On nonperturbative calculation of hadron field correlators

An approximate method is treated for calculating correlation functions for hadron field operators in QCD including the 1/Nc expansion and quasiclassical approximation. One the base of this method, an effective two-dimensional action for hadron correlators is suggested. Variation of the action leads to the Yang-Mills equations with dynamical boundary conditions which take into account the presence of quarks. Solution of these equations describes a bare relativistic string with quarks at its ends. It is shown that the moving string produces a surface which has a constant scalar curvature and is embedded into four-dimensional Euclidean space. The contribution introduced by the above field configuration into the correlator agrees with the area law and does not vanish in the limit Nc → ∞