Effective field theory and non-Gaussianity from general inflationary states

TL;DR

This paper investigates how non-trivial initial quantum states during inflation influence observable non-Gaussian features, using an effective field theory approach to distinguish between different initial conditions in a model-independent manner.

Contribution

It develops a Green's function/path integral framework to incorporate initial state effects into inflationary fluctuations and examines their impact on the bispectrum and consistency relations.

Findings

Consistency relation is state-dependent and can be violated with certain initial states.

Initial states can preserve information beyond the minimal number of e-folds.

Physically consistent initial states may include non-Gaussianities without violating fundamental relations.

Abstract

We study the effects of non-trivial initial quantum states for inflationary fluctuations within the context of the effective field theory for inflation constructed by Cheung et al. which allows us to discriminate between different initial states in a model-independent way. We develop a Green's function/path integral based formulation that incorporates initial state effects and use it to address questions such as how state-dependent is the consistency relation for the bispectrum, how many e-folds beyond the minimum required to solve the cosmological fine tunings of the big bang are we allowed so that some information from the initial state survives until late times, among others. We find that the so-called consistency condition relating the local limit of the bispectrum and the slow-roll parameter is a state-dependent statement that can be avoided for physically consistent initial states either with or without initial non-Gaussianities.