Let , be an -th order differential operator, be its adjoint and be positive functions. It is proved that the self-adjoint equation is nonoscillatory at if and only if the equation is nonoscillatory at . Using this result a new necessary condition for property BD of the self-adjoint differential operators with middle terms is obtained.
An abstract theory on general synchronization of a system of several oscillators coupled by a medium is given. By generalized synchronization we mean the existence of an invariant manifold that allows a reduction in dimension. The case of a concrete system modeling the dynamics of a chemical solution on two containers connected to a third container is studied from the basics to arbitrary perturbations. Conditions under which synchronization occurs are given. Our theoretical results are complemented...
In this paper we deal with reversible vector fields on a 2-dimensional manifold having a codimension one submanifold as its symmetry axis. We classify generically the one parameter families of such vector fields. As a matter of fact, aspects of structural stability and codimension one bifurcation are analysed.
We study the generic invariant probability measures for the geodesic flow on connected complete nonpositively curved manifolds. Under a mild technical assumption, we prove that ergodicity is a generic property in the set of probability measures defined on the unit tangent bundle of the manifold and supported by trajectories not bounding a flat strip. This is done by showing that Dirac measures on periodic orbits are dense in that set.In the case of a compact surface, we get the following sharp result:...
Cascade second order ODEs on manifolds are defined. These objects are locally represented by coupled second order ODEs such that any solution of one of them can represent an external force for the other one. A generic saddle-node bifurcation theorem for 1-parameter families of cascade second order ODEs is proved.
We compute cohomology spaces of Lie algebras that describe differential invariants of third order ordinary differential equations. We prove that the algebra of all differential invariants is generated by 2 tensorial invariants of order 2, one invariant of order 3 and one invariant of order 4. The main computational tool is a Serre-Hochschild spectral sequence and the representation theory of semisimple Lie algebras. We compute differential invariants up to degree 2 as application.
Pour tout triplet d’entiers tels que , se pose la question d’étudier les germes de difféomorphismes ou de champs de vecteurs sur , de classe , -déterminés en classe , c’est-à-dire respectivement conjugués ou équivalents en classe , à tout germe ayant la même classe et le même -jet. Cette question est abordée ici, avec quelque généralité en dimension 2 et pour les germes de champs de vecteurs de codimension 2, en dimension 3 et 4. Une conséquence de cette dernière étude est l’existence...