On periodic solutions inside isolating chains
The author studies harmonics to nonautonomous ordinary differential equations. He develops a geometric technique allowing him to verify periodic orbits inside the union of continuous isolating segments (resembling isolating blocks). The main result allows him to compute the Lefschetz number of certain homomorphisms determined by these segments as a fixed-point index of the associated Poincaré maps. As a nontrivial application, some illustrating examples are given.
scientific article; zbMATH DE number 1538229