摘要: The light-like cusp anomalous dimension is a universal function that controls infrared divergences
in quite general quantum field theories. In the maximally supersymmetric Yang-Mills theory this
function is fixed fully by integrability to the three-loop order. At four loops a non-planar correction
appears which we obtain for the first time from a numerical computation of the Sudakov form
factor. Key ingredients are widely applicable methods to control the number-theoretic aspects of
the appearing integrals. Our result shows explicitly that quadratic Casimir scaling breaks down at
four loops.