Effective field theories and inflation

We investigate the possible influence of very-high-energy physics on inflationary predictions, focusing on whether effective field theories can allow effects which are parametrically larger than order H²/M², where M is the scale of heavy physics and H is the Hubble scale at horizon exit. By investigating supersymmetric hybrid inflation models, we show that decoupling does not preclude heavy physics having effects for the CMB with observable size even if H²/M² ≪ O(1%), although their presence can only be inferred from observations given some a priori assumptions about the inflationary mechanism. Our analysis differs from the results of our earlier work, in which other kinds of heavy-physics effects were found which could alter inflationary predictions for CMB fluctuations, inasmuch as the heavy-physics can be integrated out here to produce an effective field theory description of low-energy physics. We argue, as in our earlier work, that the potential presence of heavy-physics effects in the CMB does not alter the predictions of inflation for generic models, but does make the search for deviations from standard predictions worthwhile. © 2003 IOP Publishing Ltd.