Edge coalitions in graphs

An edge coalition in a graph $G=(V,E)$ consists of two disjoint sets of edges $E_1$ and $E_2$, neither of which is an edge dominating set but whose union $E_1\cup E_2$ is an edge dominating set. An edge coalition partition in a graph $G$ of order $n=|V|$ and size $m$ is an edge partition $\pi=\{E_1,\cdots,E_k\}$ so that every set $E_i$ of $\pi$ either is a singleton edge dominating set, or is not an edge dominating set but forms an edge coalition with another set $E_j$ which is not an edge dominating set. In this paper we introduce the concept of edge coalition and show that there exists edge coalition for some graphs and trees. The graphs $G$ with small and size number of edge coalition are characterized. Finally, coalition graphs of special graphs are studied.