Stochastic Inflation and Dimensional Reduction

TL;DR

This paper introduces a replica field-theoretic approach to stochastic inflation, revealing a dimensional reduction phenomenon that influences super-horizon scales and modifies the spectral index, with implications for non-Gaussianity.

Contribution

It presents a novel replica field-theoretic method to analyze stochastic inflation and uncovers a scale-dependent dimensional reduction effect impacting large-scale cosmological features.

Findings

Dimensional reduction dominates at large scales and grows exponentially with time.

The spectral index is modified on super-horizon scales due to this effect.

A direct relation between noise correlator and non-Gaussianity parameter f_NL is established.

Abstract

We present a replica field-theoretic approach to stochastic inflation in which a manifestation of dimensional reduction is found. The scale above which the latter dominates grows exponentially fast with time and thus affects largest super-horizon scales. We find inevitable modifications of the spectral index on those scales. An explicit relation between the noise correlator and the non-gaussianity parameter f_NL is found.