Geometry and Asymptotics of Schubert Polynomials, Graph Colorings, and Flows on Graphs

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Three fundamental and challenging problems in mathematics inspired from real-world activities are to count the number of ways of transporting goods through a network, sorting a list of tasks, and scheduling jobs to time slots. Some instances of these counting problems are difficult to count exactly and one can instead study bounds, asymptotics, and large-scale behaviors of these numbers as well as using geometric structures encoding the objects that are counted. Abstractly these problems can be studied with the following mathematical objects: "integer flows on a graph", "Schubert polynomials of permutations", and "graph vertex colorings", respectively that have connections to other fields of mathematics and other areas like computer science, and physics.More concretely, this project studies problems in enumerative, algebraic, and asymptotic combinatorics with connections to representation theory and geometry. The project has three parts. The first part is about finding a ¨q-analogue¨ of a constant term identity of Zeilberger to compute volumes of flow polytopes and establishing a connection between this identity and the famous Selberg integral. The second part is about studying the large-scale behavior of Schubert and Grothendieck polynomials using existing combinatorial models like rc-graphs, bumpless pipe dreams, and excited diagrams. The last part is about studying chromatic symmetric functions of Dyck paths, which are the object of the famous Stanley--Stembridge--Shareshian--Wachs conjecture. The PI will study the Newton polytope, Lorentzian property, and connections to q-rook theory of these symmetric functions. Students will be trained during the course of this project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.