Regions of Level $\ell$ of Catalan/Semiorder-Type Arrangements

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Hauptverfasser: Chen, Yanru, Wang, Suijie, Yang, Jinxing, Zhao, Chengdong
Format: Preprint
Veröffentlicht: 2024
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author Chen, Yanru
Wang, Suijie
Yang, Jinxing
Zhao, Chengdong
author_facet Chen, Yanru
Wang, Suijie
Yang, Jinxing
Zhao, Chengdong
contents In 1996, Stanley extended the classical Catalan arrangement and semiorder arrangement, which are called the Catalan-type arrangement $\mathcal{C}_{n,A}$ and the semiorder-type arrangement $\mathcal{C}_{n,A}^*$ in this paper. By establishing a labeled Dyck path model for the regions of $\mathcal{C}_{n,A}$ and $\mathcal{C}_{n,A}^*$, this paper explores several enumerative problems related to the number of regions of level $\ell$, denoted as $r_{\ell}(\mathcal{C}_{n,A})$ and $r_{\ell}(\mathcal{C}_{n,A}^*)$, which includes: (1) proving a Stirling convolution relation between $r_{\ell}(\mathcal{C}_{n,A})$ and $r_{\ell}(\mathcal{C}_{n,A}^*)$, refining a result by Stanley and Postnikov; (2) showing that the sequences$\left(r_\ell{(\mathcal{C}_{n,A})}\right)_{n\geq 0}$ and $(r_\ell {(\mathcal{C}_{n,A}^*)})_{n\geq 0}$ exhibit properties of binomial type in the sense of Rota; (3) establishing the transformational significance of $r_{\ell}(\mathcal{C}_{n,A})$ and $r_{\ell}(\mathcal{C}_{n,A}^*)$ under Stanley's ESA framework: they can be viewed as transition matrices from binomial coefficients to their characteristic polynomials respectively. Further, we present two applications of the theories and methods: first, we provide a hyperplane arrangement counting interpretation of the two-parameter generalization of Fuss--Catalan numbers, which is closely related to the number of regions of level $\ell$ in the $m$-Catalan arrangement. Second, using labeled Dyck paths to depict the number of regions in the $m$-Catalan arrangement, we algorithmically provide the inverse mapping of the Fu, Wang, and Zhu mapping.
format Preprint
id arxiv_https___arxiv_org_abs_2410_10198
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Regions of Level $\ell$ of Catalan/Semiorder-Type Arrangements
Chen, Yanru
Wang, Suijie
Yang, Jinxing
Zhao, Chengdong
Combinatorics
05B35, 52C35
In 1996, Stanley extended the classical Catalan arrangement and semiorder arrangement, which are called the Catalan-type arrangement $\mathcal{C}_{n,A}$ and the semiorder-type arrangement $\mathcal{C}_{n,A}^*$ in this paper. By establishing a labeled Dyck path model for the regions of $\mathcal{C}_{n,A}$ and $\mathcal{C}_{n,A}^*$, this paper explores several enumerative problems related to the number of regions of level $\ell$, denoted as $r_{\ell}(\mathcal{C}_{n,A})$ and $r_{\ell}(\mathcal{C}_{n,A}^*)$, which includes: (1) proving a Stirling convolution relation between $r_{\ell}(\mathcal{C}_{n,A})$ and $r_{\ell}(\mathcal{C}_{n,A}^*)$, refining a result by Stanley and Postnikov; (2) showing that the sequences$\left(r_\ell{(\mathcal{C}_{n,A})}\right)_{n\geq 0}$ and $(r_\ell {(\mathcal{C}_{n,A}^*)})_{n\geq 0}$ exhibit properties of binomial type in the sense of Rota; (3) establishing the transformational significance of $r_{\ell}(\mathcal{C}_{n,A})$ and $r_{\ell}(\mathcal{C}_{n,A}^*)$ under Stanley's ESA framework: they can be viewed as transition matrices from binomial coefficients to their characteristic polynomials respectively. Further, we present two applications of the theories and methods: first, we provide a hyperplane arrangement counting interpretation of the two-parameter generalization of Fuss--Catalan numbers, which is closely related to the number of regions of level $\ell$ in the $m$-Catalan arrangement. Second, using labeled Dyck paths to depict the number of regions in the $m$-Catalan arrangement, we algorithmically provide the inverse mapping of the Fu, Wang, and Zhu mapping.
title Regions of Level $\ell$ of Catalan/Semiorder-Type Arrangements
topic Combinatorics
05B35, 52C35
url https://arxiv.org/abs/2410.10198