Smooth perfectness through decomposition of diffeomorphisms into fiber preserving ones

Abstract

We show that on a closed smooth manifold $M$ equipped with $k$ fiber bundle structures whose vertical distributions span the tangent bundle, every smooth diffeomorphism $f$ of $M$ sufficiently close to the identity can be written as a product $f=f_1...f_k$, where $f_i$ preserves the $i^{\text{th}}$-fiber. The factors $f_i$ can be chosen smoothly in $f$. We apply this result to show that on a certain class of closed smooth manifolds every diffeomorphism sufficiently close to the identity can be written as product of commutators and the factors can be chosen smoothly. Furthermore we get concrete estimates on how many commutators are necessary.