A determination of Aμ2 and the non-perturbative vacuum energy of Yang–Mills theory in the Landau gauge

We discuss the 2-point-particle-irreducible (2PPI) expansion, which sums bubble graphs to all orders, in the context of SU(N) Yang–Mills theory in the Landau gauge. Using the method we investigate the possible existence of a gluon condensate of mass dimension two, 〈AμaAμa〉, and the corresponding non-zero vacuum energy. This condensate gives rise to a dynamically generated mass for the gluon.