Supergravity amplitudes, the double copy, and ultraviolet behavior

In this chapter, we present a scattering-amplitudes perspective on supergravity and describe its application to the study of ultraviolet properties of supergravity theories at high-loop orders. The basic on-shell tools that make such calculations feasible are reviewed, including generalized unitarity, color-kinematics duality, and the double-copy construction. We also outline the web of theories connected by the double copy. The results of various calculations of potential ultraviolet divergences are summarized. These include puzzling enhanced ultraviolet cancellations, for which no symmetry-based understanding currently exists, showing that there is much more to learn about the ultraviolet properties of supergravity theories. Finally, we comment on future calculations that should help resolve the puzzles.