On automorphism groups of half-arc-transitive tetravalent graphs

Yuandong Li, Binzhou Xia, Jin-Xin Zhou

We characterize connected tetravalent graphs $\hat{I}“$ which admit groups $M<H$ of automorphisms such that $\hat{I}“$ is $M$-half-arc-transitive and $H$-arc-transitive. Examples for each case…