We further develop the formalism of arXiv:0712.0159 for the approximate solution of the Nambu-Goto (NG) equations with polygon conditions in AdS backgrounds, which is needed in modern studies of the string/gauge duality. The inscribed-circle condition is preserved, which leaves only one unknown function y 0 (y 1 , y 2 ) to solve and considerably simplifies our presentation. The problem is to find a delicate balance -if not an exact match -between two different structures: the NG equation (a nonlinear deformation of the Laplace equation with solutions nonlinearly deviating from holomorphic functions) and the boundary ring associated with polygons formed from null segments in Minkowski space. We provide more details about the theory of these structures and suggest an extended class of functions to be used at the next stage of the Alday-Maldacena program: the evaluation of regularized NG actions. §1. IntroductionIn this paper we begin our consideration of the next class of approximate solutions to the Nambu-Goto (NG) equations with null-polygon boundary conditions by the method suggested in 1). This problem is important for the study of the string/gauge (AdS/CFT) duality, 2), 3) reformulated recently 4)−28) as an identity between regularized minimal areas in AdS 5 and BDS/DHKS/BHT 7), 8), 17), 29) amplitudes for gluon scattering in N = 4 SUSY YM. Unfortunately, even after this groundbreaking reformulation, 4) no explicit check of duality has been carried out, even in the leading order of the strong-coupling expansion because of the usual technical difficulties on the string side. In this particular case, the first difficult problem is finding an explicit solution to a special version of the Plateau minimal-surface problem, 30) i.e., to the NG equations in AdS 5 geometry with the boundary conditions at the AdS boundary represented by a polygon Π with n lightlike (null) segments. We refer the readers to 4) for an explanation of how this polygon emerges in the problem after a sequence of transformations,and to 13) and 23) for additional comments and the notation. Irrespective of these motivations, the current formulation of the gauge/string duality is now purely geoDownloaded from https://academic.oup.