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3 The domain of definition of the complex Monge-Ampère operator. [0297]

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3 The domain of definition of the complex Monge-Ampère operator.

We start with a few definitions.

Definition 1

Let XX be a compact complex manifold of complex dimension nn, let χ∈H1,1​(X,ℝ)\chi\in H^{1,1}(X,\mathbb{R}) be a pseudoeffective class, let ω>0\omega>0 be a hermitian form and let (Uα)α(U_{\alpha})_{\alpha} be a finite covering of coordinate starshaped open sets. We denote by M​AχMA_{\chi} the set of closed positive (1,1)(1,1)-currents γ∈χ\gamma\in\chi such that

−∫Uαhαγk∧ωn−k<+∞,-\int\limits_{U_{\alpha}}h_{\alpha}\gamma^{k}\wedge\omega^{n-k}<+\infty\,,

with γ=i​∂∂¯​hα\gamma=i\partial\bar{\partial}h_{\alpha}, supUαhα=0\sup_{U_{\alpha}}h_{\alpha}=0 and γk:=i​∂∂¯​(hα​γk−1)\gamma^{k}:=i\partial\bar{\partial}(h_{\alpha}\gamma^{k-1}) over UαU_{\alpha}, for all k=1,…,n−1k=1,...,n-1.

It is clear by the definition that the closed positive currents γk\gamma^{k}, for k=1,…,nk=1,...,n are globally well defined. Consider now γ≥0\gamma\geq 0 be a closed positive (1,1)(1,1)-current with continuous local potentials. We define

𝒫^γ:={φ∈𝒫γ|γ+i​∂∂¯​φ∈M​A{γ}}.\hat{\cal P}_{\gamma}:=\left\{\varphi\in{\cal P}_{\gamma}\,|\,\gamma+i\partial\bar{\partial}\varphi\in MA_{\{\gamma\}}\right\}\,.

Let φ∈𝒫^γ\varphi\in\hat{\cal P}_{\gamma} with zero Lelong numbers. It is well known from the first author work (which becomes drastically simple in this particular case) the existence of a family (φε)ε>0(\varphi_{\varepsilon})_{\varepsilon>0}, φε∈𝒫γ+ε​ω∩C∞​(X)\varphi_{\varepsilon}\in{\cal P}_{\gamma+\varepsilon\omega}\cap C^{\infty}(X), such that φε↓φ\varphi_{\varepsilon}\downarrow\varphi as ε↓0+\varepsilon\downarrow 0^{+}. In the case φ∈𝒫γ∩C0​(X)\varphi\in{\cal P}_{\gamma}\cap C^{0}(X) the convergence of φε\varphi_{\varepsilon} is also uniform. We have the following crucial result.

Theorem 5

(Degenerate monotone convergence result).
Let (X,ω)(X,\omega) be a polarized compact Kähler manifold of complex dimension nn and let γ\gamma, TT be closed positive (1,1)(1,1)-currents with continuous local potentials. Then the following statements hold true.
A) For all φ∈𝒫^γ\varphi\in\hat{\cal P}_{\gamma}, φ≤0\varphi\leq 0 and k,l≥0k,l\geq 0, k+l≤nk+l\leq n, k≤n−1k\leq n-1

∫X−φγφk∧Tl∧ωn−k−l<+∞,\int\limits_{X}-\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l}<+\infty\,,

B) Let φ∈𝒫^γ\varphi\in\hat{\cal P}_{\gamma}, φ≤0\varphi\leq 0 with zero Lelong numbers and φε∈𝒫γ+ε​ω∩C∞​(X)\varphi_{\varepsilon}\in{\cal P}_{\gamma+\varepsilon\omega}\cap C^{\infty}(X), such that φε↓φ\varphi_{\varepsilon}\downarrow\varphi as ε→0+\varepsilon\rightarrow 0^{+}. Then for all k,l≥0k,l\geq 0, k+l≤nk+l\leq n, k≤n−1k\leq n-1

