"Deforming endomorphisms of abelian varieties and arithmetic applications" Abstract: Given an abelian variety A over a finite field F, we consider the problem of which endomorphisms of A extend to a deformation of A to an artinian ring with residue field F. The problem is motivated by recent work by the speaker and K. Lauter on constructing units in abelian extensions of CM fields by means of special values of modular functions. While I shall report briefly on this motivation and the application, due to time limitation I shall focus on the particular deformation problem.