A worldsheet perspective on string inflation

Understand

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.