Paper and ancilary files.
Carlos R. Mafra
Tree-level double-color-ordered amplitudes are computed using Berends–Giele recursion relations applied to the bi-adjoint cubic scalar theory. The standard notion of Berends–Giele currents is generalized to double-currents and their recursions are derived from a perturbiner expansion of linearized fields that solve the non-linear field equations. Two applications are given. Firstly, we prove that the entries of the inverse KLT matrix are equal to Berends–Giele double-currents (and are therefore easy to compute). And secondly, a simple formula to generate tree-level BCJ-satisfying numerators for arbitrary multiplicity is proposed by evaluating the field-theory limit of tree-level string amplitudes for various color orderings using double-color-ordered amplitudes.