“…This approach is based on the description of the interacting hadrons in terms of partons, which together with the LSZ reduction formulas [3,4], and the eikonal approximation for propagators in an external field, leads to the Wilson-loop formalism for soft high energy scattering [5,6,7,8,9,10,11]. The resulting expressions for the scattering amplitudes have been investigated by means of various nonperturbative techniques, including the Stochastic Vacuum Model [5,6,8,10,11,12], the Instanton Liquid Model [13,14], the AdS/CFT correspondence for non-confining [15,16,17] and confining [18,19,20] backgrounds, and Lattice Gauge Theory [21,14,22], taking advantage, in most cases, of the analytic continuation of the amplitudes in Euclidean space [23,24,25,26,27,28,29]. These works are concerned with the leading behaviour of the elastic scattering amplitudes at high energy, and so non-vacuum Reggeon-exchange contributions are neglected from the onset.…”