φε​(γφε+ε​ω)k∧Tl⟶φ​γφk∧Tl,\displaystyle\varphi_{\varepsilon}\,(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k}\wedge T^{l}\longrightarrow\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\,, (3.1)
(γφε+ε​ω)k+1∧Tl⟶γφk+1∧Tl,\displaystyle(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k+1}\wedge T^{l}\longrightarrow\gamma_{\varphi}^{k+1}\wedge T^{l}\,, (3.2)

weakly as ε→0+\varepsilon\rightarrow 0^{+}. Moreover γφk∧Tl=Tl∧γφk\gamma_{\varphi}^{k}\wedge T^{l}=T^{l}\wedge\gamma_{\varphi}^{k} for all φ∈𝒫^γ\varphi\in\hat{\cal P}_{\gamma} and k,l≥0k,l\geq 0, k+l≤nk+l\leq n.

As follows immediately from the proof, the statement of this theorem still holds if we replace TlT^{l} with a product T1∧….∧TlT_{1}\wedge....\wedge T_{l}, where the currents TjT_{j} have the same properties as TT. As a matter of fact, we wrote the statement in the previous special case only for the sake of notation simplicity. However during the proof it is useful to consider that statements concerning terms involving TlT^{l} are still valid if we replace TlT^{l} with γr∧Tl−r\gamma^{r}\wedge T^{l-r}.

Proof. Statement (3.2) follows from (3.1) by using the weak continuity of the i​∂∂¯i\partial\bar{\partial} operator and an induction on (3.2). We remark that claim 2 asserts statement A) in full generality for k=0k=0. We denote by Ak,lA_{k,l} the assertion A) in the statement of the theorem for the relative indices (k,l)(k,l). For all k=0,…,n−1k=0,...,n-1 and l=0,…,n−kl=0,...,n-k we define the following statement Bk,lB_{k,l}: for all p=0,…,kp=0,...,k

φε​γφp∧(γφε+ε​ω)k−p∧Tl⟶φ​γφk∧Tl,\displaystyle\varphi_{\varepsilon}\,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p}\wedge T^{l}\longrightarrow\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\,, (3.3)
i​∂∂¯​φε∧γφp∧(γφε+ε​ω)k−p∧Tl⟶i​∂∂¯​φ∧γφk∧Tl,\displaystyle i\partial\bar{\partial}\varphi_{\varepsilon}\wedge\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p}\wedge T^{l}\longrightarrow i\partial\bar{\partial}\varphi\wedge\gamma_{\varphi}^{k}\wedge T^{l}\,, (3.4)
γφp∧(γφε+ε​ω)k−p+1∧Tl⟶γφk+1∧Tl,\displaystyle\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p+1}\wedge T^{l}\longrightarrow\gamma_{\varphi}^{k+1}\wedge T^{l}\,, (3.5)
φ​γφp∧(γφε+ε​ω)k−p∧Tl⟶φ​γφk∧Tl,,\displaystyle\varphi\,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p}\wedge T^{l}\longrightarrow\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\,,\,, (3.6)

weakly as ε→0+\varepsilon\rightarrow 0^{+} and

γφk+1∧Tl=Tl∧γφk+1.\displaystyle\gamma_{\varphi}^{k+1}\wedge T^{l}=T^{l}\wedge\gamma_{\varphi}^{k+1}\,. (3.7)

We remark that (3.4) follows from (3.3) by the weak continuity of the i​∂∂¯i\partial\bar{\partial} operator. By combining (3.4) with the weak continuity of the i​∂∂¯i\partial\bar{\partial} operator we obtain

(γφε+ε​ω)∧γφp∧(γφε+ε​ω)k−p∧Tl⟶γφk+1∧Tl,(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)\wedge\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p}\wedge T^{l}\longrightarrow\gamma_{\varphi}^{k+1}\wedge T^{l}\,,

weakly as ε→0+\varepsilon\rightarrow 0^{+}. On the other hand (3.7)p−1,∙\eqref{SymWeg}_{p-1,\bullet} implies

(γφε+ε​ω)∧γφp∧(γφε+ε​ω)k−p∧Tl\displaystyle(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)\wedge\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p}\wedge T^{l} =\displaystyle= (γφε+ε​ω)k−p+1∧Tl∧γφp\displaystyle(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p+1}\wedge T^{l}\wedge\gamma_{\varphi}^{p}
=\displaystyle= γφp∧(γφε+ε​ω)k−p+1∧Tl.\displaystyle\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p+1}\wedge T^{l}\,.

