Quotients of functors of Artin rings

Abstract

In infinitesimal deformation theory, a classical criterion due to Schlessinger gives an intrinsic characterisation of functors that are pro-representable, and more generally, of the ones that have a hull. Our result is that in this setting the question of characterising group quotients can also be answered. In other words, for functors of Artin rings that have a hull, those that are quotients of pro-representable ones by a constant group action can be described intrinsically.