19,831 research outputs found
Theoretical study of the decay-out spin of superdeformed bands in the Dy and Hg regions
Decay of the superdeformed bands have been studied mainly concentrating upon
the decay-out spin, which is sensitive to the tunneling probability between the
super- and normal-deformed wells. Although the basic features are well
understood by the calculations, it is difficult to precisely reproduce the
decay-out spins in some cases. Comparison of the systematic calculations with
experimental data reveals that values of the calculated decay-out spins scatter
more broadly around the average value in both the 150 and 190
regions, which reflects the variety of calculated tunneling probability in each
band.Comment: 6 pages 4 figures (30 PS files). To appear in Proc. of NS2000
(Nuclear Structure 2000) conf., at MSU, 15-19 Aug., 200
High-K Precession modes: Axially symmetric limit of wobbling motion
The rotational band built on the high-K multi-quasiparticle state can be
interpreted as a multi-phonon band of the precession mode, which represents the
precessional rotation about the axis perpendicular to the direction of the
intrinsic angular momentum. By using the axially symmetric limit of the
random-phase-approximation (RPA) formalism developed for the nuclear wobbling
motion, we study the properties of the precession modes in W; the
excitation energies, B(E2) and B(M1) values. We show that the excitations of
such a specific type of rotation can be well described by the RPA formalism,
which gives a new insight to understand the wobbling motion in the triaxial
superdeformed nuclei from a microscopic view point.Comment: 14 pages, 8 figures (Spelling of the authors name was wrong at the
first upload, so it is corrected
Cluster Property and Robustness of Ground States of Interacting Many Bosons
We study spatial correlation functions of local operators of interacting many
bosons confined in a box of a large, but volume V, for various `ground states'
whose energy densities are almost degenerate. The ground states include the
coherent state of interacting bosons (CSIB), the number state of interacting
bosons (NSIB), and the number-phase squeezed state of interacting bosons, which
interpolates between the CSIB and NSIB. It was shown previously that only the
CSIB is robust (i.e., does not decohere for a macroscopically long time)
against the leakage of bosons into an environment. We show that for the CSIB
the spatial correlation of any local operators A(r) and B(r') (which are
localized around r and r', respectively) vanishes as |r - r' | \sim V^{1/3} \to
\infty, i.e., the CSIB has the `cluster property.' In contrast, the other
ground states do not possess the cluster property. Therefore, we have
successfully shown that the robust state has the cluster property. This ensures
the consistency of the field theory of bosons with macroscopic theories.Comment: We have replaced the manuscript in order to update the reference list
and to fix typos. (5 pages, no figures) In the final manuscript, a few
sentences have added for more detailed explanation. Journal PDF at
http://jpsj.jps.or.jp/journal/JPSJ-71-1.htm
Stability of quantum states of finite macroscopic systems against classical noises, perturbations from environments, and local measurements
We study the stability of quantum states of macroscopic systems of finite
volume V, against weak classical noises (WCNs), weak perturbations from
environments (WPEs), and local measurements (LMs). We say that a pure state is
`fragile' if its decoherence rate is anomalously great, and `stable against
LMs' if the result of a LM is not affected by another LM at a distant point. By
making full use of the locality and huge degrees of freedom, we show the
following: (i) If square fluctuation of every additive operator is O(V) or less
for a pure state, then it is not fragile in any WCNs or WPEs. (ii) If square
fluctuations of some additive operators are O(V^2) for a pure state, then it is
fragile in some WCNs or WPEs. (iii) If a state (pure or mixed) has the `cluster
property,' then it is stable against LMs, and vice versa. These results have
many applications, among which we discuss the mechanism of symmetry breaking in
finite systems.Comment: 6 pages, no figure.Proof of the theorem is described in the revised
manuscrip
Spreading Width for Decay out of a Superdeformed Band
The attenuation factor F responsible for the decay out of a superdeformed
(SD) band is calculated with the help of a statistical model. This factor is
given by 1/F = (1 + Gamma(down) / Gamma(S)). Here, Gamma(S) is the width for
the collective E2 transition within the superdeformed band, and Gamma(down) is
the spreading width which describes the mixing between a state in the SD band
and the normally deformed (ND) states of equal spin. The attenuation factor F
is independent of the statistical E1 decay widths Gamma(N) of the ND states
provided that the Gamma(N) are much larger than both Gamma(down) and Gamma(S).
This condition is generically met. Previously measured values of F are used to
determine Gamma(down).Comment: Submitted to Physical Review Letter
An AC electric trap for ground-state molecules
We here report on the realization of an electrodynamic trap, capable of
trapping neutral atoms and molecules in both low-field and high-field seeking
states. Confinement in three dimensions is achieved by switching between two
electric field configurations that have a saddle-point at the center of the
trap, i.e., by alternating a focusing and a defocusing force in each direction.
AC trapping of 15ND3 molecules is experimentally demonstrated, and the
stability of the trap is studied as a function of the switching frequency. A 1
mK sample of 15ND3 molecules in the high-field seeking component of the
|J,K>=|1,1> level, the ground-state of para-ammonia, is trapped in a volume of
about 1 mm^3
Shape coexistence in Lead isotopes in the interacting boson model with Gogny energy density functional
We investigate the emergence and evolution of shape coexistence in the
neutron-deficient Lead isotopes within the interacting boson model (IBM) plus
configuration mixing with microscopic input based on the Gogny energy density
functional (EDF). The microscopic potential energy surface obtained from the
constrained self-consistent Hartree-Fock-Bogoliubov method employing the
Gogny-D1M EDF is mapped onto the coherent-state expectation value of the
configuration-mixing IBM Hamiltonian. In this way, the parameters of the IBM
Hamiltonian are fixed for each of the three relevant configurations (spherical,
prolate and oblate) associated to the mean field minima. Subsequent
diagonalization of the Hamiltonian provides the excitation energy of the
low-lying states and transition strengths among them. The model predictions for
the level energies and evolving shape coexistence in the considered
Lead chain are consistent both with experiment and with the indications of the
Gogny-EDF energy surfaces.Comment: 12 pages, 6 figures, 1 tabl
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