Flavour-violating signatures of non-universal axion models

The axion provides a well-motivated extension of the Standard Model (SM) addressing the strong CP problem and yielding a dark matter candidate, with implications across particle physics, astrophysics and cosmology. It has been recently pointed out that non-universal axion models (in which the axion does not couple in the same way to each SM fermion generation) allow to suppress the axion coupling to nucleons and relax in turn astrophysical axion bounds. A remarkable consequence of non-universal axion models are flavour-violating axion couplings, which can be tested in low-energy flavour experiments. The aim of the thesis is to study the interplay between different sources of flavour violation, involving both the axion and the heavy radial modes which are unavoidably present in ultraviolet complete non-universal axion models.