2,835 research outputs found
Analysis of previous microscopic calculations for second state in C in terms of 3-alpha particle Bose-condensed state
The wave function of the second state of C which was obtained
long time ago by solving the microscopic 3 problem is shown to be
almost completely equivalent to the wave function of the 3 condensed
state which has been proposed recently by the present authors. This equivalence
of the wave functions is shown to hold in two cases where different effective
two-nucleon forces are adopted. This finding gives strong support for
interpreting the second state of C which is the key state for the
synthesis of C in stars ('Hoyle' state), and which is one of the typical
mysterious states in light nuclei, as a gas-like structure of three
particles, Bose-condensed into an identical s-wave function.Comment: revtex, 5 pages, 2 figures, submitted to Phys. Rev.
Alpha cluster condensation in 12C and 16O
A new -cluster wave function is proposed which is of the
-particle condensate type. Applications to C and O show
that states of low density close to the 3 resp. 4 -particle threshold
in both nuclei are possibly of this kind. It is conjectured that all
self-conjugate 4 nuclei may show similar features.Comment: 4 pages, 2 tables, 2 figure
Neutron scattering study of magnetic ordering and excitations in the ternary rare-earth diborocarbide Ce^{11}B_2C_2
Neutron scattering experiments have been performed on the ternary rare-earth
diborocarbide CeBC. The powder diffraction experiment confirms
formation of a long-range magnetic order at K, where a
sinusoidally modulated structure is realized with the modulation vector . Inelastic excitation spectra in the
paramagnetic phase comprise significantly broad quasielastic and inelastic
peaks centered at and 65 meV.
Crystalline-electric-field (CEF) analysis satisfactorily reproduces the
observed spectra, confirming their CEF origin. The broadness of the
quasielastic peak indicates strong spin fluctuations due to coupling between
localized spins and conduction electrons in the paramagnetic phase. A
prominent feature is suppression of the quasielastic fluctuations, and
concomitant growth of a sharp inelastic peak in a low energy region below
. This suggests dissociation of the conduction and localized
electrons on ordering, and contrasts the presently observed incommensurate
phase with spin-density-wave order frequently seen in heavy fermion compounds,
such as Ce(RuLa)Si.Comment: accepted for publication in Phys. Rev.
Doping-Dependent and Orbital-Dependent Band Renormalization in Ba(Fe_1-xCo_x)_2As_2 Superconductors
Angle resolved photoemission spectroscopy of Ba(Fe1-xCox)2As2 (x = 0.06,
0.14, and 0.24) shows that the width of the Fe 3d yz/zx hole band depends on
the doping level. In contrast, the Fe 3d x^2-y^2 and 3z^2-r^2 bands are rigid
and shifted by the Co doping. The Fe 3d yz/zx hole band is flattened at the
optimal doping level x = 0.06, indicating that the band renormalization of the
Fe 3d yz/zx band correlates with the enhancement of the superconducting
transition temperature. The orbital-dependent and doping-dependent band
renormalization indicates that the fluctuations responsible for the
superconductivity is deeply related to the Fe 3d orbital degeneracy.Comment: 5 pages, 4 figure
FUNDAMENTAL STUDY ON MODIFICATION PROCESS OF DESIGN PLAN FOR COMPUTER-AIDED PRODUCT DESIGN CONSIDERING WAYS OF USAGE
Globalization in industry has increased the number of troubles caused by using products in unexpected ways. It is important to avoid such troubles in advance by performing product design considering various ways of usage. To achieve this, it is necessary to predict various ways of usage, to detect troubles which may occur by using the product in those ways and to modify the current design plan so that those troubles are avoided. A set of methods are developed based on Petri net modeling of design plan for computer support of the former two processes. The last process basically depends on creativity and knowledge of designers. However, if there are patterns of modification, it would be possible to help designers to modify design plans with computers by exploiting those patterns. This research aims at finding patterns of modification from cases of modification of design plan in actual design. Definition of pattern of modification was discussed and given as a combination of the reason, the objective and the way of modification. 200 patterns were then obtained by classification of each of the three items. It was found that many cases of modification in actual design fit 9 of the 200 patterns. It is possible that those 9 patterns can be exploited for computer support of modification process
