Proposal to observe the strong Van der Waals force in e+\bar{e} -> 2 \pi

Large discrepancy of the p-wave phase shift data $\delta_{1}(\nu)$ of the $\pi$-$\pi$ scattering from those of the dispersion calculation is pointed out. In order to determine which is correct, the pion form factor $F_{\pi}(\nu)$, which is the second source of information of the phase shift $\delta_{1}(\nu)$, is used. It is found that the phase shift obtained from the dispersion is not compatible with the data of the pion form factor. What is wrong with the dispersion calculation, is considered.Comment: 7 pages, 7eps figure

Generalized Optimal Velocity Model for Traffic Flow

A generalized optimal velocity model is analyzed, where the optimal velocity function depends not only on the headway of each car but also the headway of the immediately preceding one. The stability condition of the model is derived by considering a small perturbation around the homogeneous flow solution. The effect of the generalized optimal velocity function is also confirmed with numerical simulation, by examining the hysteresis loop in the headway-velocity phase space, and the relation between flow and density of cars. In the model with a specific parameter choice, it is found that an intermediate state appears for the movement of cars, where the car keeps a certain velocity though the headway is short or long. This phenomenon is different from the ordinary stop-and-go state.Comment: 13 pages, 9 figure

3D Finite Volume Simulation of Accretion Discs with Spiral Shocks

We perform 2D and 3D numerical simulations of an accretion disc in a close binary system using the Simplified Flux vector Splitting (SFS) finite volume method. In our calculations, gas is assumed to be the ideal one, and we calculate the cases with gamma=1.01, 1.05, 1.1 and 1.2. The mass ratio of the mass losing star to the mass accreting star is unity. Our results show that spiral shocks are formed on the accretion disc in all cases. In 2D calculations we find that the smaller gamma is, the more tightly the spiral winds. We observe this trend in 3D calculations as well in somewhat weaker sense.Comment: 2 pages, LaTeX with 2 ps figures using crckapb.sty. To appear in the Proceedings of Numerical Astrophysics 1998, Tokyo, Japan, 10-13 March, 1998, eds. S. M. Miyama, K. Tomisaka and T. Hanawa (Kluwer Academic Publishers