Published online by Cambridge University Press: 24 August 2023
We classify fibrations of abstract $3$-regular GKM graphs over
$2$-regular ones, and show that all fibrations satisfying the known necessary conditions for realizability are, in fact, realized as the projectivization of equivariant complex rank-
$2$ vector bundles over quasitoric
$4$-manifolds or
$S^4$. We investigate the existence of invariant (stable) almost complex, symplectic, and Kähler structures on the total space. In this way, we obtain infinitely many Kähler manifolds with Hamiltonian non-Kähler actions in dimension
$6$ with prescribed one-skeleton, in particular with a prescribed number of isolated fixed points.