In this way we deduce (3.5). The symmetry identity (3.7) follows from (3.5) for p=0p=0 and from the fact that

Tl∧(γφε+ε​ω)k+1⟶Tl∧γφk+1,T^{l}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k+1}\longrightarrow T^{l}\wedge\gamma_{\varphi}^{k+1}\,,

weakly as ε→0+\varepsilon\rightarrow 0^{+}. This last convergence statement follows by combining (3.5) for p=l=0p=l=0 with an induction on ll by means of the weak continuity of the i​∂∂¯i\partial\bar{\partial} operator.
We now prove simultaneously the statements Ak,lA_{k,l} and Bk,lB_{k,l}, l=0,…,n−kl=0,...,n-k by using an induction on k=0,…,n−1k=0,...,n-1. For the moment we assume that the potential φ\varphi in statement A) also has zero Lelong numbers, but we will get rid of this hypothesis at the end. Statements A0,∙A_{0,\bullet} and B0,∙B_{0,\bullet} are true by claim 2 and its proof. So we assume that these statements hold for j≤k−1j\leq k-1 and we prove them for kk. The induction process is divided in two main steps.

Step I. This step consists in proving the

Claim 5

. If Aj,∙A_{j,\bullet} and Bj,∙B_{j,\bullet} hold true for all j=0,…,k−1j=0,...,k-1, then Ak,lA_{k,l} implies Bk,lB_{k,l}, with l=0,…,n−kl=0,...,n-k.

As pointed out before in order to prove Bk,lB_{k,l} is sufficient to show (3.3) and (3.6). The proof of (3.6) is quite similar to the proof of (3.3) that we now explain. We first prove by induction on s=0,…,k−ps=0,...,k-p the inequality

∫X−φεγφp∧(γφε+εω)k−p∧Tl∧ωn−k−l\displaystyle\int\limits_{X}-\varphi_{\varepsilon}\,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p}\wedge T^{l}\wedge\omega^{n-k-l} (3.8)
≤\displaystyle\leq ∫X−φγφp+s∧(γφε+εω)k−p−s∧Tl∧ωn−k−l\displaystyle\int\limits_{X}-\varphi\,\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s}\wedge T^{l}\wedge\omega^{n-k-l}
+\displaystyle+ ∑r=0s−1∫X(φε−φ)​γφp+r∧(γφε+ε​ω)k−p−r−1∧γ∧Tl∧ωn−k−l\displaystyle\sum_{r=0}^{s-1}\;\int\limits_{X}(\varphi_{\varepsilon}-\varphi)\,\gamma_{\varphi}^{p+r}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-r-1}\wedge\gamma\wedge T^{l}\wedge\omega^{n-k-l}
−\displaystyle- ∑r=0s−1∫Xε​φ​γφp+r∧(γφε+ε​ω)k−p−r−1∧Tl∧ωn−k−l+1.\displaystyle\sum_{r=0}^{s-1}\;\int\limits_{X}\varepsilon\varphi\,\gamma_{\varphi}^{p+r}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-r-1}\wedge T^{l}\wedge\omega^{n-k-l+1}.

Inequality (3.8) is obviously true for s=0s=0. (Here we adopt the usual convention of neglecting a sum when it runs over an empty set of indices.) Before procedding to the proof of inequality (3.8), we need to point out two useful remarks.

