While there have been many investigations about the effect of particle
production at the end of inflation (i.e. preheating) or while observable
modes cross the horizon, there is a long period between these two events.
I will demonstrate the effects of a brief period of particle production
which occurs after the observable cosmological scales have exited the
Hubble radius. In multiple-field inflation this may lead to observable
signatures in the CMB and large scale structure, because the back reaction
of the particle production onto the inflaton(s) will depend on the
inflationary trajectory (and hence on the position in the universe). In
particular non-Gaussianity of the curvature perturbation places
interesting constraints on such a scenario.