Universality in Multifield Inflation from String Theory

TL;DR

This paper introduces a numerical method to analyze linear cosmological fluctuations in multi-field inflation models from string theory, revealing common features and observational tensions in these scenarios.

Contribution

It develops a new statistical approach to study multi-field inflation in string theory and applies it to six-field models, highlighting typical dynamics and observational challenges.

Findings

Slow-roll violations are common in models with over 60 e-folds.

Bending trajectories and many-field effects frequently occur.

Models with significant effects are often inconsistent with observational data.

Abstract

We develop a numerical statistical method to study linear cosmological fluctuations in inflationary scenarios with multiple fields, and apply it to an ensemble of six-field inflection point models in string theory. The latter are concrete microphysical realizations of quasi-single-field inflation, in which scalar masses are of order the Hubble parameter and an adiabatic limit is reached before the end of inflation. We find that slow-roll violations, bending trajectories and 'many-field' effects are commonplace in realizations yielding more than 60 e-folds of inflation, although models in which these effects are substantial are in tension with observational constraints on the tilt of the scalar power spectrum.