The Two-Loop Symbol of all Multi-Regge Regions

Understand

We study the symbol of the two-loop n-gluon MHV amplitude for all Mandelstam regions in multi-Regge kinematics in N=4 super Yang-Mills theory.

• While the number of distinct Mandelstam regions grows exponentially with n, the increase of independent symbols turns out to be merely quadratic.
• We uncover how to construct the symbols for any number of external gluons from just two building blocks which are naturally associated with the six- and seven-gluon amplitude, respectively.
• The second building block is entirely new, and in addition to its symbol, we also construct a prototype function that correctly reproduces all terms of maximal functional transcendentality.