A simpler way to compute cosmic particle collisions

Early-universe physics can be studied by computing four-point correlators describing how particles interact in near-de Sitter space. This calculation is notoriously messy in standard approaches but becomes tractable in the Grassmannian, a geometric structure encoding kinematic relationships. The authors derived closed-form expressions using hypergeometric functions and Legendre polynomials, showing Grassmannian formulas are far simpler than their momentum-space equivalents.