  In this paper we calculate the effect of the inclusion of exotic smooth
structures on typical observables in Euclidean quantum gravity. We do this in
the semiclassical regime for several gravitational free-field actions and find
that the results are similar, independent of the particular action that is
chosen. These are the first results of their kind in dimension four, which we
extend to include one-loop contributions as well. We find these topological
features can have physically significant results without the need for
additional exotic physics.
