A note on homotopy and pseudoisotopy of diffeomorphisms of $4$-manifolds

Abstract

This note serves to record examples of diffeomorphisms of closed smooth $4$-manifolds $X$ that are homotopic but not pseudoisotopic to the identity, and to explain why there are no such examples when $X$ is orientable and its fundamental group is a free group.

arXiv comment5 pages, to appear in Comptes Rendus Mathématique