Solution to a problem on hamiltonicity of graphs under Ore- and Fan-type heavy subgraph conditions

TL;DR

This paper proves that certain heavy subgraph conditions involving claw-o-heavy and Z3-f-heavy properties guarantee Hamiltonicity in 2-connected graphs, answering a previously posed open problem.

Contribution

It establishes new sufficient conditions for Hamiltonicity based on Ore- and Fan-type heavy subgraph conditions, extending prior results.

Findings

Every 2-connected claw-o-heavy and Z3-f-heavy graph is Hamiltonian (except two graphs).

The result confirms a conjecture from previous research.

It generalizes and implies earlier theorems by Faudree et al. and Chen et al.

Abstract

A graph $G$ is called \emph{claw-o-heavy} if every induced claw ($K_{1,3}$) of $G$ has two end-vertices with degree sum at least $|V(G)|$ in $G$. For a given graph $R$, $G$ is called \emph{$R$-f-heavy} if for every induced subgraph $H$ of $G$ isomorphic to $R$ and every pair of vertices $u,v\in V(H)$ with $d_H(u,v)=2$, there holds $\max\{d(u),d(v)\}\geq |V(G)|/2$. In this paper, we prove that every 2-connected claw-\emph{o}-heavy and $Z_3$-\emph{f}-heavy graph is hamiltonian (with two exceptional graphs), where $Z_3$ is the graph obtained from identifying one end-vertex of $P_4$ (a path with 4 vertices) with one vertex of a triangle. This result gives a positive answer to a problem proposed in [B. Ning, S. Zhang, Ore- and Fan-type heavy subgraphs for Hamiltonicity of 2-connected graphs, Discrete Math. 313 (2013) 1715--1725], and also implies two previous theorems of Faudree et al. and Chen et al., respectively.