In the approach, the on-shell scattering process "tree" is described by a positive Grassmannian, a structure in algebraic geometry analogous to a convex polytope, that generalizes the idea of a simplex in projective space.
In geometry, a Hanner polytope is a convex polytope constructed recursively by Cartesian product and polar dual operations.
Balinski's theorem, which he published in 1961, gives a lower bound on the graph-theoretic connectivity of every convex polytope.