Employing the little group symmetry within the spinor-helicity formalism to constrain scattering amplitudes

Abstract: This thesis aims to describe the little group scaling and how it simplifies the calculation of scattering amplitudes. The little group has the defining property that it leaves a particular four-momentum invariant, which is used to describe how the internal structure of a particle is transformed under the little group. An important part in the study of little group scaling is the spinor-helicity formalism, which is based on spinors of helicity h = ±1/2. This formalism comes with some interesting identities which already simplify the calculation of amplitudes. Finally, we show that applying little group scaling to massless particles with complex momenta in the spinor-helicity formalism fully constrains their (mathematical) three-particle amplitudes.