Ramsey-type results for path covers and path partitions

Abstract

A family $\mathcal{P}$ of subgraphs of $G$ is called a {\it path cover} (resp. a {\it path partition}) of $G$ if $\bigcup _{P\in \mathcal{P}}V(P)=V(G)$ (resp. $\dot\bigcup _{P\in \mathcal{P}}V(P)=V(G)$) and every element of $\mathcal{P}$ is a path. The minimum cardinality of a path cover (resp. a path partition) of $G$ is denoted by ${\rm pc}(G)$ (resp. ${\rm pp}(G)$). In this paper, we characterize the forbidden subgraph conditions assuring us that ${\rm pc}(G)$ (or ${\rm pp}(G)$) is bounded by a constant. Our main results introduce a new Ramsey-type problem.