Basic cohomology group decomposition of K-contact 5-manifolds

Abstract

In this paper, we consider decompositions of basic degree 2 cohomology for a compact K-contact 5-manifold $(M,ξ,η,Φ,g)$, and conclude the pureness and fullness of $Φ$-invariant and $Φ$-anti-invariant cohomology groups. Moreover, we discuss the decomposition of the complexified basic degree 2 cohomology group. This is an analogue problem when Draghici, Li and Zhang \cite{DLZ1} considered the $C^{\infty}$ pureness and fullness of $J$-invariant and $J$-anti-invariant subgroups of the degree 2 real cohomology group $H^2(M,\mathbb{R})$ of any compact almost complex manifold $(M, J)$.