On the Lorentz nature of confinement

The Lorentz structure of the long-range confining force in the heavy quark approximation is studied within the model of QCD vacuum which is described by the bilocal gluonic correlators and assures the area law asymptotics for the isolated Wilson loop. The effective Dirac-type equation is written out for the quark propagating in such vacuum in the presence of static antiquark source. In the heavy quark limit the effective interaction is reduced to the potential one, with 5/6 Lorentz scalar and 1/6 Lorentz vector linear confinement. The next-to-leading in √(σ)/m corrections are calculated, and the sign and the coefficient at the spin-orbit term is found to be in agreement with both Eichten-Feinberg-Gromes results and demands of heavy quarkonia phenomenology