A Method for Flexible Job-Shop Scheduling using Genetic Algorithm
This paper focused on solving a flexible job-shop scheduling problem. Because this problem is known as NP-hard, methods using meta-heuristics especially genetic algorithm (GA) have been actively proposed. Although it is possible to obtain solutions of large problems in a reasonable time by those methods, the quality of the solutions decreases as the scale of the problem increases. Hence, taking advantage of knowledge included in heuristic dispatching rules in the optimization by GA was proposed, and its effectiveness was proven. However, in this method, the two kinds of selection required in flexible job-shop production, machine selection and job selection, were carried out sequentially. Because this may result in insufficient search of the solution space, this paper provided a method using GA in which those two selections were performed at once. The method was applied to an example and it was shown that better solutions could be obtained
cluster structure in B
The cluster structures of the excited states in B are studied by
analyzing the isoscalar monopole and quadrupole strengths in the
B(,) reaction at MeV. The excitation strengths are
compared with the predictions by the shell-model and antisymmetrized
molecular-dynamics (AMD) calculations. It is found that the large monopole
strength for the state at MeV is well described by the AMD
calculation and is an evidence for a developed cluster structure.Comment: Revised according to the referees' comment
Single Crystal Growth and Characterization of the Iron-Based Superconductor KFe2As2 Synthesized by KAs Flux Method
Centimeter sized platelet single crystals of KFe2As2 were grown using a
self-flux method. An encapsulation technique using commercial stainless steel
container allowed the stable crystal growth lasting for more than 2 weeks.
Ternary K-Fe-As systems with various starting compositions were examined to
determine the optimal growth conditions. Employment of KAs flux led to the
growth of large single crystals with the typical size of as large as 15 mm x 10
mm x 0.4 mm. The grown crystals exhibit sharp superconducting transition at 3.4
K with the transition width 0.2 K, as well as the very large residual
resistivity ratio exceeding 450, evidencing the good sample quality.Comment: 4 pages, 6 Postscript figure
Cluster structure in stable and unstable nuclei
Cluster structure in stable and unstable nuclei has been studied. We report
recent developments of theoretical studies on cluster aspect, which is
essential for structure study of light unstable nuclei. We discuss negative
parity bands in even-even Be and Ne isotopes and show the importance of cluster
aspect. Three-body cluster structure and cluster crystallization are also
introduced. It was found that the coexistence of cluster and mean-field aspect
brings a variety of structures to unstable nuclei.Comment: 6 pages, 3 figures, submitted to Euro. Phys. J.
Cooling atomic motion with quantum interference
We theoretically investigate the quantum dynamics of the center of mass of
trapped atoms, whose internal degrees of freedom are driven in a
-shaped configuration with the lasers tuned at two-photon resonance.
In the Lamb-Dicke regime, when the motional wave packet is well localized over
the laser wavelenght, transient coherent population trapping occurs, cancelling
transitions at the laser frequency. In this limit the motion can be efficiently
cooled to the ground state of the trapping potential. We derive an equation for
the center-of-mass motion by adiabatically eliminating the internal degrees of
freedom. This treatment provides the theoretical background of the scheme
presented in [G. Morigi {\it et al}, Phys. Rev. Lett. {\bf 85}, 4458 (2000)]
and implemented in [C.F. Roos {\it et al}, Phys. Rev. Lett. {\bf 85}, 5547
(2000)]. We discuss the physical mechanisms determining the dynamics and
identify new parameters regimes, where cooling is efficient. We discuss
implementations of the scheme to cases where the trapping potential is not
harmonic.Comment: 11 pages, 3 figure
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