Mitsuru Shibayama

We consider the planar three-body problem with generalized potentials. Some nonintegrability results for these systems have been obtained by analyzing the variational equations along homothetic solutions. But we cannot apply it to several exceptional cases. For example, in the case of inverse-square potentials, the variational equations along homothetic solutions are solvable. We obtain sufficient conditions for nonintegrability for these exceptional cases by focusing on some particular solutions that are different from homothetic solutions.

Using the variational method, Chenciner and Montgomery (2000 Ann. Math. 152 881-901) proved the existence of an eight-shaped orbit of the planar three-body problem with equal masses. Since then a number of solutions to the $N$-body problem have been discovered. On the other hand, symbolic dynamics is one of the most useful methods for understanding chaotic dynamics. The Sitnikov problem is a special case of the three-body problem. The system is known to be chaotic and was studied by using symbolic dynamics (J.Moser, Stable and random motions in dynamical systems, Princeton University Press, 1973).
In this paper, we study the limiting case of the Sitnikov problem. By using the variational method, we show the existence of various kinds of solutions in the planar Sitnikov problem. For a given symbolic sequence, we show the existence of orbits realizing it. We also prove the existence of periodic orbits.

A mathematical billiard consists of a planar region as a table and a ball moving on the table and reflecting from the boundary. By considering the motion as a discrete dynamical system, the billiard map is an area-preserving twist map. In this work, we show the result of nonexistence of invariant curves for two different billiard maps. The first result presents a sufficient condition for the nonexistence of invariant curves. In the second one, we prove the nonexistence of invariant curves near the boundary for Halpern’s billiard, which has a convergent billiard orbit.

The triple linkage of Thurston and Weeks exhibits Anosov behavior for certain parameter values, which can be shown by examining the Gauss curvature of the configuration space equipped with the metric induced by kinetic energy. In this paper, we consider a spatial linkage that can be viewed as a conversion of the triple linkage. We show that the configuration space asymptotically becomes a Riemannian submanifold of the four-dimensional torus $\mathbb{T}^4$ taking the limit of the parameters. Through verified numerical computation, we demonstrate that the asymptotic configuration space has negative curvature, and hence that for parameters close to the limit the linkage is Anosov by structural stability of an Anosov flow.