Advances in Inflation in String Theory
Daniel Baumann, Liam McAllister
TL;DR
The paper analyzes how inflation can be realized within string theory and why Planck-scale physics critically shapes inflaton dynamics. It develops an EFT perspective, addresses the eta problem and radiative instabilities, and connects these issues to explicit string compactifications that yield the 4D inflaton action. A detailed case study of warped D-brane inflation illustrates a concrete small-field realization and demonstrates how UV completion constrains inflationary predictions. The work shows that robust connections between cosmological data and string theory require controlling high-energy corrections via specific compactifications and symmetries, with implications for tensor modes and future observational tests.
Abstract
We provide a pedagogical overview of inflation in string theory. Our theme is the sensitivity of inflation to Planck-scale physics, which we argue provides both the primary motivation and the central theoretical challenge for the subject. We illustrate these issues through two case studies of inflationary scenarios in string theory: warped D-brane inflation and axion monodromy inflation. Finally, we indicate how future observations can test scenarios of inflation in string theory.