1) Let α\alpha be a smooth closed real (q,q)(q,q)-form, RR e a closed positive (r,r)(r,r)-current, v≥0v\geq 0 be a measurable function such that ∫Xv​R∧ωn−r<+∞\int_{X}vR\wedge\omega^{n-r}<+\infty. This implies that the currents i​∂∂¯​v∧R:=i​∂∂¯​(v​R)i\partial\bar{\partial}v\wedge R:=i\partial\bar{\partial}(v\,R) and i​∂∂¯​v∧α∧R:=i​∂∂¯​(v​α∧R)i\partial\bar{\partial}v\wedge\alpha\wedge R:=i\partial\bar{\partial}(v\alpha\wedge R) are well defined. Then the Leibnitz formula implies

α∧i​∂∂¯​v∧R=i​∂∂¯​v∧α∧R.\displaystyle\alpha\wedge i\partial\bar{\partial}v\wedge R=i\partial\bar{\partial}v\wedge\alpha\wedge R\,. (3.9)

2) Thanks to the inductive hypothesis Aj,∙A_{j,\bullet}, j≤k−1j\leq k-1 we have

∫X−φγφp+r∧γh∧Tl∧ωn−p−r−h−l<+∞\int\limits_{X}-\varphi\,\gamma_{\varphi}^{p+r}\wedge\gamma^{h}\wedge T^{l}\wedge\omega^{n-p-r-h-l}<+\infty

for all h=0,…,k−p−r−1h=0,...,k-p-r-1. By (3.9) this implies

∫X−φγφp+r∧(γφε+εω)k−p−r−1∧Tl∧ωn−k−l+1<+∞,\int\limits_{X}-\varphi\,\gamma_{\varphi}^{p+r}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-r-1}\wedge T^{l}\wedge\omega^{n-k-l+1}<+\infty\,,

so the current

S:=φ​γφp+r∧(γφε+ε​ω)k−p−r−1∧TlS:=\varphi\,\gamma_{\varphi}^{p+r}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-r-1}\wedge T^{l}

is well defined and we can define the current

i​∂∂¯​φ∧γφp+r∧(γφε+ε​ω)k−p−r−1∧Tl:=i​∂∂¯​S.i\partial\bar{\partial}\varphi\wedge\gamma_{\varphi}^{p+r}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-r-1}\wedge T^{l}:=i\partial\bar{\partial}S\,.

Then the integration by parts formula

∫Xi​∂∂¯​φε∧S∧ωn−k−l=∫Xφε​i​∂∂¯​S∧ωn−k−l\int\limits_{X}i\partial\bar{\partial}\varphi_{\varepsilon}\wedge S\wedge\omega^{n-k-l}\;=\;\int\limits_{X}\varphi_{\varepsilon}\,i\partial\bar{\partial}S\wedge\omega^{n-k-l}

writes explicitly as

∫Xi​∂∂¯​φε∧φ​γφp+r∧(γφε+ε​ω)k−p−r−1∧Tl∧ωn−k−l\displaystyle\int\limits_{X}i\partial\bar{\partial}\varphi_{\varepsilon}\wedge\varphi\,\gamma_{\varphi}^{p+r}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-r-1}\wedge T^{l}\wedge\omega^{n-k-l} (3.10)
=\displaystyle= ∫Xφε​i​∂∂¯​φ∧γφp+r∧(γφε+ε​ω)k−p−r−1∧Tl∧ωn−k−l.\displaystyle\;\int\limits_{X}\varphi_{\varepsilon}\,i\partial\bar{\partial}\varphi\wedge\gamma_{\varphi}^{p+r}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-r-1}\wedge T^{l}\wedge\omega^{n-k-l}\,.

We suppose now inequality (3.8) true for ss and we prove it for s+1s+1. We start by expanding, thanks to formula (3.9), the integral

