Computing observables in curved multifield models of inflation - A guide (with code) to the transport method

TL;DR

This paper presents a practical guide and Mathematica code for applying the transport method to compute inflationary observables in complex multifield models with curved field space, including non-slow-roll and turning trajectories.

Contribution

It introduces a comprehensive, efficient approach for calculating inflationary observables in multifield models with curved field space, extending previous methods to more general scenarios.

Findings

The transport method is effective for models with curved field-space metrics.

The approach handles violations of slow-roll and turns in field space.

The accompanying code facilitates exploration of diverse inflationary models.

Abstract

We describe how to apply the transport method to compute inflationary observables in a broad range of multiple-field models. The method is efficient and encompasses scenarios with curved field-space metrics, violations of slow-roll conditions and turns of the trajectory in field space. It can be used for an arbitrary mass spectrum, including massive modes and models with quasi-single-field dynamics. In this note we focus on practical issues. It is accompanied by a Mathematica code which can be used to explore suitable models, or as a basis for further development.