  An oscillating inflaton field induces small amplitude oscillations of the
Hubble parameter at the end of inflation. These Hubble parameter induced
oscillations, in turn, trigger parametric particle production of all light
fields, even if they are not directly coupled to the inflaton. We here study
the induced particle production for a light scalar field (e.g. the Standard
Model Higgs field) after inflation as a consequence of this effect. Our
analysis yields a model-independent lower bound on the efficiency of energy
transfer from the inflaton condensate to particle excitations.
