  An effective description of an initial state is a method for representing the
signatures of new physics in the short-distance structure of a quantum state.
The expectation value of the energy-momentum tensor for a field in such a state
contains new divergences that arise when summing over this new structure. These
divergences occur only at the initial time at which the state is defined and
therefore can be cancelled by including a set of purely geometric counterterms
that also are confined to this initial surface. We describe this gravitational
renormalization of the divergences in the energy-momentum tensor for a free
scalar field in an isotropically expanding inflationary background. We also
show that the back-reaction from these new short-distance features of the state
is small when compared with the leading vacuum energy contained in the field.
