Quantum Contributions to Cosmological Correlations

TL;DR

This paper reviews and extends the in-in formalism to compute higher-order cosmological correlations, including loop graphs, revealing their dependence on the inflaton potential near horizon exit.

Contribution

It introduces the calculation of loop graphs in the in-in formalism for cosmological correlations, expanding beyond previous tree-level analyses.

Findings

Loop contributions depend mainly on the inflaton potential near horizon exit.

A sample one-loop calculation demonstrates the formalism.

Loop graphs can influence Gaussian and non-Gaussian correlations.

Abstract

The ``in-in'' formalism is reviewed and extended, and applied to the calculation of higher-order Gaussian and non-Gaussian correlations in cosmology. Previous calculations of these correlations amounted to the evaluation of tree graphs in the in-in formalism; here we also consider loop graphs. It turns out that for some though not all theories, the contributions of loop graphs as well as tree graphs depend only on the behavior of the inflaton potential near the time of horizon exit. A sample one-loop calculation is presented.