I\displaystyle I :⁣=\displaystyle:= ∫X−φγφp+s∧(γφε+εω)k−p−s∧Tl∧ωn−k−l\displaystyle\int\limits_{X}-\varphi\,\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s}\wedge T^{l}\wedge\omega^{n-k-l}
=\displaystyle= ∫X−φγφp+s∧(γ+εω)∧(γφε+εω)k−p−s−1∧Tl∧ωn−k−l\displaystyle\int\limits_{X}-\varphi\,\gamma_{\varphi}^{p+s}\wedge(\gamma+\varepsilon\omega)\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\omega^{n-k-l}
+\displaystyle+ ∫X−φγφp+s∧i∂∂¯φε∧(γφε+εω)k−p−s−1∧Tl∧ωn−k−l\displaystyle\int\limits_{X}-\varphi\,\gamma_{\varphi}^{p+s}\wedge i\partial\bar{\partial}\varphi_{\varepsilon}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\omega^{n-k-l}
=\displaystyle= ∫X−εφγφp+s∧(γφε+εω)k−p−s−1∧Tl∧ωn−k−l+1\displaystyle\int\limits_{X}-\varepsilon\varphi\,\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\omega^{n-k-l+1}
−\displaystyle- ∫Xφ​γφp+s∧(γφε+ε​ω)k−p−s−1∧γ∧Tl∧ωn−k−l\displaystyle\int\limits_{X}\varphi\,\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge\gamma\wedge T^{l}\wedge\omega^{n-k-l}
−\displaystyle- ∫Xi​∂∂¯​φε∧φ​γφp+s∧(γφε+ε​ω)k−p−s−1∧Tl∧ωn−k−l.\displaystyle\int\limits_{X}i\partial\bar{\partial}\varphi_{\varepsilon}\wedge\varphi\,\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\omega^{n-k-l}\,.

By applying the integration by parts formula (3.10) to the last integral we deduce

I\displaystyle I =\displaystyle= ∫X−φεγφp+s+1∧(γφε+εω)k−p−s−1∧Tl∧ωn−k−l\displaystyle\int\limits_{X}-\varphi_{\varepsilon}\,\gamma_{\varphi}^{p+s+1}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\omega^{n-k-l}
+\displaystyle+ ∫Xφε​γ∧γφp+s∧(γφε+ε​ω)k−p−s−1∧Tl∧ωn−k−l\displaystyle\int\limits_{X}\varphi_{\varepsilon}\,\gamma\wedge\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\omega^{n-k-l}
−\displaystyle- ∫Xφ​γφp+s∧(γφε+ε​ω)k−p−s−1∧γ∧Tl∧ωn−k−l\displaystyle\int\limits_{X}\varphi\,\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge\gamma\wedge T^{l}\wedge\omega^{n-k-l}
−\displaystyle- ∫Xε​φ​γφp+s∧(γφε+ε​ω)k−p−s−1∧Tl∧ωn−k−l+1.\displaystyle\int\limits_{X}\varepsilon\varphi\,\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\omega^{n-k-l+1}\,.

By combining the main (k−1)(k-1)-inductive hypothesis (3.7)j,∙\eqref{SymWeg}_{j,\,\bullet} , in Bj,∙B_{j,\,\bullet}, for j≤k−1j\leq k-1 with formula (3.9) we get

γ∧γφp+s∧(γφε+ε​ω)k−p−s−1∧Tl\displaystyle\gamma\wedge\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l} =\displaystyle= γ∧(γφε+ε​ω)k−p−s−1∧Tl∧γφp+s\displaystyle\gamma\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\gamma_{\varphi}^{p+s}
=\displaystyle= (γφε+ε​ω)k−p−s−1∧γ∧Tl∧γφp+s\displaystyle(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge\gamma\wedge T^{l}\wedge\gamma_{\varphi}^{p+s}
=\displaystyle= γφp+s∧(γφε+ε​ω)k−p−s−1∧γ∧Tl.\displaystyle\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge\gamma\wedge T^{l}\,.

By plugging this into the previous expression of II we obtain

I\displaystyle I =\displaystyle= ∫X−φεγφp+s+1∧(γφε+εω)k−p−s−1∧Tl∧ωn−k−l\displaystyle\int\limits_{X}-\varphi_{\varepsilon}\,\gamma_{\varphi}^{p+s+1}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\omega^{n-k-l}
+\displaystyle+ ∫X(φε−φ)​γφp+s∧(γφε+ε​ω)k−p−s−1∧γ∧Tl∧ωn−k−l\displaystyle\int\limits_{X}(\varphi_{\varepsilon}-\varphi)\,\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge\gamma\wedge T^{l}\wedge\omega^{n-k-l}
−\displaystyle- ∫Xε​φ​γφp+s∧(γφε+ε​ω)k−p−s−1∧Tl∧ωn−k−l+1\displaystyle\int\limits_{X}\varepsilon\varphi\,\gamma_{\varphi}^{p+s}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p-s-1}\wedge T^{l}\wedge\omega^{n-k-l+1}

which implies inequality (3.8) for s+1s+1. The inequality (3.8) for s=k−ps=k-p rewrites as

