On the Significance of the Quantity "A Squared"
  We consider the gauge potential A and argue that the minimum value of the volume integral of A squared (in Euclidean space) may have physical meaning, particularly in connection with the existence of topological structures. A lattice simulation comparing compact and non-compact ``photodynamics'' shows a jump in this quantity at the phase transition, supporting this idea. 
F.V.Gubarev, L. Stodolsky, V.I. Zakharov