(In search of) The predictive axion
by
1/1-2 - Aula "C. Voci"
Dipartimento di Fisica e Astronomia - Edificio Marzolo
The cosmological history of an axion is most predictive and signal-rich when its associated symmetry is restored in the early universe, giving rise to a network of axion cosmic strings. Their evolution washes out initial data, most notably leading to a unique QCD axion mass compatible with dark matter. However, this scenario is often deemed in tension with QCD axion models that address the PQ quality problem, particularly those descending from gauge theory in extra dimensions and underpinning the “axiverse”. In this talk, I will argue that the latter are easily and generically reconciled from the model-building perspective (through the inclusion of localised charged fields or a 't Hooft-Polyakov mechanism) and discuss several aspects of phenomenology. Time permitting, I will highlight the need to explore more general QCD axion defects to properly test the predictive power of axion cosmology.