On minimal graphs containing k perfect matchings

TL;DR

This paper characterizes minimally k-matchable graphs as disjoint unions of odd subdivisions of a finite set of graphs and copies of K2, providing a structural understanding of graphs with exactly k perfect matchings.

Contribution

It introduces a finite set of base graphs whose odd subdivisions generate all minimally k-matchable graphs, advancing the structural theory of perfect matchings.

Findings

Existence of a finite set S(k) for each k>0

Characterization of minimally k-matchable graphs as unions involving S(k)

Structural description involving odd subdivisions and copies of K2

Abstract

We call a finite undirected graph minimally k-matchable if it has at least k distinct perfect matchings but deleting any edge results in a graph which has not. An odd subdivision of some graph G is any graph obtained by replacing every edge of G by a path of odd length connecting its end vertices such that all these paths are internally disjoint. We prove that for every k>0 there exists a finite set of graphs S(k) such that every minimally k-matchable graph is isomorphic to a disjoint union of an odd subdivision of some graph from S(k) and any number of copies of the complete graph on two vertices.