Singularities of Vector Fields on the Plane With Pointed Direction.
Smooth linearization of germs of -actions and holomorphic vector fields
The paper contains a generic condition permitting the linearization in class , , of germs of singular infinitesimal -actions on and of singular holomorphic...
Some properly critical subsets of Euclidean spaces.
Some quantitative results in singularity theory
The classical singularity theory deals with singularities of various mathematical objects: curves and surfaces, mappings, solutions of differential equations, etc. In particular, singularity theory treats the tasks of recognition, description and classification of singularities in each of these cases. In many applications of singularity theory it is important to sharpen its basic results, making them "quantitative", i.e. providing explicit and effectively computable estimates for all the important...
Some stability questions concerning caustics for different propagation laws.
Stability modulo singular sets
A new concept of stability, closely related to that of structural stability, is introduced and applied to the study of C¹ endomorphisms with singularities. A map that is stable in this sense is conjugate to each perturbation that is equivalent to it in a geometric sense. It is shown that this kind of stability implies Axiom A and Ω-stability, and that every critical point is wandering. A partial converse is also shown, providing new examples of C³ structurally stable maps.
Stable mappings of 3-manifolds into the plane
Stokes' phenomenon; smoothing a victorian discontinuity
Stratifications of polynomial spaces
In the paper we construct some stratifications of the space of monic polynomials in real and complex cases. These stratifications depend on properties of roots of the polynomials on some given semialgebraic subset of R or C. We prove differential triviality of these stratifications. In the real case the proof is based on properties of the action of the group of interval exchange transformations on the set of all monic polynomials of some given degree. Finally we compare stratifications corresponding...
Structurally stable perturbations of polynomials in the Riemann sphere
Sufficiency of Jets via Stratification Theory.
Sufficient decrease principle on Riemannian manifolds.
Sur le modèle historique de Thom-Pomian
Sur le théorème des fonctions composées différentiables
Soit un morphisme propre relativement algébrique entre espaces semi-analytiques. On montre que si désigne l’anneau des fonctions de classe sur , l’image par de est fermée dans muni de sa topologie naturelle d’espace de Frechet ; ceci généralise un résultat précédent de J.-C. Tougeron (lui-même généralisant un résultat de Glaeser) qui traite du cas semi-algébrique. La méthode est tout à fait analogue et utilise des propriétés algébriques de l’anneau des fonctions Nash-analytiques introduit...
Sur les propriétés topologiques des projections lagrangiennes en géométrie symplectique des caustiques.
La caustique d?un point sur une variété riemannienne est l?ensemble des points d?intersection des géodésiques infiniment voisins partant de ce point. Jacobi a remarqué, en utilisant un raisonnement topologique, que la caustique d?un point sur une surface convexe fermée doit avoir des points de rebroussement. Il a aussi annoncé (sans démonstration) que le nombre de ces points est quatre pour les caustiques sur les surfaces d?ellipsoïdes (Jacobi, 1964). Dans cette note j?essaie d?inclure les théorèmes...
Sur les singularités des formes différentielles
On étudie, sur le modèle de la théorie des singularités d’applications différentiables, les singularités des formes différentielles extérieures sur une variété différentiable. Les invariants fondamentaux utilisés sont le rang et la classe (au sens de E. Cartan) d’une forme différentielle. On étudie leur comportement générique à l’aide des théorèmes de transversalité. Par exemple, l’ensemble des points d’une variété de dimension où la classe d’une forme de Pfaff est égale à est génériquement...
Survey of recent results on singularities of equivariant maps
Symmetric caustics and Curie's principle
Physical systems producing caustics may possess symmetries. In that case the relation between the symmetry of the system, considered as a whole, and the symmetry of the caustic follow a very general symmetry principle, the Curie principle. We give various examples of application of the Curie principle to caustics produced by the deflection of light in liquid crystals: the so called squint effect, the visualization of a new type of roll structure, etc. We show also that the Curie principle applies...
Symmetry Properties of Singularities of C°°-Functions.
Symplectic classification of parametric complex plane curves
Based on the discovery that the δ-invariant is the symplectic codimension of a parametric plane curve singularity, we classify the simple and uni-modal singularities of parametric plane curves under symplectic equivalence. A new symplectic deformation theory of curve singularities is established, and the corresponding cyclic symplectic moduli spaces are reconstructed as canonical ambient spaces for the diffeomorphism moduli spaces which are no longer Hausdorff spaces.