Discrete Mathematics ( IF 0.770 ) Pub Date : 2020-01-09 , DOI: 10.1016/j.disc.2019.111809 Jiaao Li; Xueliang Li; Meiling Wang
We prove that for a simple graph with , if , then either or its complementary graph has flow index strictly less than 3. This is proved by a newly developed closure operation, which may be useful in studying further flow index problems. In particular, our result supports a recent conjecture of Li et al. (2018), and improves a result of Hou et al. (2012) on nowhere-zero 3-flows.