<i>Y</i>-system for scattering amplitudes

Abstract

We compute N=4 Super Yang Mills planar amplitudes at strong coupling by\nconsidering minimal surfaces in AdS_5 space. The surfaces end on a null\npolygonal contour at the boundary of AdS. We show how to compute the area of\nthe surfaces as a function of the conformal cross ratios characterizing the\npolygon at the boundary. We reduce the problem to a simple set of functional\nequations for the cross ratios as functions of the spectral parameter. These\nequations have the form of Thermodynamic Bethe Ansatz equations. The area is\nthe free energy of the TBA system. We consider any number of gluons and in any\nkinematic configuration.\n