Full-color three-loop three-point form factors in N=4 SYM.

We present the detailed computation of full-color three-loop three-point form factors of both stress-tensor supermultiplet and a length-three operator in N=4 SYM. The integrands are constructed based on the color-kinematics duality and generalized unitarity method. An interesting observation is that the CK-dual integrands contain a large number of free parameters. We discuss the origin of these free parameters in detail and check that they cancel after simplifying the integrands. We further perform a numerical evaluation of the integrals at a special kinematics point by using public packages FIESTA and pySecDec based on the sector-decomposition approach. While such a three-loop computation requires large computational resources, we find that one can significantly simplify the numerical computation by expressing the integrands in terms of uniformly transcendental integrals. Given the full-color numerical results, we are able to check the non-planar infrared divergences where the non-dipole terms firstly appear at three loops. The numerical planar finite remainder for the stress-tensor supermultiplet is consistent with the computation from form factor bootstrap. We also obtain for the first time the numerical three-loop non-planar remainder for the stress-tensor supermultiplet, as well as the three-loop remainder for the length-three operator.