5,350 research outputs found
The Write Approach to Mathematics or How I Found the Middle Way
Revising a course is a multifaceted process. Often, reform efforts are focused on a particular aspect, that of inquiry-based collaborative learning. This article discusses the implementation of another aspect of the reform of a course for pre-service elementary teachers: the use of journals and writing exercises for evaluation and assessment. The evolution of this particular reform is traced, with emphasis on the reactions of students and faculty, the issues raised by these reactions, and the solution and resolution attained by the author is outlined
Configuration mixing of angular-momentum projected triaxial relativistic mean-field wave functions. II. Microscopic analysis of low-lying states in magnesium isotopes
The recently developed structure model that uses the generator coordinate
method to perform configuration mixing of angular-momentum projected wave
functions, generated by constrained self-consistent relativistic mean-field
calculations for triaxial shapes (3DAMP+GCM), is applied in a systematic study
of ground states and low-energy collective states in the even-even magnesium
isotopes Mg. Results obtained using a relativistic point-coupling
nucleon-nucleon effective interaction in the particle-hole channel, and a
density-independent -interaction in the pairing channel, are compared
to data and with previous axial 1DAMP+GCM calculations, both with a
relativistic density functional and the non-relativistic Gogny force. The
effects of the inclusion of triaxial degrees of freedom on the low-energy
spectra and E2 transitions of magnesium isotopes are examined.Comment: 28 pages, 11 figures and 1 tabl
Perturbative HFB model for many-body pairing correlations
We develop a perturbative model to treat the off-diagonal components in the
Hartree-Fock-Bogoliubov (HFB) transformation matrix, which are neglected in the
BCS approximation. Applying the perturbative model to a weakly bound nucleus
Ni, it is shown that the perturbative approach reproduces well the
solutions of the HFB method both for the quasi-particle energies and the radial
dependence of quasi-particle wave functions. We find that the non-resonant part
of the continuum single-particle state can acquire an appreciable occupation
probability when there exists a weakly bound state close to the Fermi surface.
This result originates from the strong coupling between the continuum particle
state and the weakly bound state, and is absent in the BCS approximation. The
limitation of the BCS approximation is pointed out in comparison with the HFB
and the present perturbative model.Comment: 6 pages, 5 eps figure
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
Nuclear fission in covariant density functional theory
The current status of the application of covariant density functional theory
to microscopic description of nuclear fission with main emphasis on superheavy
nuclei (SHN) is reviewed. The softness of SHN in the triaxial plane leads to an
emergence of several competing fission pathes in the region of the inner
fission barrier in some of these nuclei. The outer fission barriers of SHN are
considerably affected both by triaxiality and octupole deformation.Comment: 6 pages, 4 figures, will be published in European Physical Journal,
Web of Conferences, (Proceedings of Fifth International Workshop on Nuclear
fission and Fission-Product Spectroscopy
Static observables of relativistic three-fermion systems with instantaneous interactions
We show that static properties like the charge radius and the magnetic moment
of relativistic three-fermion bound states with instantaneous interactions can
be formulated as expectation values with respect to intrinsically defined
wavefunctions. The resulting operators can be given a natural physical
interpretation in accordance with relativistic covariance. We also indicate how
the formalism may be generalized to arbitrary moments. The method is applied to
the computation of static baryon properties with numerical results for the
nucleon charge radii and the baryon octet magnetic moments. In addition we make
predictions for the magnetic moments of some selected nucleon resonances and
discuss the decomposition of the nucleon magnetic moments in contributions of
spin and angular momentum, as well as the evolution of these contributions with
decreasing quark mass.Comment: 13 pages, including 2 figures and 3 tables, submitted to Eur.Phys.J.
Pairing correlations in nuclei on the neutron-drip line
Paring correlations in weakly bound nuclei on the edge of neutron drip line
is studied by using a three-body model. A density-dependent contact interaction
is employed to calculate the ground state of halo nuclei He and
Li, as well as a skin nucleus O. Dipole excitations in these
nuclei are also studied within the same model. We point out that the di-neutron
type correlation plays a dominant role in the halo nuclei He and
Li having the coupled spin of the two neutrons =0, while the
correlation similar to the BCS type is important in O. Contributions of
the spin =1 and S=0 configurations are separately discussed in the low
energy dipole excitations.Comment: 6 pages, 12 eps figure
Pairing in the Framework of the Unitary Correlation Operator Method (UCOM): Hartree-Fock-Bogoliubov Calculations
In this first in a series of articles, we apply effective interactions
derived by the Unitary Correlation Operator Method (UCOM) to the description of
open-shell nuclei, using a self-consistent Hartree-Fock-Bogoliubov framework to
account for pairing correlations. To disentangle the particle-hole and
particle-particle channels and assess the pairing properties of \VUCOM, we
consider hybrid calculations using the phenomenological Gogny D1S interaction
to derive the particle-hole mean field. In the main part of this article, we
perform calculations of the tin isotopic chain using \VUCOM in both the
particle-hole and particle-particle channels. We study the interplay of both
channels, and discuss the impact of non-central and non-local terms in
realistic interactions as well as the frequently used restriction of pairing
interactions to the partial wave. The treatment of the center-of-mass
motion and its effect on theoretical pairing gaps is assessed independently of
the used interactions.Comment: 14 pages, 10 figures, to appear in Phys. Rev. C, title modified
accordingl
Nuclear Excitations Described by Randomly Selected Multiple Slater Determinants
We propose a new stochastic method to describe low-lying excited states of
finite nuclei superposing multiple Slater determinants without assuming
generator coordinates a priori. We examine accuracy of our method by using
simple BKN interaction.Comment: Talk at International Symposium on Correlation Dynamics in Nuclei,
Tokyo, Japan, 31 Jan.-- 4 Feb. 200
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