2,648 research outputs found
Classification of states of single- fermions with -pairing interaction
In this paper we show that a system of three fermions is exactly solvable for
the case of a single- in the presence of an angular momentum- pairing
interaction. On the basis of the solutions for this system, we obtain new sum
rules for six- symbols. It is also found that the "non-integer" eigenvalues
of three fermions with angular momentum around the maximum appear as
"non-integer" eigenvalues of four fermions when is around (or larger than)
and the Hamiltonian contains only an interaction between pairs of
fermions coupled to spin . This pattern is also found in
five and six fermion systems. A boson system with spin exhibits a similar
pattern.Comment: to be published in Physical Review
General pairing interactions and pair truncation approximations for fermions in a single-j shell
We investigate Hamiltonians with attractive interactions between pairs of
fermions coupled to angular momentum J. We show that pairs with spin J are
reasonable building blocks for the low-lying states. For systems with only a J
= Jmax pairing interaction, eigenvalues are found to be approximately integers
for a large array of states, in particular for those with total angular momenta
I le 2j. For I=0 eigenstates of four fermions in a single-j shell we show that
there is only one non-zero eigenvalue. We address these observations using the
nucleon pair approximation of the shell model and relate our results with a
number of currently interesting problems.Comment: a latex text file and 2 figures, to be publishe
One-pion exchange current corrections for nuclear magnetic moments in relativistic mean field theory
The one-pion exchange current corrections to isoscalar and isovector magnetic
moments of double-closed shell nuclei plus and minus one nucleon with
and 41 have been studied in the relativistic mean field (RMF)
theory and compared with previous relativistic and non-relativistic results. It
has been found that the one-pion exchange current gives a negligible
contribution to the isoscalar magnetic moments but a significant correction to
the isovector ones. However, the one-pion exchange current doesn't improve the
description of nuclear isovector magnetic moments for the concerned nuclei.Comment: 9 pages, 1 figure, 3 table
Analytic approach to nuclear rotational states: The role of spin - A minimal model -
We use a simple field theory model to investigate the role of the nucleon
spin for the magnetic sum rules associated with the low-lying collective
scissors mode in deformed nuclei. Various constraints from rotational symmetry
are elucidated and discussed. We put special emphasis on the coupling of the
spin part of the M1 operator to the low lying collective modes, and investigate
how this coupling changes the sum rules.Comment: 15 pages, 4 figure
Chiral Symmetry and N*(1440) -> N pi pi Decay
The N*(1440) -> N pi pi decay is studied by making use of the chiral
reduction formula. This formula suggests a scalar-isoscalar pion-baryon contact
interaction which is absent in the recent study of Hern{\'a}ndez et al. The
contact interaction is introduced into their model, and is found to be
necessary for the simultaneous description of g_{RN pi pi} and the pi-pi and
pi-N invariant mass distributions.Comment: 12 page
Critical-Point Symmetry in a Finite System
At a critical point of a second order phase transition the intrinsic energy
surface is flat and there is no stable minimum value of the deformation.
However, for a finite system, we show that there is an effective deformation
which can describe the dynamics at the critical point. This effective
deformation is determined by minimizing the energy surface after projection
onto the appropriate symmetries. We derive analytic expressions for energies
and quadrupole rates which provide good estimates for these observables at the
critical point.Comment: 12 pages, 2 figures, 2 tables, Phys. Rev. Lett. in pres
Lowest eigenvalue of the nuclear shell model Hamiltonian
In this paper we investigate regular patterns of matrix elements of the
nuclear shell model Hamiltonian , by sorting the diagonal matrix elements
from the smaller to larger values. By using simple plots of non-zero matrix
elements and lowest eigenvalues of artificially constructed "sub-matrices"
of , we propose a new and simple formula which predicts the lowest
eigenvalue with remarkable precisions.Comment: six pages, four figures, Physical Review C, in pres
Residual proton-neutron interactions and the scheme
We investigate the correlation between integrated proton-neutron interactions
obtained by using the up-to-date experimental data of binding energies and the
, the product of valence proton number and valence neutron
number with respect to the nearest doubly closed nucleus. We make corrections
on a previously suggested formula for the integrated proton-neutron
interaction. Our results demonstrate a nice, nearly linear, correlation between
the integrated p-n interaction and , which provides us
with a firm foundation of the applicability of the scheme
to nuclei far from the stability line.Comment: four pages, three figures, Physical Review C, in pres
Joint effect of lattice interaction and potential fluctuation in colossal magnetoresistive manganites
Taking into account both the Jahn-Teller lattice distortion and the on-site
electronic potential fluctuations in the orbital-degenerated double-exchange
model, in which both the core-spin and the lattice distortion are treated
classically, we investigate theoretically the metal-insulator transition (MIT)
in manganites by considering the electronic localization effect. An inverse
matrix method is developed for calculation in which we use the inverse of the
transfer matrix to obtain the localization length. We find that within
reasonable range of parameters, both the lattice effect and the potential
fluctuation are responsible to the occurrence of the MIT. The role of the
orbital configuration is also discussed.Comment: 4 figure
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