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On the Ehrhart Polynomial of Schubert Matroids

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Abstract

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.

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Acknowledgements

The authors wish to thank the referees for their valuable comments and suggestions. We are grateful to Shaoshi Chen, Peter Guo, Lisa Sun, Matthew Xie, Sherry Yan, and Arthur Yang for helpful conversations. Yao Li would like to thank the Research Experience for Undergraduates (REU) program “Sparklet” of the Math Department at Sichuan University. This work was supported by the National Natural Science Foundation of China (Grant Nos. 11971250 and 12071320) and Sichuan Science and Technology Program (Grant No. 2020YJ0006).

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  1. Department of Mathematics, Sichuan University, Chengdu, 610064, People’s Republic of China

    Neil J. Y. Fan & Yao Li

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  1. Neil J. Y. Fan
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Correspondence to Neil J. Y. Fan.

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Fan, N.J.Y., Li, Y. On the Ehrhart Polynomial of Schubert Matroids. Discrete Comput Geom 71, 587–626 (2024). https://doi.org/10.1007/s00454-023-00495-z

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