Topical seminar: From minimal to general: the structure of axion solutions to the strong CP problem

por Dr. Mario Fernández Navarro (Universität Zürich)

lunes 9 nov. 2026 12:00 → 13:30 Europe/Madrid

1001-Primera-1-1-1 - Paterna. Seminario (Universe)

The QCD axion provides a compelling solution to the strong CP problem. In this talk I will discuss a minimal origin for the otherwise unspecified Peccei-Quinn symmetry of the QCD axion based on an extra-dimensional gauge theory, which nevertheless retains much of the simplicity and mass-coupling prediction of minimal QCD axion models. I will then consider more general scenarios involving additional PQ-breaking sources compatible with the strong CP solution, and/or multiple axion states originating from extra PQ symmetries. I will show that the photon-coupling phenomenology is qualitatively controlled by two structural properties: whether a linear combination of PQ symmetries broken only by QCD exists, and whether the anomaly coefficients are universal. This leads to a general sum rule governing the (multi-)axion system, helping to connect a potential experimental signature with the underlying axion potential and its UV completion. Finally, I will highlight the flavour deconstruction of QCD as an illustrative UV realisation of many qualitative multi-axion regimes