The sphaleron rate from 4D Euclidean lattices

Abstract

We develop a new method to determine thermal activation rates, such as for bubble nucleation, topology change, etc., using 4-dimensional Euclidean methods. This allows nonperturbative study on the lattice. We then investigate the strong sphaleron rate in pure-glue QCD at temperatures between 1.3 Tc and 1000 Tc, making contact with previous results but extending them down close to the critical temperature. The extension to full QCD will be straightforward. Limitations of the proposal (the inability to compute a certain dynamical prefactor, puzzling large-volume behavior, and the inability to treat temperatures T < 1.3 Tc) are also discussed.