Twisted Homoclinic Orbits in Lorenz and Chen Systems: Rigorous Proofs Using Universal Normal Form

The properties common to the Lorenz and Chen attractors, as well as their fundamental differences, have been studied for many years in a vast number of works and remain a topic far from a rigorous and complete description. In this paper, we take a step toward to solving this problem by carrying out a rigorous study of the so-called universal normal form to which we have reduced the systems of both of these families. For this normal form, we prove the existence of infinite set of homoclinic orbits with different topological structures defined by the number of rotations around axis of symmetry. We show that these rotational topological features are inherited by the attractors of Chen-type systems and give rise to their twisted nature — the generic difference from attractors of Lorenz-type systems.