(10.11.) Compatibility of Landau Singularities
Hofie Hannesdottir (IAS Princeton)
10.11.2022 at 16:15
The analytic properties of scattering amplitudes place nontrivial constraints on their structure. For example, solutions to the Landau equations characterize where amplitudes are allowed to have singularities and branch points. In recent years, significant advances have been made in using analytic-structure constraints for amplitude computations. For instance, computations of certain classes of polylogarithmic Feynman integrals have exploited the Steinmann relations, which forbid sequential discontinuities in partially overlapping momentum channels. In this talk, we present several classes of constraints on the allowed singularity structure and sequential discontinuities of Feynman integrals. While some of the relations are generic, others present simplifications for polylogarithmic integrals, and yet others constrain amplitudes in physical-kinematic regions. We show that these types of constraints go beyond the Steinmann relations, and work out their implications in some examples. In addition to algebraic formulations, we show how the constraints can be expressed as a collection of graphical rules that allows one to determine whether or not specific sequences of discontinuities can be nonzero in Feynman integrals of a given topology.
via ZOOM