∫X−φεγφp∧(γφε+εω)k−p∧Tl∧ωn−k−l≤∫X−φγφk∧Tl∧ωn−k−l\displaystyle\int\limits_{X}-\varphi_{\varepsilon}\,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p}\wedge T^{l}\wedge\omega^{n-k-l}\;\leq\;\int\limits_{X}-\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l}
+\displaystyle+ ∑r=pk−1∫X(φε−φ)​γφr∧(γφε+ε​ω)k−r−1∧γ∧Tl∧ωn−k−l\displaystyle\sum_{r=p}^{k-1}\;\int\limits_{X}(\varphi_{\varepsilon}-\varphi)\,\gamma_{\varphi}^{r}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-r-1}\wedge\gamma\wedge T^{l}\wedge\omega^{n-k-l}
−\displaystyle- ∑r=pk−1∫Xε​φ​γφr∧(γφε+ε​ω)k−r−1∧Tl∧ωn−k−l+1.\displaystyle\sum_{r=p}^{k-1}\;\int\limits_{X}\varepsilon\varphi\,\gamma_{\varphi}^{r}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-r-1}\wedge T^{l}\wedge\omega^{n-k-l+1}\,.

By using the convergence inductive hypothesis (3.3)j,∙\eqref{Mcv3}_{j,\bullet}, (3.6)j,∙\eqref{Mcv4}_{j,\bullet} in Bj,∙B_{j,\bullet} for j≤k−1j\leq k-1 we deduce

lim supε→0+∫X−φεγφp∧(γφε+εω)k−p∧Tl∧ωn−k−l\displaystyle\limsup_{\varepsilon\rightarrow 0^{+}}\int\limits_{X}-\varphi_{\varepsilon}\,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p}\wedge T^{l}\wedge\omega^{n-k-l}
≤∫X−φγφk∧Tl∧ωn−k−l<+∞,\displaystyle\leq\int\limits_{X}-\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l}<+\infty\,, (3.11)

since we suppose Ak,lA_{k,l} true. (We can always arrange φε≤0\varphi_{\varepsilon}\leq 0 for all ε∈(0,1)\varepsilon\in(0,1) by changing φ\varphi into φ−C\varphi-C.) Thus by weak compactness of the mass there exists a sequence (εj)j(\varepsilon_{j})_{j}, εj↓0+\varepsilon_{j}\downarrow 0^{+} and a current of order zero Θ∈𝒟n−k−l,n−k−l′​(X)\Theta\in{\cal D}^{\prime}_{n-k-l,n-k-l}(X) such that

φεj​γφp∧(γφεj+εj​ω)k−p∧Tl⟶Θ,\varphi_{\varepsilon_{j}}\,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon_{j}}}+\varepsilon_{j}\,\omega)^{k-p}\wedge T^{l}\longrightarrow\Theta\,,

weakly as j→+∞j\rightarrow+\infty. So for any strongly positive (n−k,n−k)(n-k,n-k)-form α\alpha, we have

φεj​γφp∧(γφεj+εj​ω)k−p∧Tl∧α⟶Θ∧α,\varphi_{\varepsilon_{j}}\,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon_{j}}}+\varepsilon_{j}\,\omega)^{k-p}\wedge T^{l}\wedge\alpha\longrightarrow\Theta\wedge\alpha\,,

weakly as j→+∞j\rightarrow+\infty. The fact that φεj↓φ\varphi_{\varepsilon_{j}}\downarrow\varphi and

