Finiteness properties of automorphism spaces of manifolds with finite fundamental group

Abstract

Given a closed smooth manifold $M$ of even dimension $2n\ge 6$ with finite fundamental group, we show that the classifying space $\mathrm{BDiff}(M)$ of the diffeomorphism group of $M$ is of finite type and has finitely generated homotopy groups in every degree. We also prove a variant of this result for manifolds with boundary and deduce that the space of smooth embeddings of a compact submanifold $N\subset M$ of arbitrary codimension into $M$ has finitely generated higher homotopy groups based at the inclusion, provided the fundamental group of the complement is finite. As an intermediate result, we show that the group of homotopy classes of simple homotopy self-equivalences of a finite CW complex with finite fundamental group is up to finite kernel commensurable to an arithmetic group.

arXiv comment35 pages, major revision (including new results on finiteness properties of groups of isotopy classes of diffeomorphisms, and on arithmeticity of groups of homotopy classes of simple homotopy equivalences), to appear in Mathematische Annalen