A worldsheet perspective on string inflation

TL;DR

This paper explores how string theory constraints influence slow-roll inflation, linking cosmological parameters to worldsheet conformal field theory properties and emphasizing the non-perturbative nature of inflation in string theory.

Contribution

It provides a framework connecting slow-roll inflation parameters to worldsheet beta functions, highlighting the non-perturbative aspects of string inflation.

Findings

Inflation depends on macroscopic matter sector properties.

String inflation is inherently non-perturbative in the string coupling g_s.

Tree-level string theory is insufficient to describe inflation.

Abstract

We investigate the constraints of slow-roll inflation on the string worldsheet. A general gravity-matter set-up is used in which the worldsheet consists of an abstract CFT coupled to a 3+1 dimensional non-linear sigma model. The empirical slow-roll parameters are expressed in terms of the beta functions of operators in the matter/internal CFT and the beta function of the dilaton. The result confirms that inflation is only sensitive to macroscopic properties of the matter sector, and that in string theory inflation is a non-perturbative (in g_s) phenomenon and one must go beyond tree-level string theory.