Each Lie algebra $ℱ$ of vector fields (e.g. those which are tangent to a foliation) of a smooth manifold $M$ définies, in a natural way, a spectral sequence $E_k\left(ℱ\right)$ which converges to the de Rham cohomology of $M$ in a finite number of steps. We prove e.g. that for all $k\ge 0$ there exists a foliated compact manifold with $E_k\left(ℱ\right)$ infinite dimensional.

We give several sufficients conditions for a 2-cycle of $B$ Diff$(S^1{)}_d$ (resp. $B$ Diff${}_K(\mathbf{R}{)}_d$) represented by a foliated $S^1$-(resp. $\mathbf{R}$-) bundle over a 2-torus to be homologous to zero. Such a 2-cycle is determined by two commuting diffeomorphisms $f$, $g$ of $S^1$ (resp. $\mathbf{R}$). If $f$, $g$ have fixed points, we construct decompositions: $f=\pi f_i$, $g=\pi g_i$, where the interiors of Supp$\left(f_i\right)\cup$ Supp$\left(g_i\right)$ are disjoint, and $f_i$ and $g_i$ belong either to $\{h_i^n;n\in \mathbf{Z}\}$ ($h_i\in$ Diff${}^{\infty }$) or to a one-parameter subgroup generated by a $C^1$-vectorfield ${\xi }_i$. Under some conditions on the norms...

In the present paper we determine for each parallelizable smooth compact manifold $M$ the second cohomology spaces of the Lie algebra ${𝒱}_M$ of smooth vector fields on $M$ with values in the module $\overline{\Omega }{}_M^p={\Omega }_M^p/d{\Omega }_M^{p-1}$. The case of $p=1$ is of particular interest since the gauge algebra of functions on $M$ with values in a finite-dimensional simple Lie algebra has the universal central extension with center ${\overline{\Omega }}_M^1$, generalizing affine Kac-Moody algebras. The second cohomology $H^2({𝒱}_M,{\overline{\Omega }}_M^1)$ classifies twists of the semidirect product of ${𝒱}_M$ with the...

The continuous cohomology theory of the Lie algebra $L\left(M\right)$ of complex analytic vector fields on an open Riemann surface $M$ is studied. We show that the cohomology group with coefficients in the $L\left(M\right)$-module of germs of complex analytic tensor fields on the product space $M^n$ decomposes into the global part derived from the homology of $M$ and the local part coming from the coefficients.

By choosing certain Birkhoff’s section to the geodesic flow of a negatively curved closed surface, E. Ghys showed that the unstable foliation of the geodesic flow has a transversely piecewise linear structure. We explicitly describe the holonomy homomorphism induced by this transversely piecewise linear structure and calculate its discrete Godbillon-Vey invariant.

Nous démontrons la finitude de la cohomologie de l’algèbre de Lie des champs de vecteurs formels à $2n+1$ variables, respectant la forme de contact universelle $w=d{x}_0+{\sum }_{i=1}^n{x}_{i}d{\bar{x}}_i$.