Quarkonium bound state equation in the Wilson loop approach with minimal   surfaces
  Wilson loop averages are evaluated for large contours and in the large N limit by means of minimal surfaces. This allows the study of the quark-antiquark gauge invariant Green function through its dependence on Wilson loops. A covariant bound state equation is derived which in the center-of-mass frame and at equal-times takes the form of a Breit-Salpeter type equation. The interaction potentials reduce in the static case to a confining linear vector potential. For moving quarks, flux tube like contributions are present. The nonrelativistic limit is considered. 
F. Jugeau and H. Sazdjian