γφp∧(γφεj+εj​ω)k−p∧Tl∧α⟶γφk∧Tl∧α,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon_{j}}}+\varepsilon_{j}\,\omega)^{k-p}\wedge T^{l}\wedge\alpha\longrightarrow\gamma_{\varphi}^{k}\wedge T^{l}\wedge\alpha\,,

weakly as j→+∞j\rightarrow+\infty, by the convergence inductive hypothesis (3.5)k−1,l\eqref{Mcv32}_{k-1,l}, implies

Θ∧α≤φ​γφk∧Tl∧α,\Theta\wedge\alpha\leq\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\alpha\,,

thanks to lemma (3.9), page 189 in [Dem1]. Thus Θ≤φ​γφk∧Tl\Theta\leq\varphi\,\gamma_{\varphi}^{k}\wedge T^{l} . Combining this with the inequality (3.11) we obtain

∫XΘ∧ωn−k−l\displaystyle\int\limits_{X}\Theta\wedge\omega^{n-k-l} ≤\displaystyle\leq ∫Xφ​γφk∧Tl∧ωn−k−l\displaystyle\int\limits_{X}\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l}
≤\displaystyle\leq lim infε→0+∫Xφε​γφp∧(γφε+ε​ω)k−p∧Tl∧ωn−k−l\displaystyle\liminf_{\varepsilon\rightarrow 0^{+}}\int\limits_{X}\varphi_{\varepsilon}\,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k-p}\wedge T^{l}\wedge\omega^{n-k-l}
≤\displaystyle\leq limj→+∞∫Xφεj​γφp∧(γφεj+εj​ω)k−p∧Tl∧ωn−k−l\displaystyle\lim_{j\rightarrow+\infty}\int\limits_{X}\varphi_{\varepsilon_{j}}\,\gamma_{\varphi}^{p}\wedge(\gamma_{\varphi_{\varepsilon_{j}}}+\varepsilon_{j}\,\omega)^{k-p}\wedge T^{l}\wedge\omega^{n-k-l}
=\displaystyle= ∫XΘ∧ωn−k−l.\displaystyle\int\limits_{X}\Theta\wedge\omega^{n-k-l}\,.

We deduce Trω⁡(φ​γφk∧Tl−Θ)=0\operatorname{Tr}_{\omega}(\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}-\Theta)=0, which implies φ​γφk∧Tl=Θ\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}=\Theta since 0≤φ​γφk∧Tl−Θ0\leq\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}-\Theta. This proves statement Bk,lB_{k,l}.

Step II. This step consists in proving

Claim 6

. If Aj,∙A_{j,\bullet} and Bj,∙B_{j,\bullet} hold true for all j=0,…,k−1j=0,...,k-1, then Ak,lA_{k,l} hold also true for all l=0,…,n−kl=0,...,n-k.

We prove this claim by induction on l=0,…,n−kl=0,...,n-k. For l=0l=0 the conclusion follows from the hypothesis φ∈𝒫^γ\varphi\in\hat{\cal P}_{\gamma}. So we assume Ak,l−1A_{k,l-1} and we prove Ak,lA_{k,l}. For this purpose set T=θ+i​∂∂¯​uT=\theta+i\partial\bar{\partial}u, with θ\theta smooth and uu continuous and expand the integral

