EPP Theory Seminar: Mao Zeng: Generalized unitarity and frontiers of perturbative QFT
Perturbative QFT plays a pivotal role in theoretical predictions for particle colliders and gravitational wave interferometry experiments. In both cases, continued upgrades and planned future experiments are challenging the achievable precision of theoretical calculations. Generalized unitarity is a central method of the modern program of scattering amplitudes, which bypasses Feynman diagrams to efficiently construct loop integrands. By analyzing the geometry of unitarity cut surfaces, we promote generalized unitarity to be a powerful tool for multi-loop integration. Combined with the use of numerical ansatzes, we achieve several results at the frontiers of perturbative QFT, e.g. two-loop five-point amplitudes in QCD and supersymmetric theories, needed for modeling high-multiplicity final-states at the LHC, and third-post-Minkowskian potential between non-spinning massive objects in gravity, which defied attacks by classical GR methods.