Lorentz structure of confinement in QCD

The problem of the Lorentz structure of confinement in 3+1 QCD for a system formed by a quark and a static antiquark has been studied in the limit of a large number of colors, and it has found that the confining force between them is substantially nonlocal. The heavy-quark limit has been discussed in detail, and it is demonstrated that the effective interaction leads to a local linearly growing potential such that 5/6 of it is a Lorentz scalar and 1/6 is a Lorentz vector. Corrections to the leading regime that include those that do not depend on spin and which result from the time-nonlocality of interaction and from quark Z graphs have been found. By considering the example of the two-dimensional 't Hooft model, the features of the opposite limiting case (string limit) and the chiral properties of the model have been discussed