Almost-K\"ahler four manifolds with harmonic self-dual Weyl curvature

We show that a compact almost-K\"ahler four manifold $(M, g, \omega)$ with harmonic self-dual Weyl curvature and constant scalar curvature is K\"ahler if $c_{1}\cdot\omega\geq 0$. We also prove an integral curvature inequality for compact almost-K\"ahler four manifolds with harmonic self-dual Weyl curvature

Almost-K\"ahler four manifolds with nonnegative biorthogonal curvature

We classify compact almost-K\"ahler four manifolds with nonnegative biorthogonal curvature

Self-dual almost-K\"ahler four manifolds

We classify compact self-dual almost-K\"ahler four manifolds of positive type and zero type. In particular, using LeBrun's result, we show that any self-dual almost-K\"ahler metric on a manifold which is diffeomorphic to $\mathbb{CP}_{2}$ is the Fubini-Study metric up to rescaling. In case of negative type, we classify compact self-dual almost-K\"ahler four manifolds with $J$-invariant Ricci tensor