Joint Theory Seminar: Christoph Bartsch

Title: Recursion Relations for One-loop Goldstone Boson Amplitudes

Abstract:
In recent years modern amplitude methods have been successfully applied to the study of exceptional (scalar) effective field theories. In these theories tree-level amplitudes are completely fixed from consistent factorization and their soft behavior (Adler zero). As a consequence, the tree-level S-Matrix can be recursively computed to all multiplicities from on-shell data alone. This is known as the soft bootstrap.
In this talk I want to discuss the extension of these recursive techniques to the 1-loop planar integrand in the non-linear sigma model (NLSM). First, I will show that the integrand is no longer fixed by cuts and  soft limits alone. Instead, the key to obtaining a unique integrand will be to study its single-cuts. I will propose an extended softness criterion for the single-cuts that will lead to a unique definition of the integrand suitable for on-shell recursion.