The Zeta-Zeta Correlator Is Time Dependent

TL;DR

This paper discusses the time dependence of the zeta-zeta correlator during inflation, showing that certain quantum effects can introduce secular growth without threatening super-horizon correlations.

Contribution

It demonstrates that loop corrections to the zeta-zeta correlator can exhibit secular time dependence due to inflationary particle production, challenging previous claims.

Findings

Examples of time dependence from quantum gravity and scalar models.

Secular growth arises from inflationary particle production.

Time dependence does not threaten super-horizon correlations.

Abstract

We comment on the recent arguments by Senatore and Zaldarriaga that loop corrections to the zeta-zeta correlator cannot grow with time after first horizon crossing. We first emphasize the need to search for such secular dependence in corrections whose in-out matrix elements are infrared singular on an infinite spatial manifold. Then we give examples of such time dependence from pure quantum gravity and from scalar potential models. Finally, we point out that this time dependence arises from inflationary particle production and is therefore unlikely to endanger the preservation of super-horizon correlations as a record of inflation.