Towards natural inflation from weakly coupled heterotic string theory

TL;DR

The paper addresses realizing natural inflation within weakly coupled heterotic string theory by using a Swiss-Cheese Calabi-Yau with multiple $U(1)$ fluxes to absorb most axions and leave a single Kähler axion as the inflaton. The trans-Planckian axion decay constant is achieved through one-loop corrections to the hidden gauge-kinetic function, while dilaton and Kähler moduli are stabilized so that heavy fields decouple during inflation. Two concrete models (Model 1 and Model 2) demonstrate how moduli stabilization and a natural-inflation potential $V_{ m eff} \simeq \Lambda^4 (1-\cos(\beta \hat{Y}))$ arise, yielding observables compatible with Planck/WMAP and BICEP2 data (with tunable $r$). The results illustrate a viable mechanism for large-field inflation in heterotic string theory and highlight the role of flux-induced FI terms, gaugino condensation, and worldsheet instantons in moduli stabilization and inflaton dynamics.

Abstract

We propose the natural inflation from the heterotic string theory on "Swiss-Cheese" Calabi-Yau manifold with multiple $U(1)$ magnetic fluxes. Such multiple $U(1)$ magnetic fluxes stabilize the same number of the linear combination of the universal axion and Kähler axions and one of the Kähler axions is identified as the inflaton. This axion decay constant can be determined by the size of one-loop corrections to the gauge kinetic function of the hidden gauge groups, which leads effectively to the trans-Planckian axion decay constant consistent with the WMAP, Planck and/or BICEP2 data. During the inflation, the real parts of the moduli are also stabilized by employing the nature of the "Swiss-Cheese" Calabi-Yau manifold.