2,413 research outputs found
Excitation Spectrum in the Friedberg-Lee Model
The excitation spectrum of the nucleon with the spin 1/2 is examined by using
the Friedberg-Lee model containing the constituent quark and the scalar meson.
An appropriate way of quantization for the non-linear meson field is employed
by taking account of the non-topological soliton existed in the classical
level.
Our model space for the nucleon resonances includes the three-quark plus
one-meson state in addition to the pure three-quark state.
The excitation spectrum in this model space shows that the positive parity
state appears as the first excited state associated with the 0s-excitation of
the scalar meson.
The meson excitation also generates the additional negative parity state
apart from the well-known 0p-excitation of the quark.Comment: 12 pages including 4 figures(eps). Prog. Theor. Phys. in pres
Nucleon resonances in the constituent quark model with chiral symmetry
The mass spectra of nucleon resonances with spin 1/2, 3/2, and 5/2 are
systematically studied in the constituent quark model with meson-quark
coupling, which is inspired by the spontaneous breaking of chiral symmetry of
QCD.
The meson-quark coupling gives rise not only to the one-meson-exchange
potential between quarks but also to the self-energy of baryon resonances due
to the existence of meson-baryon decay channels.
The two contributions are consistently taken into account in the calculation.
The gross properties of the nucleon resonance spectra are reproduced fairly
well although the predicted mass of N(1440) is too high.Comment: 14 pages, 6 figures, Late
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
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
Development of a task-level robot programming and simulation system
An ongoing project in developing a Task-Level Robot Programming and Simulation System (TARPS) is discussed. The objective of this approach is to design a generic TARPS that can be used in a variety of applications. Many robotic applications require off-line programming, and a TARPS is very useful in such applications. Task level programming is object centered in that the user specifies tasks to be performed instead of robot paths. Graphics simulation provides greater flexibility and also avoids costly machine setup and possible damage. A TARPS has three major modules: world model, task planner and task simulator. The system architecture, design issues and some preliminary results are given
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