Speaker
Description
Axion-like particles are currently among the most popular dark matter candidates. Considerable theoretical efforts have gone into expanding the parameter window of the quantum chromodynamics (QCD) axion beyond the narrow QCD band. The $Z_\mathcal{N}$ QCD axion model is the only such model which reduces the QCD axion mass naturally. The $Z_\mathcal{N}$ model invokes a discrete $Z_\mathcal{N}$ symmetry through which the axion field is coupled to $\mathcal{N}$ QCD dark sectors, yielding an effective potential with $\mathcal{N}$ degenerate minima. Lattice simulations provide a robust means for gauging the viability of analytical and semi-analytical approximations, and for generating accurate predictions when they are insufficient. Having conducted the first lattice simulations of $Z_\mathcal{N}$ scenarios, we find their phenomenology to be significantly influenced by nonlinear phenomena such as parametric resonance and back-reaction. From these simulations, we present dark matter abundances as well as insights into whether or not $Z_\mathcal{N}$ axions can actually solve the strong CP problem.
