We study the simultaneous linearizability of $d$–actions (and the corresponding $d$-dimensional Lie algebras) defined by commuting singular vector fields in ${ℂ}^n$ fixing the origin with nontrivial Jordan blocks in the linear parts. We prove the analytic convergence of the formal linearizing transformations under a certain invariant geometric condition for the spectrum of $d$ vector fields generating a Lie algebra. If the condition fails and if we consider the situation where small denominators occur, then...

We study germs of smooth vector fields in a neighborhood of a fixed point having an hyperbolic linear part at this point. It is well known that the “small divisors” are invisible either for the smooth linearization or normal form problem. We prove that this is completely different in the smooth Gevrey category. We prove that a germ of smooth $\alpha$-Gevrey vector field with an hyperbolic linear part admits a smooth $\beta$-Gevrey transformation to a smooth $\beta$-Gevrey normal form. The Gevrey order $\beta$ depends on...

We establish a polynomial normal form for a vector field having a limit cycle of multiplicity 2. The smooth classification problem for such fields is closely related to the problem of classification of germs $\Delta :({ℝ}^1,0)\to ({ℝ}^1,0)$, $\Delta \left(x\right)=x+c{x}^2+\cdots$, solved by F. Takens in 1973. Such germs appear as the germs of Poincaré return maps for semistable cycles, and a smooth conjugacy between any two such germs may be extended to a smooth orbital equivalence between the original fields.If one deals with smooth conjugacy of flows rather than...

Nous considérons les champs de vecteurs analytiques de $({ℂ}^n,0)$ de partie linéaire diagonale non nulle et dont les valeurs propres ${\lambda }_i\in ℂ$ vérifient des relations de résonances toutes engendrées par une seule relation $(r,\lambda )=0$ pour un certain vecteur $r\in {\mathbb{N}}^n$ non nul. Nous montrons que, dans un système de coordonnées locales holomorphes au voisinages de $0\in {ℂ}^n$, de tels champs de vecteurs se “mettent" sous une forme normale partielle, tout en exhibant des variétés invariantes, si l’on fait une hypothèse de petits diviseurs diophantiens....