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...

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...

Considering jets, or functions, belonging to some strongly non-quasianalytic Carleman class on compact subsets of ${ℝ}^n$, we extend them to the whole space with a loss of Carleman regularity. This loss is related to geometric conditions refining Łojasiewicz’s “regular separation” or Whitney’s “property (P)”.

Si $f$ est un germe ${𝒞}^{\infty }$ de $({\mathbf{R}}^n,0)$, on dira que $f$ est une pseudo-immersion (on notera $f\in {\Psi }_{n,m}$) si tous les germes continus $g$ de $(\mathbf{R},0)$ dans $({\mathbf{R}}^m,0)$, tels que $f\circ g\in {𝒞}^{\infty }$ sont eux-mêmes ${𝒞}^{\infty }$. On détermine complètement ${\Psi }_{n,1}$, et on montre que ${\Psi }_{2,2}={\mathrm{Diff}}_2$. Par ailleurs, si $\mathbf{K}=\mathbf{R}$ ou $\mathbf{C}$ et si $g$ est une application de $\mathbf{K}$ dans $\mathbf{K}$ telle que $g^2$ et $g^3$ sont ${𝒞}^{\infty }$, alors $g$ est aussi ${𝒞}^{\infty }$. Si $\mathbf{K}=\mathbf{H}$ (corps des hamiloniens) alors cette implication n’est plus vraie.