In the present talk I will introduce a new class of almost contact metric manifolds, called anti-quasi-Sasakian (aqS for short). They are non-normal almost contact metric manifolds $(M,φ,ξ,η,g)$, locally fibering along the 1-dimensional foliation generated by $ξ$ onto Kähler manifolds endowed with a closed 2-form of type (2,0). Various examples of anti-quasi-Sasakian manifolds will be provided, including compact nilmanifolds, $\mathbb{S}^1$-bundles and manifolds admitting a $\operatorname{Sp}(n)\times \{1\}$-reduction of the structural group of the frame bundle. Then, I will discuss some geometric obstructions to the existence of aqS structures, mainly related to curvature and topological properties. In particular, I will focus on compact manifolds endowed with aqS structures of maximal rank, showing that they cannot be homogeneous and they must satisfy some restrictions on the Betti numbers.

This is based on joint works with Giulia Dileo (Bari) and Ivan Yudin (Coimbra).

References

1. D. Di Pinto, On anti-quasi-Sasakian manifolds of maximal rank J. Geom. Phys. 200 (2024), Paper no. 105174, 10 pp.
2. D. Di Pinto, G. Dileo, Anti-quasi-Sasakian manifolds, Ann. Global Anal. Geom. 64 (1), Article no. 5 (2023), 35 pp.