An analytic result for the two-loop seven-point MHV amplitude in N=4 SYM

We describe a general algorithm which builds on several pieces of data available in the literature to construct explicit analytic formulas for two-loop MHV amplitudes in N = 4 super-Yang-Mills theory. The non-classical part of an amplitude is built from A(3) cluster polylogarithm functions; classical polylogarithms with (negative) cluster X-coordinate arguments are added to complete the symbol of the amplitude; beyond-the-symbol terms proportional to pi(2) are determined by comparison with the differential of the amplitude; and the overall additive constant is fixed by the collinear limit. We present an explicit formula for the seven-point amplitude R-7((2)) as a sample application.