  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.
