1,375 research outputs found
Effective-Mass Klein-Gordon-Yukawa Problem for Bound and Scattering States
Bound and scattering state solutions of the effective-mass Klein-Gordon
equation are obtained for the Yukawa potential with any angular momentum
. Energy eigenvalues, normalized wave functions and scattering phase
shifts are calculated as well as for the constant mass case. Bound state
solutions of the Coulomb potential are also studied as a limiting case.
Analytical and numerical results are compared with the ones obtained before.Comment: 13 pages, 1 figur
Studying Gaugino Mass in Semi-Direct Gauge Mediation
We study gaugino mass generation in the context of semi-direct gauge
mediation models, where the messengers are charged under both the hidden sector
and the standard model gauge groups while they do not play important roles in
dynamical supersymmetry breaking. We clarify the cancellation of the leading
contributions of the supersymmetry breaking effects to the gaugino mass in this
class of models in terms of the macroscopic effective theory of the hidden
sector dynamics. We also consider how to retrofit the model so that we obtain
the non-vanishing leading contribution to the gaugino mass.Comment: 14 page
Hadron-hadron interaction from SU(2) lattice QCD
We evaluate interhadron interactions in two-color lattice QCD from
Bethe-Salpeter amplitudes on the Euclidean lattice. The simulations are
performed in quenched SU(2) QCD with the plaquette gauge action at and the Wilson quark action. We concentrate on S-wave scattering states
of two scalar diquarks. Evaluating different flavor combinations with various
quark masses, we try to find out the ingredients in hadronic interactions.
Between two scalar diquarks (, the lightest baryon in SU(2)
system), we observe repulsion in short-range region, even though present quark
masses are not very light. We define and evaluate the "quark-exchange part" in
the interaction, which is induced by adding quark-exchange diagrams, or
equivalently, by introducing Pauli blocking among some of quarks. The repulsive
force in short-distance region arises only from the "quark-exchange part", and
disappears when quark-exchange diagrams are omitted. We find that the strength
of repulsion grows in light quark-mass regime and its quark-mass dependence is
similar to or slightly stronger than that of the color-magnetic interaction by
one-gluon-exchange (OGE) processes. It is qualitatively consistent with the
constituent-quark model picture that a color-magnetic interaction among quarks
is the origin of repulsion. We also find a universal long-range attractive
force, which enters in any flavor channels of two scalar diquarks and whose
interaction range and strength are quark-mass independent. The weak quark-mass
dependence of interaction ranges in each component implies that meson-exchange
contributions are small and subdominant, and the other contributions, {\it ex.}
flavor exchange processes, color-Coulomb or color-magnetic interactions, are
considered to be predominant, in the quark-mass range we evaluated.Comment: 14 pages, 20 figure
Nuclear Force from Lattice QCD
The first lattice QCD result on the nuclear force (the NN potential) is
presented in the quenched level. The standard Wilson gauge action and the
standard Wilson quark action are employed on the lattice of the size 16^3\times
24 with the gauge coupling beta=5.7 and the hopping parameter kappa=0.1665. To
obtain the NN potential, we adopt a method recently proposed by CP-PACS
collaboration to study the pi pi scattering phase shift. It turns out that this
method provides the NN potentials which are faithful to those obtained in the
analysis of NN scattering data. By identifying the equal-time Bethe-Salpeter
wave function with the Schroedinger wave function for the two nucleon system,
the NN potential is reconstructed so that the wave function satisfies the
time-independent Schroedinger equation. In this report, we restrict ourselves
to the J^P=0^+ and I=1 channel, which enables us to pick up unambiguously the
``central'' NN potential V_{central}(r). The resulting potential is seen to
posses a clear repulsive core of about 500 MeV at short distance (r < 0.5 fm).
Although the attraction in the intermediate and long distance regions is still
missing in the present lattice set-up, our method is appeared to be quite
promising in reconstructing the NN potential with lattice QCD.Comment: A talk given at the XXIV International Symposium on Lattice Field
Theory (Lattice2006), Tucson, Arizona, USA, July 23-28, 2006, 3 figures,
7page
Handling of a constrained flexible object by a robot
科研費報告書収録論文(課題番号:07455416・基盤研究(B)(2)・H7~H9/研究代表者:内山, 勝/フレキシブル双腕ロボットの協調制御に関する研究
Cooperative control of a vibrating flexible object by a rigid dual-arm robot
科研費報告書収録論文(課題番号:07455416・基盤研究(B)(2)・H7~H9/研究代表者:内山, 勝/フレキシブル双腕ロボットの協調制御に関する研究
A rejection-free Monte Carlo method for the hard-disk system
We construct a rejection-free Monte Carlo method for the hard-disk system.
Rejection-free Monte Carlo methods preserve the time-evolution behavior of the
standard Monte Carlo method, and this relationship is confirmed for our method
by observing nonequilibrium relaxation of a bond-orientational order parameter.
The rejection-free method gives a greater computational efficiency than the
standard method at high densities. The rejection free method is implemented in
a shrewd manner using optimization methods to calculate a rejection probability
and to update the system. This method should allow an efficient study of the
dynamics of two-dimensional solids at high density.Comment: 8 pages, 9 figures. This paper has been combined into the
cond-mat/0508652, and published in Phys. Rev.
Solvable Optimal Velocity Models and Asymptotic Trajectory
In the Optimal Velocity Model proposed as a new version of Car Following
Model, it has been found that a congested flow is generated spontaneously from
a homogeneous flow for a certain range of the traffic density. A
well-established congested flow obtained in a numerical simulation shows a
remarkable repetitive property such that the velocity of a vehicle evolves
exactly in the same way as that of its preceding one except a time delay .
This leads to a global pattern formation in time development of vehicles'
motion, and gives rise to a closed trajectory on -
(headway-velocity) plane connecting congested and free flow points. To obtain
the closed trajectory analytically, we propose a new approach to the pattern
formation, which makes it possible to reduce the coupled car following
equations to a single difference-differential equation (Rondo equation). To
demonstrate our approach, we employ a class of linear models which are exactly
solvable. We also introduce the concept of ``asymptotic trajectory'' to
determine and (the backward velocity of the pattern), the global
parameters associated with vehicles' collective motion in a congested flow, in
terms of parameters such as the sensitivity , which appeared in the original
coupled equations.Comment: 25 pages, 15 eps figures, LaTe
Recent advances in the theory of nuclear forces
After a brief historical review, we present recent progress in our
understanding of nuclear forces in terms of chiral effective field theory.Comment: 6 pages, 2 figures; talk at International Symposium on Correlations
Dynamics in Nuclei, University of Tokyo, Japan, 31 January-4 February, 200
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