A note on r-equitable k-colorings of trees

A graph G = (V, E) is r-equitably k-colorable if there exists a partition of V into k independent sets V¹, V², ... , Vk such that | |Vi| − |Vj| | ≤ r for all i, j ∈ {1, 2, ... , k}. In this note, we show that if two trees T¹ and T² of order at least two are r-equitably k-colorable for r ≥ 1 and k ≥ 3, then all trees obtained by adding an arbitrary edge between T¹ and T² are also r-equitably k-colorable.

Mots clés

Trees, equitable coloring, independent sets