Characterization of Sasakian manifolds

Abstract: Weak contact metric manifolds, i.e., the linear complex structure on the contact distribution is replaced by a nonsingular skew-symmetric tensor, defined by the author and R. Wolak, allowed us to take a new look at the theory of contact manifolds. In this paper, we continue our study, see arXiv:2312.11411, of a structure of this type, called a weak nearly Sasakian structure, and prove two theorems characterizing Sasakian manifolds. Our main result generalizes the theorem by A. Nicola - G. Dileo - I. Yudin (2018) and provides a new criterion for a weak almost contact metric manifold to be Sasakian.