Cartesian products of graphs and their coherent configurations

Fuente: arXiv
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Autori principali: Cai, Jinzhuan, Guo, Jin, Gavrilyuk, Alexander L., Ponomarenko, Ilia
Natura: Preprint
Pubblicazione: 2024
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author Cai, Jinzhuan
Guo, Jin
Gavrilyuk, Alexander L.
Ponomarenko, Ilia
author_facet Cai, Jinzhuan
Guo, Jin
Gavrilyuk, Alexander L.
Ponomarenko, Ilia
contents The coherent configuration $\mathsf{WL}(X)$ of a graph $X$ is the smallest coherent configuration on the vertices of $X$ that contains the edge set of $X$ as a relation. The aim of the paper is to study $\mathsf{WL}(X)$ when $X$ is a Cartesian product of graphs. The example of a Hamming graph shows that, in general, $\mathsf{WL}(X)$ does not coincide with the tensor product of the coherent configurations of the factors. We prove that if $X$ is ``closed'' with respect to the $6$-dimensional Weisfeiler-Leman algorithm, then $\mathsf{WL}(X)$ is the tensor product of the coherent configurations of certain graphs related to the prime decomposition of $X$. This condition is trivially satisfied for almost all graphs. In addition, we prove that the property of a graph ``to be decomposable into a Cartesian product of $k$ connected prime graphs'' for some $k\ge 1$ is recognized by the $m$-dimensional Weisfeiler-Leman algorithm for all $m\ge 6$.
format Preprint
id arxiv_https___arxiv_org_abs_2411_02689
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Cartesian products of graphs and their coherent configurations
Cai, Jinzhuan
Guo, Jin
Gavrilyuk, Alexander L.
Ponomarenko, Ilia
Combinatorics
The coherent configuration $\mathsf{WL}(X)$ of a graph $X$ is the smallest coherent configuration on the vertices of $X$ that contains the edge set of $X$ as a relation. The aim of the paper is to study $\mathsf{WL}(X)$ when $X$ is a Cartesian product of graphs. The example of a Hamming graph shows that, in general, $\mathsf{WL}(X)$ does not coincide with the tensor product of the coherent configurations of the factors. We prove that if $X$ is ``closed'' with respect to the $6$-dimensional Weisfeiler-Leman algorithm, then $\mathsf{WL}(X)$ is the tensor product of the coherent configurations of certain graphs related to the prime decomposition of $X$. This condition is trivially satisfied for almost all graphs. In addition, we prove that the property of a graph ``to be decomposable into a Cartesian product of $k$ connected prime graphs'' for some $k\ge 1$ is recognized by the $m$-dimensional Weisfeiler-Leman algorithm for all $m\ge 6$.
title Cartesian products of graphs and their coherent configurations
topic Combinatorics
url https://arxiv.org/abs/2411.02689