  The Strong CP Problem can be resolved by introducing an additional global
symmetry known as Peccei-Quinn symmetry. Once PQ symmetry is broken the
associated particle, the QCD axion, is a plausible dark matter candidate.
Calculating the cosmological energy density of the axion requires
nonperturbative QCD input---the high-temperature topological susceptibility. I
will show results from a pure-glue calculation and examine the implications for
the axion mass and coupling.
