Compatible Recurrent Identities of the Sandpile Group and Maximal Stable Configurations

TL;DR

This paper explores the structure of recurrent configurations in the abelian sandpile model, focusing on graphs with compatible recurrent identities and the complete maximal identity property, and demonstrates how to construct such graphs.

Contribution

It introduces the concept of compatible recurrent identities across different sinks and shows how to construct graphs with the complete maximal identity property by attaching trees.

Findings

Graphs with compatible recurrent identities can be constructed by attaching trees.

Graphs with the complete maximal identity property can be achieved through specific graph modifications.

Several conjectures about the property in graph products are proposed.

Abstract

In the abelian sandpile model, recurrent chip configurations are of interest as they are a natural choice of coset representatives under the quotient of the reduced Laplacian. We investigate graphs whose recurrent identities with respect to different sinks are compatible with each other. The maximal stable configuration is the simplest recurrent chip configuration, and graphs whose recurrent identities equal the maximal stable configuration are of particular interest, and are said to have the complete maximal identity property. We prove that given any graph $G$ one can attach trees to the vertices of $G$ to yield a graph with the complete maximal identity property. We conclude with several intriguing conjectures about the complete maximal identity property of various graph products.