On Inflation and de Sitter in Non-Geometric String Backgrounds

TL;DR

The paper investigates how nongeometric string backgrounds, analyzed through double field theory, can generate 4D potentials supporting Minkowski and de Sitter vacua and enable inflation via monodromies. By deriving an elliptic flux-based potential and examining its vacuum structure, the authors show that elliptic monodromies can enlarge moduli field ranges, potentially facilitating chaotic-inflation-like dynamics without extra uplifting ingredients. They construct a toy inflation model where the inflaton arises from a fibre modulus, yielding V(φ) with quadratic and quartic terms whose parameters depend on the fibre volume and fluxes; slow-roll requires small fluxes and sub-stringy fibre volumes, implying very large monodromy orders. The work highlights both the promise of nongeometric backgrounds for cosmology and the need for more realistic constructions and precise EFT control, suggesting avenues such as exploring higher-order, hyperbolic, and sporadic monodromies and more intricate compactifications.

Abstract

We study the problem of obtaining de Sitter and inflationary vacua from dimensional reduction of double field theory (DFT) on nongeometric string backgrounds. In this context, we consider a new class of effective potentials that admit Minkowski and de Sitter minima. We then construct a simple model of chaotic inflation arising from T-fold backgrounds and we discuss the possibility of trans-Planckian field range from nongeometric monodromies as well as the conditions required to get slow roll.

Figures (2)

• Figure 1: By introducing a parabolic monodromy, the field range of $\rho_R$ ($H$-flux) or $\tau_R$ ($f$-flux) is enlarged from $[-1/2,1/2)$ to $(-\infty,\infty)$.
• Figure 2: Fundamental domain for $SL(2,\mathbb{Z})/\mathbb{Z}_4$ (a) and for $SL(2,\mathbb{Z})/\mathbb{Z}_6$ (b).