Inflation , as proposed, leaves the universe cold and empty. The compensating theory of reheating or preheating then needed to operate after inflationary era. Such theories prefer three legs bosonic decays φ→χχ, which doesn't have any analogy with standard model processes as much as I know. How and on which foundation one could handle the properties of these decays, like decay rate, running of the coupling constant and so on. I just know that such interactions could appear in the Lagrangian by assuming g φ^2χ^2 term and spontaneous symmetry-breaking for the inflaton φ afterward. Of course, the Higg's decay into two photons or two W's have to be considered as close realistic counterparts, though they are gouge particles. I'll appreciate any comment as well as introducing linked references. Thanks.