All two-loop MHV remainder functions in multi-Regge kinematics

Understand

We introduce a method to extract the symbol of the coefficient of $(2\pi i)^2$ of MHV remainder functions in planar N=4 Super Yang-Mills in multi-Regge kinematics region directly from the symbol in full kinematics.

• At two loops this symbol can be uplifted to the full function in a unique way, without any beyond-the-symbol ambiguities.
• We can therefore determine all two-loop MHV amplitudes at function level in all kinematic regions with different energy signs in multi-Regge kinematics.
• We analyse our results and we observe that they are consistent with the hypothesis of a contribution from the exchange of a three-Reggeon composite state starting from two loops and eight points in certain kinematic regions.