Decoupling Survives Inflation: A Critical Look at Effective Field Theory Violations During Inflation

摘要

We investigate the validity of effective field theory methods and thedecoupling of heavy fields during inflation. Considering models of inflation inwhich the inflaton is coupled to a heavy (super-Hubble) degree of freedominitially in its vacuum state, we find that violations of decoupling are absentunless there is a breakdown of the slow-roll conditions. Next we allow for atemporary departure from inflation resulting in a period of non-adiabaticityduring which effective field theory methods are known to fail. We find that thelocality of the event and energy conservation lead to a tight bound on the sizeof the effects of the heavy field. We discuss the implications for the powerspectrum and non-gaussianity, and comment on the connection with recent studiesof the dynamics of multi-field inflation models. Our results further motivatethe use of effective field theory methods to characterize cosmic inflation, andfocus the question of observability of additional degrees of freedom duringinflation to near the Hubble scale or below - as anticipated from the Wilsoniannotions of decoupling and naturalness.