Covariant Isotropy of Grothendieck Toposes

Abstract

We provide an explicit characterization of the covariant isotropy group of any Grothendieck topos, i.e. the group of (extended) inner automorphisms of any sheaf over a small site. As a consequence, we obtain an explicit characterization of the centre of a Grothendieck topos, i.e. the automorphism group of its identity functor.

21 pages plus 6 page appendix