On the Possibility of Large Axion Moduli Spaces

Abstract

We study the diameters of axion moduli spaces, focusing primarily on type IIB compactifications on Calabi-Yau three-folds. In this case, we derive a stringent bound on the diameter in the large volume region of parameter space for Calabi-Yaus with simplicial Kähler cone. This bound can be violated by Calabi-Yaus with non-simplicial Kähler cones, but additional contributions are introduced to the effective action which can restrict the field range accessible to the axions. We perform a statistical analysis of simulated moduli spaces, finding in all cases that these additional contributions restrict the diameter so that these moduli spaces are no more likely to yield successful inflation than those with simplicial Kähler cone or with far fewer axions. Further heuristic arguments for axions in other corners of the duality web suggest that the difficulty observed in hep-th/0303252 of finding an axion decay constant parametrically larger than $M_p$ applies not only to individual axions, but to the diagonals of axion moduli space as well. This observation is shown to follow from the weak gravity conjecture of hep-th/0601001, so it likely applies not only to axions in string theory, but also to axions in any consistent theory of quantum gravity.

26+11 pages, 9 figures, discussion of relationship to weak gravity conjecture added v2, references added v3, minor changes v4, matches publication version

References in corpus (8)

• On the Geometry of the String Landscape and the Swampland
• A Joint Analysis of BICEP2/Keck Array and Planck Data
• The String Landscape and the Swampland
• Fitting the Gamma-Ray Spectrum from Dark Matter with DMFIT: GLAST and the Galactic Center Region
• Axion Inflation in Type II String Theory
• Volume Modulus Inflation and the Gravitino Mass Problem
• Axion Inflation and Gravity Waves in String Theory
• Heavy Tails in Calabi-Yau Moduli Spaces

Cited by in corpus (14)

• Physics potential of the International Axion Observatory (IAXO)
• The Weak Gravity Conjecture in three dimensions
• The Weak Gravity Conjecture and Effective Field Theory
• Constraining Neutrino Masses, the Cosmological Constant and BSM Physics from the Weak Gravity Conjecture
• Can Gravitational Instantons Really Constrain Axion Inflation?
• The Convex Hull Swampland Distance Conjecture and Bounds on Non-geodesics
• An Axion-induced SM/MSSM Higgs Landscape and the Weak Gravity Conjecture
• Large Field Ranges from Aligned and Misaligned Winding
• Systematics of Aligned Axions
• Are tiny gauge couplings out of the Swampland?
• Inflation Expels Runaways
• Fencing in the Swampland: Quantum Gravity Constraints on Large Field Inflation
• Quantum coherence of photons at cosmological distances
• Covariant Quantum Gravitational Corrections to Scalar and Tensor Field Models