Title: Precision Physics of the QCD axion and other new light particles
Abstract: I will discuss the properties, and constraints on, new light particles which appear in many extensions of the Standard Model. An especially well motivated example is the QCD axion, and I will show how its mass and couplings can be extracted at high precision by combining chiral perturbation theory and recent lattice results. I will also discuss the unreliability of conventional instanton approaches at finite temperature and study the impact on axion dark matter and cosmology. More generally, strong constraints on the couplings of new light particles to the Standard Model arise from their production in the hot cores of stars, and the effect of this on stellar cooling. The large electron density in stellar cores giving large thermal effects. I will show how these effects can parametrically change the production rates compared to a 'tree level' calculation.