On the volume of a pseudo-effective class and semi-positive properties of the Harder-Narasimhan filtration on a compact Hermitian manifold

Abstract

This paper divides into two parts. Let $(X,ω)$ be a compact Hermitian manifold. Firstly, if the Hermitian metric $ω$ satisfies the assumption that $\partial\overline{\partial}ω^k=0$ for all $k$, we generalize the volume of the cohomology class in the Kähler setting to the Hermitian setting, and prove that the volume is always finite and the Grauert-Riemenschneider type criterion holds true, which is a partial answer to a conjecture posed by Boucksom. Secondly, we observe that if the anticanonical bundle $K^{-1}_X$ is nef, then for any $\varepsilon>0$, there is a smooth function $ϕ_\varepsilon$ on $X$ such that $ω_\varepsilon:=ω+i\partial\overline{\partial}ϕ_\varepsilon>0$ and Ricci$(ω_\varepsilon)\geq-\varepsilonω_\varepsilon$. Furthermore, if $ω$ satisfies the assumption as above, we prove that for a Harder-Narasimhan filtration of $T_X$ with respect to $ω$, the slopes $μ_ω(\mathcal{F}_i/\mathcal{F}_{i-1})\geq 0$ for all $i$, which generalizes a result of Cao which plays a very important role in his studying of the structures of Kähler manifolds.