277 research outputs found
Microscopic Determinations of Fission Barriers, (MEAN-Field and Beyond)
With a help of the selfconsistent Hartree-Fock-Bogoliubov (HFB) approach with
the D1S effective Gogny interaction and the Generator Coordinate Method (GCM)
we incorporate the transverse collective vibrations to the one-dimensional
model of the fission-barrier penetrability based on the traditional WKB method.
The average fission barrier corresponding to the least-energy path in the
two-dimensional potential energy landscape as function of quadrupole and
octupole degrees of freedom is modified by the influence of the transverse
collective vibrations along the nuclear path to fission. The set of transverse
vibrational states built in the fission valley corresponding to a successively
increasing nuclear elongation produces the new energy barrier which is compared
with the least-energy barrier. These collective states are given as the
eigensolutions of the GCM purely vibrational Hamiltonian. In addition, the
influence of the collective inertia on the fission properties is displayed, and
it turns out to be the decisive condition for the possible transitions between
different fission valleys.Comment: 12 pages, 5 figures, presented at XIII Workshop of Nuclear Physics,
Kazimierz Dolny, 2006 (Poland
Structure properties of even-even actinides
Structure properties of fifty five even-even actinides have been calculated
using the Gogny D1S force and the Hartree-Fock-Bogoliubov approach as well as
the configuration mixing method. Theoretical results are compared with
experimental data.Comment: 5 pages, 5 figures, proceeding of FUSION0
Towards a microscopic description of the fission process
One major issue in nuclear physics is to develop a consistent model able to describe on the same footing the different aspects of the fission process, i.e. properties of the fissioning system, fission dynamics and fragment distributions. Microscopic fission studies based on the mean-field approximation are here presented
Structure properties of Th and Fm fission fragments: mean field analysis with the Gogny force
The constrained Hartree-Fock-Bogoliubov method is used with the Gogny
interaction D1S to calculate potential energy surfaces of fissioning nuclei
Th and Fm up to very large deformations. The
constraints employed are the mass quadrupole and octupole moments. In this
subspace of collective coordinates, many scission configurations are identified
ranging from symmetric to highly asymmetric fragmentations. Corresponding
fragment properties at scission are derived yielding fragment deformations,
deformation energies, energy partitioning, neutron binding energies at
scission, neutron multiplicities, charge polarization and total fragment
kinetic energies.Comment: 15 pages, 23 figures, accepted for publication in Phys. Rev. C (2007
Structure of even-even nuclei using a mapped collective Hamiltonian and the D1S Gogny interaction
A systematic study of low energy nuclear structure at normal deformation is
carried out using the Hartree-Fock-Bogoliubov theory extended by the Generator
Coordinate Method and mapped onto a 5-dimensional collective quadrupole
Hamiltonian. Results obtained with the Gogny D1S interaction are presented from
dripline to dripline for even-even nuclei with proton numbers Z=10 to Z=110 and
neutron numbers N less than 200. The properties calculated for the ground
states are their charge radii, 2-particle separation energies, correlation
energies, and the intrinsic quadrupole shape parameters. For the excited
spectroscopy, the observables calculated are the excitation energies and
quadrupole as well as monopole transition matrix elements. We examine in this
work the yrast levels up to J=6, the lowest excited 0^+ states, and the two
next yrare 2^+ states. The theory is applicable to more than 90% of the nuclei
which have tabulated measurements. The data set of the calculated properties of
1712 even-even nuclei, including spectroscopic properties for 1693 of them, are
provided in CEA website and EPAPS repository with this article \cite{epaps}.Comment: 51 pages with 26 Figures and 4 internal tables; this version is
accepted by Physical Review
Microscopic and non-adiabatic Schr\"odinger equation derived from the Generator Coordinate Method based on 0 and 2 quasiparticle HFB states
A new approach called the Schr\"odinger Collective Intrinsic Model (SCIM) has
been developed to achieve a microscopic description of the coupling between
collective and intrinsic excitations. The derivation of the SCIM proceeds in
two steps. The first step is based on a generalization of the symmetric moment
expansion of the equations derived in the framework of the Generator Coordinate
Method (GCM), when both Hartree-Fock-Bogoliubov (HFB) states and
two-quasi-particle excitations are taken into account as basis states. The
second step consists in reducing the generalized Hill and Wheeler equation to a
simpler form to extract a Schr\"odinger-like equation. The validity of the
approach is discussed by means of results obtained for the overlap kernel
between HFB states and two-quasi-particle excitations at different
deformations.Comment: 27 pages, 12 figures, submitted to Phys. Rev.
Bessel bridges decomposition with varying dimension. Applications to finance
We consider a class of stochastic processes containing the classical and
well-studied class of Squared Bessel processes. Our model, however, allows the
dimension be a function of the time. We first give some classical results in a
larger context where a time-varying drift term can be added. Then in the
non-drifted case we extend many results already proven in the case of classical
Bessel processes to our context. Our deepest result is a decomposition of the
Bridge process associated to this generalized squared Bessel process, much
similar to the much celebrated result of J. Pitman and M. Yor. On a more
practical point of view, we give a methodology to compute the Laplace transform
of additive functionals of our process and the associated bridge. This permits
in particular to get directly access to the joint distribution of the value at
t of the process and its integral. We finally give some financial applications
to illustrate the panel of applications of our results
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