Calculating the quantum probability of colliding subatomic particles once required drawing thousands of pages of tedious Feynman diagrams; Alexander Postnikov mapped multi-dimensional geometric shapes whose volume directly gives particle scattering probabilities. Published in Advances in Mathematics, Postnikov’s positive Grassmannian cells became the mathematical foundation of the Amplituhedron, suggesting that space and time are emergent illusions of pure geometry.

In high-energy particle physics, calculating what happens when two gluons smash together inside the Large Hadron Collider required physicists to calculate hundreds of pages of quantum Feynman diagrams, producing millions of terms that miraculously canceled out to a simple two-line answer.
MIT mathematician Alexander Postnikov discovered a jewel of pure mathematics: totally positive Grassmann cells. By mapping these shapes using planar spider-web graphs, theoretical physicists discovered that the volume of these geometric crystals calculates particle collision probabilities instantly without ever mentioning space or time.
This paper united pure algebraic combinatorics with quantum gravity. By eliminating millions of lines of algebra in particle physics, by founding the physics of the Amplituhedron, and by suggesting that spacetime is an emergent projection of geometry, positive geometry reshapes modern physics.
Enumeration of totally positive Grassmann cells
Postnikov (Webs in totally positive Grassmann cells, in preparation) has given a combinatorially explicit cell decomposition of the totally nonnegative part of a Grassmannian, denoted Grk,n+, and showed that this set of cells is isomorphic as a graded poset to many other interesting graded posets. The main result of our work is an explicit generating function which enumerates the cells in Grk,n+ according to their dimension. As a corollary, we give a new proof that the Euler characteristic of Grk,n+ is 1. Additionally, we use our result to produce a new q-analog of the Eulerian numbers, which interpolates between the Eulerian numbers, the Narayana numbers, and the binomial coefficients.
Ask this paper your own questions, or keep browsing the verified research catalogue.