35,580 research outputs found

    QCD color interactions between two quarks

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    We study the QCD color interactions between static two heavy quarks at zero temperature in a quenched SU(3) lattice gauge simulation: in addition to the standard singlet qqˉq\bar{q} potentials, we calculate octet qqˉq\bar{q} potentials, symmetric and antisymmetric qqqq potentials. It is shown that the antisymmetric qqqq channel behaves as a linearly rising potential at large quark separations. We further find that the qqˉq\bar{q} octet and qqqq symmetric channels have the complex dependence on the distance; at short distances they are repulsive forces, while at large distances, they show linearly rising feature. Ratio of string tensions between qqˉq\bar{q} singlet and qqqq antisymmetric potentials is described in terms of the Casimir factor

    Hyperons in nuclear matter

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    The chiral version of the QMC model, in which the effect of gluon and pion exchanges is included self-consistently, is applied to the hyperons in a nuclear medium. The hyperfine interaction due to the gluon exchange plays an important role in the in-medium baryon spectra, while the pion-cloud effect is relatively small. At the quark mean-field level, the Λ\Lambda feels more attractive force than the \Sigma or \Xi in matter.Comment: 9 pages, 6 figure

    Seismic Risk Evaluation of R.C. Buildings in Japan Designated in Accordance with the 1990 AIJ Guidelines

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    National Science Foundation Grant BCS 91-06390Kajima Foundatio

    Disturbances of both cometary and Earth's magnetospheres excited by single solar flares

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    In the solar wind a comet plays the role of a windvane that moves three-dimensionally in the heliomagnetosphere. Among the solar systems bodies, only comets have a wide range of inclination angles of their orbital planes to the ecliptic plane ranging from 0 to 90 deg. Therefore, observations of cometary plasma tails are useful in probing the heliomagnetospheric conditions in the high heliolatitudinal region. A comet can be compared to a polar-orbiting probe encircling the Sun. We will introduce two rare cases in which the magnetospheres of both the comet and the Earth are disturbed by a single solar flare

    The energy dependence of the πN\pi N amplitude and the three-nucleon interaction

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    By calculating the contribution of the ππ\pi-\pi three-body force to the three-nucleon binding energy in terms of the πN\pi N amplitude using perturbation theory, we are able to determine the importance of the energy dependence and the contribution of the different partial waves of the πN\pi N amplitude to the three-nucleon force. A separable representation of the non-pole πN\pi N amplitude allows us to write the three-nucleon force in terms of the amplitude for NNNNNN\rightarrow NN^*, propagation of the NNNNNN^* system, and the amplitude for NNNNNN^*\rightarrow NN, with NN^* being the πN\pi N quasi-particle amplitude in a given state. The division of the πN\pi N amplitude into a pole and non-pole gives a procedure for the determination of the πNN\pi NN form factor within the model. The total contribution of the three-body force to the binding energy of the triton for the separable approximation to the Paris nucleon-nucleon potential (PEST) is found to be very small mainly as a result of the energy dependence of the πN\pi N amplitude, the cancellation between the SS- and PP-wave πN\pi N amplitudes, and the soft πNN\pi NN form factor.Comment: RevTex file, 36 pages, 10 figures available from authors: [email protected]