On the Emerging Phenomenology of <(A_\mu)^2>

Abstract

We discuss phenomenology of the vacuum condensate <(A_\mu)^2> in pure gauge theories, where A_\mu is the gauge potential. Both Abelian and non-Abelian cases are considered. In case of the compact U(1) the non-perturbative part of the condensate <(A_\mu)^2> is saturated by monopoles. In the non-Abelian case, a two-component picture for the condensate is presented according to which finite values of order \Lambda_{QCD}^2 are associated both with large and short distances. We obtain a lower bound on the <(A_\mu)^2> by considering its change at the phase transition. Numerically, it produces an estimate similar to other measurements. Possible physical manifestations of the condensate are discussed.