Tree and 1-loop fundamental BCJ relations from soft theorems

Abstract

Abstract We provide a new derivation of the fundamental BCJ relation among double-color-ordered tree amplitudes of bi-adjoint scalar theory, based on the leading soft theorem for external scalars. Then, we generalize the fundamental BCJ relation to 1-loop Feynman integrands. We also use the fundamental BCJ relation to understand Adler’s zero for tree amplitudes of the nonlinear sigma model and Born–Infeld theory.