and pf, can accommodate most of the relevant degrees of freedom of
this problem. The ND band is dominated by configurations with four particles
promoted to the pf-shell (4p-4h in short). The SD band by 8p-8h configurations.
The ground state of 40-Ca is strongly correlated, but the closed shell still
amounts to 65%. The energies of the bands are very well reproduced by the
calculations. The out-band transitions connecting the SD band with other states
are very small and depend on the details of the mixing among the different
np-nh configurations, in spite of that, the calculation describes them
reasonably. For the in-band transition probabilities along the SD band, we
predict a fairly constant transition quadrupole moment Q_0(t)~170 e fm**2 up to
J=10, that decreases toward the higher spins. We submit also that the J=8
states of the deformed and superdeformed band are maximally mixed.Comment: 12 pages, 9 figure
Backbending in 50Cr
The collective yrast band and the high spin states of the nucleus 50Cr are
studied using the spherical shell model and the HFB method. The two
descriptions lead to nearly the same values for the relevant observables. A
first backbending is predicted at I=10\hbar corresponding to a collective to
non-collective transition. At I=16\hbar a second backbending occurs, associated
to a configuration change that can also be interpreted as an spherical to
triaxial transition.Comment: ReVTeX v 3.0 epsf.sty, 5 pages, 5 figures included. Full Postscript
version available at http://www.ft.uam.es/~gabriel/Cr50art.ps.g
Canonical form of Hamiltonian matrices
On the basis of shell model simulations, it is conjectured that the Lanczos
construction at fixed quantum numbers defines---within fluctuations and
behaviour very near the origin---smooth canonical matrices whose forms depend
on the rank of the Hamiltonian, dimensionality of the vector space, and second
and third moments. A framework emerges that amounts to a general Anderson model
capable of dealing with ground state properties and strength functions. The
smooth forms imply binomial level densities. A simplified approach to canonical
thermodynamics is proposed.Comment: 4 pages 6 figure
Shell Model Study of the Double Beta Decays of Ge, Se and Xe
The lifetimes for the double beta decays of Ge, Se and
Xe are calculated using very large shell model spaces. The two neutrino
matrix elements obtained are in good agreement with the present experimental
data. For eV we predict the following upper bounds to the
half-lives for the neutrinoless mode: , and . These results are the first from a new generation of Shell
Model calculations reaching O(10) dimensions
Energy efficiency parametric design tool in the framework of holistic ship design optimization
Recent International Maritime Organization (IMO) decisions with respect to measures to reduce the emissions from maritime greenhouse gases (GHGs) suggest that the collaboration of all major stakeholders of shipbuilding and ship operations is required to address this complex techno-economical and highly political problem efficiently. This calls eventually for the development of proper design, operational knowledge, and assessment tools for the energy-efficient design and operation of ships, as suggested by the Second IMO GHG Study (2009). This type of coordination of the efforts of many maritime stakeholders, with often conflicting professional interests but ultimately commonly aiming at optimal ship design and operation solutions, has been addressed within a methodology developed in the EU-funded Logistics-Based (LOGBASED) Design Project (2004â2007). Based on the knowledge base developed within this project, a new parametric design software tool (PDT) has been developed by the National Technical University of Athens, Ship Design Laboratory (NTUA-SDL), for implementing an energy efficiency design and management procedure. The PDT is an integral part of an earlier developed holistic ship design optimization approach by NTUA-SDL that addresses the multi-objective ship design optimization problem. It provides Pareto-optimum solutions and a complete mapping of the design space in a comprehensive way for the final assessment and decision by all the involved stakeholders. The application of the tool to the design of a large oil tanker and alternatively to container ships is elaborated in the presented paper
Full shell model calculation of the binding energies of the nuclei
Binding energies and other global properties of nuclei in the middle of the
shell, such as M1, E2 and Gamow-Teller sum rules, have been obtained using
a new Shell Model code (NATHAN) written in quasi-spin formalism and using a
-coupled basis. An extensive comparison is made with the recently
available Shell Model Monte Carlo results using the effective interaction KB3.
The binding energies for -nearly- all the nuclei are compared with
the measured (and extrapolated) results.Comment: 7 page
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