Pfaffian Diagrams for Gluon Tree Amplitudes

Understand

Pfaffian diagrams are formulated to represent gluon amplitudes computed from the Cachazo-He-Yuan (CHY) formula.

• They may be regarded as a systematic regrouping of Feynman diagrams after internal momenta are expanded and products of vertex factors are evaluated.
• This reprocessing enables gluon amplitudes expressed in Pfaffian diagrams to contain less terms.
• For example, there are 19 terms for the four-point amplitude in Pfaffian diagrams, and 35 terms in Feynman diagrams.