On the Ehrhart polynomial of Schubert matroids. (English) Zbl 1532.05030

Fan, Neil J. Y.; Li, Yao

Discrete Comput. Geom. 71, No. 2, 587-626 (2024).

Summary: In this paper, we give a formula for the number of lattice points in the dilations of Schubert matroid polytopes. As applications, we obtain the Ehrhart polynomials of uniform and minimal matroids as special cases, and give a recursive formula for the Ehrhart polynomials of \((a, b)\)-Catalan matroids. Ferroni showed that uniform and minimal matroids are Ehrhart positive. We show that all sparse paving Schubert matroids are Ehrhart positive and their Ehrhart polynomials are coefficient-wisely bounded by those of minimal and uniform matroids. This confirms a conjecture of Ferroni for the case of sparse paving Schubert matroids. Furthermore, we introduce notched rectangle matroids, which include minimal matroids, sparse paving Schubert matroids and panhandle matroids. We show that three subfamilies of notched rectangle matroids are Ehrhart positive, and conjecture that all notched rectangle matroids are Ehrhart positive.

MSC:

05B35	Combinatorial aspects of matroids and geometric lattices
52B40	Matroids in convex geometry (realizations in the context of convex polytopes, convexity in combinatorial structures, etc.)
52B20	Lattice polytopes in convex geometry (including relations with commutative algebra and algebraic geometry)
14N15	Classical problems, Schubert calculus

Keywords:

Schubert matroids; Ehrhart polynomials; lattice path matroids; matroid polytopes

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