F-theory Axiverse

TL;DR

This paper investigates the properties of thousands of axions in F-theory compactifications, revealing universal couplings and mass patterns, and assessing their phenomenological viability against experimental constraints.

Contribution

It provides the first comprehensive analysis of axion couplings and masses in large ensembles of F-theory models with up to 181,200 axions, highlighting universal features and phenomenological tensions.

Findings

Axion-photon couplings increase with h^{1,1}

Models with h^{1,1} > 10,000 conflict with helioscope constraints

Models with h^{1,1} > 5,000 are in tension with X-ray observations

Abstract

We compute the couplings of Ramond-Ramond four-form axions in three ensembles of F-theory compactifications, with up to 181,200 axions. We work in the stretched K\"ahler cone, where $\alpha'$ corrections are plausibly controlled, and we use couplings to certain non-Abelian sectors as a proxy for couplings to photons. The axion masses, decay constants, and couplings to gauge sectors show striking universality across the ensembles. In particular, the axion-photon couplings grow with $h^{1,1}$, and models in our ensemble with $h^{1,1} \gtrsim$ 10,000 axions are in tension with helioscope constraints. Moreover, under mild assumptions about charged matter beyond the Standard Model, theories with $h^{1,1} \gtrsim$ 5,000 are in tension with Chandra measurements of X-ray spectra. This work is a first step toward understanding the phenomenology of quantum gravity theories with thousands of axions.