Component factors in $K_{1,r}$-free graphs

TL;DR

This paper establishes minimum degree conditions for $K_{1,r}$-free graphs to contain specific spanning subgraphs called factors, including paths and star-based factors, and provides sharpness examples for these conditions.

Contribution

It introduces new minimum degree criteria for $K_{1,r}$-free graphs to possess various factors and covers, extending existing graph factor theory.

Findings

Minimum degree conditions for $ ext{S}_n$-factors in $K_{1,r}$-free graphs

Criteria for $ ext{P}_{ ext{geq} 3}$-factors in such graphs

Examples demonstrating the sharpness of the results

Abstract

A graph is said to be $K_{1,r}$-free if it does not contain an induced subgraph isomorphic to $K_{1,r}$. An $\mathcal{F}$-factor is a spanning subgraph $H$ such that each connected component of $H$ is isomorphic to some graph in $\mathcal{F}$. In particular, $H$ is called an $\{P_2,P_3\}$-factor of $G$ if $\mathcal{F}=\{P_2,P_3\}$; $H$ is called an $\mathcal{S}_n$-factor of $G$ if $\mathcal{F}=\{K_{1,1},K_{1,2},K_{1,3},...,K_{1,n}\}$, where $n\geq2$. A spanning subgraph of a graph $G$ is called a $\mathcal{P}_{\geq k}$-factor of $G$ if its each component is isomorphic to a path of order at least $k$, where $k\geq2$. A graph $G$ is called a $\mathcal{F}$-factor covered graph if there is a $\mathcal{F}$-factor of $G$ including $e$ for any $e\in E(G)$. In this paper, we give a minimum degree condition for a $K_{1,r}$-free graph to have an $\mathcal{S}_n$-factor and a $\mathcal{P}_{\geq 3}$-factor, respectively. Further, we obtain sufficient conditions for $K_{1,r}$-free graphs to be $\mathcal{P}_{\geq 2}$-factor, $\mathcal{P}_{\geq 3}$-factor or $\{P_2,P_3\}$-factor covered graphs. In addition, examples show that our results are sharp.