The 2-loop generalized scaling function from the BES/FRS equation

Abstract

We formulate the BES/FRS equation as a functional equation in the rapidity space and perform its strong coupling expansion in the limit when $\ell=j/4g$ is kept finite. We obtain a result which is consistent with the previous calculations at tree level and one loop and which differs from the two-loop calculation in 0805.4615 by a term singular at $\ell=0$.