We use the theory of partially hyperbolic systems [HPS] in order to find singularities of index $1$ for vector fields with isolated zeroes in a $3$-ball. Indeed, we prove that such zeroes exists provided the maximal invariant set in the ball is partially hyperbolic, with volume expanding central subbundle, and the strong stable manifolds of the singularities are unknotted in the ball.

Let $\Sigma$ be a closed surface, $G$ a compact Lie group, with Lie algebra $g$, and $\xi :P\to \Sigma$ a principal $G$-bundle. In earlier work we have shown that the moduli space $N\left(\xi \right)$ of central Yang-Mills connections, with reference to appropriate additional data, is stratified by smooth symplectic manifolds and that the holonomy yields a homeomorphism from $N\left(\xi \right)$ onto a certain representation space ${\mathrm{Rep}}_{\xi }(\Gamma ,G)$, in fact a diffeomorphism, with reference to suitable smooth structures $C^{\infty }\left(N\right(\xi \left)\right)$ and $C^{\infty }\left({\mathrm{Rep}}_{\xi }(\Gamma ,G)\right)$, where $\Gamma$ denotes the universal central extension of...

Using the notion of the maximal polar quotient we characterize the critical values at infinity of polynomials in two complex variables. As an application we give a necessary and sufficient condition for a family of affine plane curves to be equisingular at infinity.

We generalize the Malgrange preparation theorem to matrix valued functions $F(t,x)\in C^{\infty }(\mathbf{R}\times {\mathbf{R}}^n)$ satisfying the condition that $t\mapsto \det F(t,0)$ vanishes to finite order at $t=0$. Then we can factor $F(t,x)=C(t,x)P(t,x)$ near (0,0), where $C(t,x)\in C^{\infty }$ is inversible and $P(t,x)$ is polynomial function of $t$ depending $C^{\infty }$ on $x$. The preparation is (essentially) unique, up to functions vanishing to infinite order at $x=0$, if we impose some additional conditions on $P(t,x)$. We also have a generalization of the division theorem, and analytic versions generalizing the Weierstrass preparation...

Singular projections of generic 2-dim surfaces in ℝ³ with singular boundary to 2-space are studied. The case of projections of surfaces with nonsingular boundary has been treated by Bruce and Giblin. The aim of this paper is to generalise these results to the simplest singular case where the boundary of the surface consists of two transversally intersecting lines. Local models for germs of generic singular projections of corank ≤ 1 and codimension ≤ 3 are given. We also present geometrical realisations...

We discuss some approaches to the topological study of real quadratic mappings. Two effective methods of computing the Euler characteristics of fibers are presented which enable one to obtain comprehensive results for quadratic mappings with two-dimensional fibers. As an illustration we obtain a complete topological classification of configuration spaces of planar pentagons.

A classification of simple equivalence classes of function germs with respect to new relations is given. The equivalence relation is similar but weaker than the right action of diffeomorphisms which preserve the boundary. It is used in classifying Lagrange projections with boundary. The simple classes of function germs with respect to the equivalence similar to fibration preserving action are also discussed.

Nous considérons les groupes de cobordisme (définis par Arnold) d’immersions lagrangiennes exactes de variétés compactes dans ${\mathbf{R}}^{2n}$. Grâce au théorème de Gromov-Lees, leur calcul est celui des groupes d’homotopie de spectres de Thom construits sur les espaces $U/O$ (cas non-orienté, le calcul est alors dû à Smith et Stong) et $U/SO$ (cas orienté, groupes dont nous calculons la “partie paire”, et sur la “partie impaire” desquels nous donnons des informations). Nous calculons aussi les images de ces groupes dans...

A stable deformation $f^t$ of a real map-germ $f:ℝⁿ,0\to {ℝ}^p,0$ is said to be an M-deformation if all isolated stable (local and multi-local) singularities of its complexification $f_{ℂ}^t$ are real. A related notion is that of a good real perturbation $f^t$ of f (studied e.g. by Mond and his coworkers) for which the homology of the image (for n < p) or discriminant (for n ≥ p) of $f^t$ coincides with that of $f_C^t$. The class of map germs having an M-deformation is, in some sense, much larger than the one having a good real perturbation....