Effective Field Theories and Inflation

TL;DR

This paper examines how high-energy physics might influence inflationary predictions, showing that heavy physics can have observable effects on the CMB even when decoupling occurs, and emphasizes the importance of searching for deviations from standard inflation models.

Contribution

It demonstrates that effective field theories can incorporate heavy-physics effects on inflationary predictions, which may be observable in the CMB despite decoupling, contrasting with previous findings.

Findings

Heavy-physics can produce observable effects in the CMB.

Decoupling does not necessarily eliminate heavy-physics influence.

Searching for deviations from standard inflation predictions remains valuable.

Abstract

We investigate the possible influence of very-high-energy physics on inflationary predictions focussing on whether effective field theories can allow effects which are parametrically larger than order H^2/M^2, 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 H^2/M^2 << 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 hep-th/0210233, 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 hep-th/0210233, 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.