Bases of massless EFTs via momentum twistors

Understand

I present a novel method of deriving a basis of contact terms in massless effective field theories (EFTs).

• It relies on the parametrization of $N$-body kinematics via the so-called momentum twistors.
• A basis is constructed directly at the amplitude level, without using fields or Lagrangians.
• The method consists in recasting any local contact term as a sum of rational functions built from Lorentz-invariant contractions of momentum twistors.