  A scalar potential coupled to other fields of large disparate masses will
exhibit power suppression of the quantum loop corrections from these massive
fields. Quintessence fields in the dark energy regime and inflaton fields
during inflation often have a very large background field value. Thus any other
field with its mass dependent on the quintessence/inflaton background field
value through a moderate coupling will become very massive during the dark
energy/inflation phase and its quantum corrections to the scalar effective
potential will be suppressed. This concept is developed in this paper using the
decoupling theorem. The problem then reduces to a quantitative question of the
size of suppression effects within the parameter space of coupling constants,
scalar field background value and renormalization scale. Some numerical
examples are presented both for inflation and quintessence, but the approach is
general and can be applied to any scalar field effective potential. The
consequences to dark energy of the decoupling effect developed here is that the
quintessence field need not just be an incredibly weakly interacting field,
often added as simply an add-on to generate dark energy and have no other
purpose. Instead, this quintessence field could play a central role in the
particle physics dynamics at early times and then simply decouple at late times
before the onset of the dark energy phase. For inflation a consequence is
coupling of the inflaton to other fields can be much larger in certain models,
without needing supersymmetry to control quantum corrections.
