摘要: Form factors of composite operators in the SL(2) sector of N = 4 SYM theory are
studied up to two loops via the on-shell unitarity method. The non-compactness of
this subsector implies the novel feature and technical challenge of an unlimited number
of loop momenta in the integrand’s numerator. At one loop, we derive the full minimal
form factor to all orders in the dimensional regularisation parameter. At two loops, we
construct the complete integrand for composite operators with an arbitrary number of
covariant derivatives, and we obtain the remainder functions as well as the dilatation
operator for composite operators with up to three covariant derivatives. The remainder
functions reveal curious patterns suggesting a hidden maximal uniform transcendentality
for the full form factor. Finally, we speculate about an extension of these patterns
to QCD.