790 research outputs found
Low-lying isovector monopole resonances
The mass difference between the even-even isobaric nuclei having the valence
nucleons on the same degenerate level is attributed to a Josephson-type
interaction between pairs of protons and pairs of neutrons. This interaction
can be understood as an isospin symmetry-breaking mean field for a
four-particle interaction separable in the two particles-two holes channel. The
strength of this mean field is estimated within an o(5) algebraic model, by
using the experimental value of the inertial parameter for the collective
isorotation induced by the breaking of the isospin symmetry. In superfluid
nuclei, the presumed interaction between the proton and neutron condensates
leads to coupled oscillations of the BCS gauge angles, which should appear in
the excitation spectrum as low-lying isovector monopole resonances.Comment: 16 pages/LaTex + 1 PostScript figure; related to cond-mat/9904242,
math-ph/000500
Number of Spin States of Identical Particles
In this paper we study the enumeration of number (denoted as ) of spin
states for fermions in a single- shell and bosons with spin . We show
that can be enumerated by the reduction from SU to SO(3). New
regularities of are discerned.Comment: 3 pages, no figures. to be publishe
-pairing interaction, number of states, and nine- sum rules of four identical particles
In this paper we study -pairing Hamiltonian and find that the sum of
eigenvalues of spin states equals sum of norm matrix elements within the
pair basis for four identical particles such as four fermions in a single-
shell or four bosons with spin . We relate number of states to sum rules of
nine- coefficients. We obtained sum rules for nine- coefficients
summing
over (1) even and , (2) even and odd , (3) odd and odd ,
and (4) both even and odd , where is a half integer and is an
integer.Comment: 6 pages, no figure, updated version, to be published. Physical Review
C, in pres
Cluster sum rules for three-body systems with angular-momentum dependent interactions
We derive general expressions for non-energy weighted and energy-weighted
cluster sum rules for systems of three charged particles. The interferences
between pairs of particles are found to play a substantial role. The
energy-weighted sum rule is usually determined by the kinetic energy operator,
but we demonstrate that it has similar additional contributions from the
angular momentum and parity dependence of two- and three-body potentials
frequently used in three-body calculations. The importance of the different
contributions is illustrated with the dipole excitations in He. The results
are compared with the available experimental data.Comment: 11 pages, 3 figures, 2 table
Spin-driven spatial symmetry breaking of spinor condensates in a double-well
The properties of an F=1 spinor Bose-Einstein condensate trapped in a
double-well potential are discussed using both a mean-field two-mode approach
and a simplified two-site Bose-Hubbard Hamiltonian. We focus in the region of
phase space in which spin effects lead to a symmetry breaking of the system,
favoring the spatial localization of the condensate in one well. To model this
transition we derive, using perturbation theory, an effective Hamiltonian that
describes N/2 spin singlets confined in a double-well potential.Comment: 12 pages, 5 figure
Configuration mixing calculation for complete low-lying spectra with the mean-field Hamiltonian
We propose a new theoretical approach to ground and low-energy excited states
of nuclei extending the nuclear mean-field theory. It consists of three steps:
stochastic preparation of many Slater determinants, the parity and angular
momentum projection, and diagonalization of the generalized eigenvalue
problems. The Slater determinants are constructed in the three-dimensional
Cartesian coordinate representation capable of describing arbitrary shape of
nuclei. We examine feasibility and usefulness of the method by applying the
method with the BKN interaction to light 4N-nuclei, 12C, 16O, and 20Ne. We
discuss difficulties of keeping linear independence for basis states projected
on good parity and angular momentum and present a possible prescription.Comment: 12 pages, revtex
Equivalent Photon Approach to Simultaneous Excitation in Heavy Ion Collision
We apply the Equivalent Photon Approximation to calculate cross sections for
the simultaneous excitation of two heavy ions in relativistic collisions. We
study especially the excitation of two nuclei to a 1- - state and show that the
equations are symmetric with respect to both ions. We also examine the limit in
which the excitation energy of one of the nuclei goes to zero, which gives the
elastic case. Finally a few remarks about the limits of this approach are made.Comment: 9 pages REVTex, 4 Figures included, see also
http://www.phys.washington.edu/~hencken
On an Alternative Parametrization for the Theory of Complex Spectra
The purpose of this letter is threefold : (i) to derive, in the framework of
a new parametrization, some compact formulas of energy averages for the
electrostatic interaction within an (nl)N configuration, (ii) to describe a new
generating function for obtaining the number of states with a given spin
angular momentum in an (nl)N configuration, and (iii) to report some apparently
new sum rules, actually a by-product of (i), for SU(2) > U(1) coupling
coefficients.Comment: Published in Physics Letters A 147, 417-422 (1990
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