Gromov hyperbolicity of minor graphs

TL;DR

This paper investigates how the Gromov hyperbolicity constant of a graph changes when edges are deleted or contracted, providing insights into the hyperbolicity of minor graphs.

Contribution

It offers quantitative analysis of hyperbolicity constant distortion under edge deletion and contraction, focusing on minor graphs.

Findings

Hyperbolicity constants are affected in quantifiable ways by edge removal.

Results apply to understanding hyperbolicity in graph minors.

Provides bounds and relations for hyperbolicity after graph transformations.

Abstract

If $X$ is a geodesic metric space and $x_1,x_2,x_3\in X$, a geodesic triangle $T=\{x_1,x_2,x_3\}$ is the union of the three geodesics $[x_1x_2]$, $[x_2x_3]$ and $[x_3x_1]$ in $X$. The space $X$ is $\delta$-hyperbolic (in the Gromov sense) if any side of $T$ is contained in a $\delta$-neighborhood of the union of the two other sides, for every geodesic triangle $T$ in $X$. The study of hyperbolic graphs is an interesting topic since the hyperbolicity of a geodesic metric space is equivalent to the hyperbolicity of a graph related to it. In the context of graphs, to remove and to contract an edge of a graph are natural transformations. The main aim in this work is to obtain quantitative information about the distortion of the hyperbolicity constant of the graph $G \setminus e$ (respectively, $\,G/e\,$) obtained from the graph $G$ by deleting (respectively, contracting) an arbitrary edge $e$ from it. This work provides information about the hyperbolicity constant of minor graphs.