The Evolution of Non-adiabatic Pressure Perturbations during Multi-field Inflation

TL;DR

This paper reviews non-adiabatic pressure perturbations in multi-field inflation and presents recent calculations of isocurvature spectra, highlighting their potential observational impacts on cosmic microwave background polarization.

Contribution

It provides a brief overview of non-adiabatic pressure perturbations and introduces new calculations of isocurvature spectra for two-field inflation models.

Findings

Isocurvature perturbations vary across models

Spectrum calculations inform observational signatures

Non-adiabatic effects influence curvature perturbations

Abstract

Non-adiabatic pressure perturbations naturally occur in models of inflation consisting of more than one scalar field. The amount of non-adiabatic pressure present at the end of inflation can have observational consequences through changes in the curvature perturbation, the generation of vorticity and subsequently the sourcing of B-mode polarisation. In this work, based on a presentation at the 13th Marcel Grossmann Meeting, we give a very brief overview of non-adiabatic pressure perturbations in multi-field inflationary models and describe our recent calculation of the spectrum of isocurvature perturbations generated at the end of inflation for different models which have two scalar fields.