Two-point correlators revisited: Fast and slow scales in multifield models of inflation

TL;DR

This paper introduces a new method using Cholesky decomposition to efficiently compute primordial spectra in multifield inflation models by separating fast and slow evolving components, avoiding the slow-roll approximation.

Contribution

It presents a novel approach that rewrites equations of motion in terms of slowly varying quantities, improving accuracy and computational efficiency in spectrum calculations.

Findings

Method effectively separates fast and slow modes.

Accurate spectrum calculation without slow-roll approximation.

Enhanced computational performance for multifield models.

Abstract

We study the structure of two-point correlators of the inflationary field fluctuations in order to improve the accuracy and efficiency of the existing methods to calculate primordial spectra. We present a description motivated by the separation of the fast and slow evolving components of the spectrum which is based on Cholesky decomposition of the field correlator matrix. Our purpose is to rewrite all the relevant equations of motion in terms of slowly varying quantities. This is important in order to consider the contribution from high-frequency modes to the spectrum without affecting computational performance. The slow-roll approximation is not required to reproduce the main distinctive features in the power spectrum for each specific model of inflation.