Colour singlet ensemble

Abstract

The author considers a statistical ensemble of gluons constrained to be colour singlet at high temperatures. This naturally leads us to consider the grand canonical partition function with an imaginary chemical potential. It is demonstrated that up to two loops the constrained colour singlet ensemble is thermodynamically equivalent to the unconstrained one, neglecting surface effects. The author also evaluates the free energy of heavy quarks or the thermal Wilson loop up to two loops. It is realised that in the confinement phase charged gluons behave as fermions.