Screened perturbation theory for 3d Yang-Mills theory and the magnetic modes of hot QCD

Original · EN

Perturbation theory for non-abelian gauge theories at finite temperature is plagued by infrared divergences which are caused by magnetic soft modes g²T, corresponding to gluon fields of a 3d Yang-Mills theory. While the divergences can be regulated by a dynamically generated magnetic mass on that scale, the gauge coupling drops out of the effective expansion parameter requiring summation of all loop orders for the calculation of observables. Some gauge invariant possibilities to implement such infrared-safe resummations are reviewed. We use a scheme based on the non-linear sigma model to estimate some of the contributions g⁶ of the soft magnetic modes to the QCD pressure through two loops. The NLO contribution amounts to 10% of the LO, suggestive of a reasonable convergence of the series.