Dear friends of FRAGMENT,

to decompress from the adrenaline high weekend of WAGS, we are very happy to have Rob Silversmith, from Warwick/MSRI, speak to us this week (at 3:15pm).

Given a bipartite graph G (subject to a simple constraint), the “cross-ratio degree” of G is a non-negative integer invariant of G, defined via a simple counting problem in algebraic geometry. I’ll discuss several natural contexts in which cross-ratio degrees arise, and discuss a combinatorial recursive algorithm for computing cross-ratio degrees (due to C. Goldner). I will also present a perhaps-surprising upper bound on cross-ratio degrees in terms of perfect matchings.