Dynamics of two-sign point vortices in two-dimensional circular boundary is examined by numerical simulations with MDGRAPE-2. The vortex system is characterized by the inverse temperature beta as determined from the density of states of the microcanonical ensemble of numerically generated 10(7) states. The massive simulation shows that different configurations appear in the time-asymptotic state depending on the sign of beta. Condensation of the same-sign vortices is observed when beta<0, while the both-sign vortices tend to be uniformly neutralized when beta>0. During the condensation, a part of the vortices gains energy to form clumps (patches), and the other part of the vortices loses energy to keep the total energy constant and mixes with vortices of the other sign. This observation demonstrates a characteristic feature of negative beta states that the system energy concentrates into the clumps of the same-sign vortices.

Abstract. Classical dynamics of two-electron atom and ions H − , He, Li + , Be 2+ , ... in collinear eZe configuration is investigated. We consider the case that the masses of all particles are finite. It is revealed that the mass ratio ξ between nucleus and electron plays an important role for dynamical behaviour of these systems. With the aid of analytical tool and numerical computation, it is shown that thanks to large mass ratio ξ, classical dynamics of these systems is fully chaotic, probably hyperbolic. Experimental manifestation of this finding is also proposed.

The Pollicott-Ruelle resonances for the sawtooth map are investigated. We turn our attention to the parametric dependence of them with respect to the bifurcation parameter K. It is numerically shown that the resonances move in an erratic way if the bifurcation parameter K is supposed to be time. At certain rational values of K, it is observed that some resonances shrink to z=0. In particular, at positive integer values of K which correspond to the Arnold cat map, all resonances except z=1 (i.e., the equilibrium state) shrink to z=0. This peculiar behavior is rigorously proved in the Appendix. In addition, the diffusion coefficient of this map is numerically calculated in a very accurate way by evaluating the leading resonance.

Thermal conduction in a chain of colliding harmonic oscillators, sometimes called the ding-dong model, is investigated. We first argue that this system is equivalent to the Dawson plasma sheet model. Next we show the Lyapunov analysis for this system to characterize its dynamical property. Finally, we reconsider the numerical study of thermal conduction for this system using the Green-Kubo relation and the direct simulation of Fourier law. Both show that thermal conduction is normal in that kappa(N,T) approximately equals N(0), at least, at low temperature in a large system.

We investigate statistical properties of unstable periodic orbits, especially actions for two simple linear maps (p-adic Baker map and sawtooth map). The action of periodic orbits for both maps is written in terms of symbolic dynamics. As a result, the expression of action for both maps becomes a Hamiltonian of one-dimensional spin systems with the exponential-type pair interaction. Numerical work is done for enumerating periodic orbits. It is shown that after symmetry reduction, the dyadic Baker map is close to generic systems, and the p-adic Baker map and sawtooth map with noninteger K are also close to generic systems. For the dyadic Baker map, the trace of the quantum time-evolution operator is semiclassically evaluated by employing the method of Phys. Rev. E 49, R963 (1994). Finally, using the result of this and with a mathematical tool, it is shown that, indeed, the actions of the periodic orbits for the dyadic Baker map with symmetry reduction obey the uniform distribution modulo 1 asymptotically as the period goes to infinity. (c) 2000 American Institute of Physics.