[HEX-HET] Computing the Uncomputable: String Theory, Axions, and Neural Networks

Speaker: Thomas Rhys Harvey, MIT

Title: “Computing the Uncomputable: String Theory, Axions, and Neural Networks”

Abstract:

Axions are ubiquitous in string theory, and large ensembles of compactifications have mapped out their masses and couplings to photons without ever solving for the metric of the extra dimensions. Their couplings to quarks and leptons are a different story. These require a realistic particle-physics sector, and they depend on mathematical objects that probably exist but have no closed form: the Ricci-flat metric on the Calabi–Yau, the Hermitian Yang–Mills gauge field, and the field profiles of the matter fields. In this talk, I will show how neural networks can solve for these numerically and use them to compute, for the first time, the leading axion–matter couplings in heterotic string compactifications with realistic particle spectra. The results show a characteristic hierarchy. The model-dependent axions couple to fermions at tree level, much like DFSZ axions. The model-independent axion, which we find is essentially always the QCD axion, has loop-suppressed couplings, like a KSVZ axion.