Symmetric homoclinic tangles in reversible dynamical systems have positive topological entropy

Abstract

We consider reversible vector fields in ${\mathbb{R}}^{2n}$ such that the set of fixed points of the involutory reversing symmetry is $n$-dimensional. Let such system have a smooth one-parameter family of symmetric periodic orbits which is of saddle type in normal directions. We establish that topological entropy is positive when the stable and unstable manifolds of this family of periodic orbits have a strongly-transverse intersection.

27 pages, 6 figures