Characteristic Polynomials and Hypergraph Generating Functions via Heaps of Pieces

Fuente: arXiv
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Autori principali: Cooper, Joshua, Guo, Krystal, Okur, Utku
Natura: Preprint
Pubblicazione: 2024
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author Cooper, Joshua
Guo, Krystal
Okur, Utku
author_facet Cooper, Joshua
Guo, Krystal
Okur, Utku
contents It is a classical result due to Jacobi in algebraic combinatorics that the generating function of closed walks at a vertex $u$ in a graph $G$ is determined by the rational function \[ \frac{ϕ_{G-u}(t)}{ϕ_G(t)} \] where $ϕ_G(t)$ is the characteristic polynomial of $G$. In this paper, we show that the corresponding rational function for a hypergraph is also a generating function for some combinatorial objects in the hypergraph. We make use of the Heaps of Pieces framework, developed by Viennot, demonstrating its use on graphs, digraphs, and multigraphs before using it on hypergraphs. In the case of a graph $G$, the pieces are cycles and the concurrence relation is sharing a vertex. The pyramids with maximal piece containing a vertex $u \in V(G)$ are in one-to-one correspondence with closed walks at $u$. In the case of a hypergraph $\mathcal{H}$, connected "infragraphs" can be defined as the set of pieces, with the same concurrence relation: sharing a vertex. Our main results are established by analyzing multivariate resultants of polynomial systems associated to adjacency hypermatrices.
format Preprint
id arxiv_https___arxiv_org_abs_2411_03567
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Characteristic Polynomials and Hypergraph Generating Functions via Heaps of Pieces
Cooper, Joshua
Guo, Krystal
Okur, Utku
Combinatorics
05C65 (Primary) 05C50, 05A15, 15A69 (Secondary)
It is a classical result due to Jacobi in algebraic combinatorics that the generating function of closed walks at a vertex $u$ in a graph $G$ is determined by the rational function \[ \frac{ϕ_{G-u}(t)}{ϕ_G(t)} \] where $ϕ_G(t)$ is the characteristic polynomial of $G$. In this paper, we show that the corresponding rational function for a hypergraph is also a generating function for some combinatorial objects in the hypergraph. We make use of the Heaps of Pieces framework, developed by Viennot, demonstrating its use on graphs, digraphs, and multigraphs before using it on hypergraphs. In the case of a graph $G$, the pieces are cycles and the concurrence relation is sharing a vertex. The pyramids with maximal piece containing a vertex $u \in V(G)$ are in one-to-one correspondence with closed walks at $u$. In the case of a hypergraph $\mathcal{H}$, connected "infragraphs" can be defined as the set of pieces, with the same concurrence relation: sharing a vertex. Our main results are established by analyzing multivariate resultants of polynomial systems associated to adjacency hypermatrices.
title Characteristic Polynomials and Hypergraph Generating Functions via Heaps of Pieces
topic Combinatorics
05C65 (Primary) 05C50, 05A15, 15A69 (Secondary)
url https://arxiv.org/abs/2411.03567