Tutte Colloquium - Freddy Cachazo

Title: Combinatorics in Particle Interactions

Abstract:

The main approach for testing physical theories of particles is via scattering experiments. The traditional approach for computing theoretical predictions uses Feynman diagrams. However, the number of terms produced in such computations grows so fast that even simple processes require computer assistance. 

In this talk, I will give an introduction to on-shell diagrams. These new diagrams re-sum Feynman diagrams into surprisingly compact formulas. On-shell diagrams naturally appear in the study of the positroid, the combinatorial structure on the totally non-negative Grassmannian, and connect physical properties to cluster algebras.