Let G be a graph without 4-cycles and 5-cycles. We show that the problem to determine whether G is (0,k)-colorable is NP-complete for each positive integer k. Moreover, we construct non-(1,k)-colorable planar graphs without 4-cycles and 5-cycles for each positive integer k. Finally, we prove that G is (d1,d2)-colorable where (d1,d2)=(4,4),(3,5), and (2,9).
@article{arxiv.1611.10239,
title = {Defective 2-colorings of planar graphs without 4-cycles and 5-cycles},
author = {Pongpat Sittitrai and Kittikorn Nakprasit},
journal= {arXiv preprint arXiv:1611.10239},
year = {2016}
}