Higher matching complexes of complete graphs and complete bipartite graphs

TL;DR

This paper determines the homotopy types of higher matching complexes for complete graphs and bipartite graphs, revealing they are homotopy equivalent to spheres of specific dimensions.

Contribution

It provides a closed-form formula for the homotopy type of the (n-2)-matching complex of complete graphs and proves the (n-1)-matching complex of complete bipartite graphs is homotopy equivalent to a sphere.

Findings

Homotopy type of (n-2)-matching complex of complete graphs derived.

(n-1)-matching complex of K_{n,n} is homotopy equivalent to a sphere.

Explicit sphere dimension for bipartite case established.

Abstract

For $r\geq 1$, the $r$-matching complex of a graph $G$, denoted $M_r(G)$, is a simplicial complex whose faces are the subsets $H \subseteq E(G)$ of the edge set of $G$ such that the degree of any vertex in the induced subgraph $G[H]$ is at most $r$. In this article, we give a closed form formula for the homotopy type of the $(n-2)$-matching complex of complete graph on $n$ vertices. We also prove that the $(n-1)$-matching complex of complete bipartite graph $K_{n,n}$ is homotopy equivalent to a sphere of dimension $(n-1)^2-1$.