Axion dark matter and the Lattice

Understand

First I will review the QCD theta problem and the Peccei-Quinn solution, with its new particle, the axion.

• I will review the possibility of the axion as dark matter.
• If PQ symmetry was restored at some point in the hot early Universe, it should be possible to make a definite prediction for the axion mass if it constitutes the Dark Matter.
• I will describe progress on one issue needed to make this prediction -- the dynamics of axionic string-wall networks and how they produce axions.