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The Challenge of Realizing F-term Axion Monodromy Inflation in String Theory

Ralph Blumenhagen, Daniela Herschmann, Erik Plauschinn

TL;DR

The paper systematically assesses the viability of realizing single-field F-term axion monodromy inflation in type IIB flux compactifications. It shows a no-go for inflaton candidates that involve the universal axion $C_0$ within the flux-induced no-scale potential, while demonstrating that a purely complex-structure axion inflaton is possible only under specific rank conditions on flux-induced couplings and prepotential data, supported by explicit examples. A general hierarchical stabilization framework is developed to separate heavy moduli from the inflaton, yielding a tunable inflaton mass relative to heavy moduli under controlled approximations, though backreaction and large-field control remain challenging. Collectively, the results constrain viable string-realizations of F-term axion monodromy and pave the way for constructing explicit, fully stabilized models that maintain a light axionic inflaton beyond the universal axion sector.

Abstract

A systematic analysis of possibilities for realizing single-field F-term axion monodromy inflation via the flux-induced superpotential in type IIB string theory is performed. In this well-defined setting the conditions arising from moduli stabilization are taken into account, where we focus on the complex-structure moduli but ignore the Kaehler moduli sector. Our analysis leads to a no-go theorem, if the inflaton involves the universal axion. We furthermore construct an explicit example of F-term axion monodromy inflation, in which a single axion-like field is hierarchically lighter than all remaining complex-structure moduli.

The Challenge of Realizing F-term Axion Monodromy Inflation in String Theory

TL;DR

The paper systematically assesses the viability of realizing single-field F-term axion monodromy inflation in type IIB flux compactifications. It shows a no-go for inflaton candidates that involve the universal axion within the flux-induced no-scale potential, while demonstrating that a purely complex-structure axion inflaton is possible only under specific rank conditions on flux-induced couplings and prepotential data, supported by explicit examples. A general hierarchical stabilization framework is developed to separate heavy moduli from the inflaton, yielding a tunable inflaton mass relative to heavy moduli under controlled approximations, though backreaction and large-field control remain challenging. Collectively, the results constrain viable string-realizations of F-term axion monodromy and pave the way for constructing explicit, fully stabilized models that maintain a light axionic inflaton beyond the universal axion sector.

Abstract

A systematic analysis of possibilities for realizing single-field F-term axion monodromy inflation via the flux-induced superpotential in type IIB string theory is performed. In this well-defined setting the conditions arising from moduli stabilization are taken into account, where we focus on the complex-structure moduli but ignore the Kaehler moduli sector. Our analysis leads to a no-go theorem, if the inflaton involves the universal axion. We furthermore construct an explicit example of F-term axion monodromy inflation, in which a single axion-like field is hierarchically lighter than all remaining complex-structure moduli.

Paper Structure

This paper contains 20 sections, 107 equations, 1 figure.

Table of Contents

  1. Introduction
  2. String-theoretic challenges of axion inflation
  3. Moduli stabilization by fluxes
  4. Flux-induced potential
  5. Massless axions
  6. Examples with parametrically light moduli
  7. The isotropic torus
  8. The non-isotropic torus
  9. A model on ${\rm IP}_{1,1,2,2,2}[8]$
  10. General structure of light axions
  11. General procedure of hierarchical moduli stabilization
  12. No-go theorems
  13. Case A2
  14. Summary
  15. A concrete example with the desired properties
  16. ...and 5 more sections

Figures (1)

  • Figure 1: Contour plot of the vanishing locus of $f(v_2,v_3)=0$ (in blue) and $g(v_2,v_3)=0$ (in red), showing a common zero at $(v_2,v_3) = (-1.104, 1.155)$.