Perturbiner Methods for Effective Field Theories and the Double Copy

Understand

Perturbiner expansion provides a generating function for all Berends-Giele currents in a given quantum field theory.

• We apply this method to various effective field theories with and without color degrees of freedom.
• In the colored case, we study the U(N) non-linear sigma model of Goldstone bosons (NLSM) in a recent parametrization due to Cheung and Shen, as well as its extension involving a coupling to the bi-adjoint scalar.
• We propose a Lagrangian and a Cachazo-He-Yuan formula for the latter valid in multi-trace sectors and systematically calculate its amplitudes.