∫X−φε(γφε+εω)k∧Tl∧ωn−k−l\displaystyle\int\limits_{X}-\varphi_{\varepsilon}(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k}\wedge T^{l}\wedge\omega^{n-k-l}
=\displaystyle= ∫X−φε(γφε+εω)k∧Tl−1∧θ∧ωn−k−l\displaystyle\int\limits_{X}-\varphi_{\varepsilon}(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k}\wedge T^{l-1}\wedge\theta\wedge\omega^{n-k-l}
−\displaystyle- ∫Xu​i​∂∂¯​φε∧(γφε+ε​ω)k∧Tl−1∧ωn−k−l\displaystyle\int\limits_{X}u\,i\partial\bar{\partial}\varphi_{\varepsilon}\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k}\wedge T^{l-1}\wedge\omega^{n-k-l}
=\displaystyle= ∫X−φε(γφε+εω)k∧Tl−1∧θ∧ωn−k−l\displaystyle\int\limits_{X}-\varphi_{\varepsilon}(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k}\wedge T^{l-1}\wedge\theta\wedge\omega^{n-k-l}
−\displaystyle- ∫Xu​(γφε+ε​ω)k+1∧Tl−1∧ωn−k−l\displaystyle\int\limits_{X}u\,(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k+1}\wedge T^{l-1}\wedge\omega^{n-k-l}
+\displaystyle+ ∫Xu⁡(γ+ε​ω)∧(γφε+ε​ω)k∧Tl−1∧ωn−k−l.\displaystyle\int\limits_{X}u\,(\gamma+\varepsilon\omega)\wedge(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k}\wedge T^{l-1}\wedge\omega^{n-k-l}\,.

Hypothesis Ak,l−1A_{k,l-1} implies by step I

(γφε+ε​ω)k+1∧Tl−1⟶γφk+1∧Tl−1,(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k+1}\wedge T^{l-1}\longrightarrow\gamma_{\varphi}^{k+1}\wedge T^{l-1}\,,

weakly as ε→0+\varepsilon\rightarrow 0^{+}. Thus by taking the limit as ε→0+\varepsilon\rightarrow 0^{+} in the previous identity and by combining the inductive hypothesis (3.5)k−1,l−1\eqref{Mcv32}_{k-1,l-1} for p=0p=0 with the weak continuity of the i​∂∂¯i\partial\bar{\partial} operator, we deduce

limε→0+∫X−φε(γφε+εω)k∧Tl∧ωn−k−l\displaystyle\lim_{\varepsilon\rightarrow 0^{+}}\int\limits_{X}-\varphi_{\varepsilon}(\gamma_{\varphi_{\varepsilon}}+\varepsilon\omega)^{k}\wedge T^{l}\wedge\omega^{n-k-l}
=\displaystyle= ∫X−φγφk∧Tl−1∧θ∧ωn−k−l\displaystyle\int\limits_{X}-\varphi\,\gamma_{\varphi}^{k}\wedge T^{l-1}\wedge\theta\wedge\omega^{n-k-l}
−\displaystyle- ∫Xu​γφk+1∧Tl−1∧ωn−k−l\displaystyle\int\limits_{X}u\,\gamma_{\varphi}^{k+1}\wedge T^{l-1}\wedge\omega^{n-k-l}
+\displaystyle+ ∫Xu​γ∧γφk∧Tl−1∧ωn−k−l<+∞.\displaystyle\int\limits_{X}u\,\gamma\wedge\gamma_{\varphi}^{k}\wedge T^{l-1}\wedge\omega^{n-k-l}<+\infty\,.

By weak compactness of the mass we infer the existence of a sequence (εj)j(\varepsilon_{j})_{j}, εj↓0+\varepsilon_{j}\downarrow 0^{+} and a current of order zero Ξ∈𝒟n−k−l,n−k−l′​(X)\Xi\in{\cal D}^{\prime}_{n-k-l,n-k-l}(X) such that

φεj​(γφεj+εj​ω)k∧Tl⟶Ξ,\varphi_{\varepsilon_{j}}(\gamma_{\varphi_{\varepsilon_{j}}}+\varepsilon_{j}\,\omega)^{k}\wedge T^{l}\longrightarrow\Xi\,,

weakly as j→+∞j\rightarrow+\infty. In particular

φεj​(γφεj+εj​ω)k∧Tl∧ωn−k−l⟶Ξ∧ωn−k−l,\varphi_{\varepsilon_{j}}(\gamma_{\varphi_{\varepsilon_{j}}}+\varepsilon_{j}\,\omega)^{k}\wedge T^{l}\wedge\omega^{n-k-l}\longrightarrow\Xi\wedge\omega^{n-k-l}\,,

weakly as j→+∞j\rightarrow+\infty. The fact that φεj↓φ\varphi_{\varepsilon_{j}}\downarrow\varphi and

(γφεj+εj​ω)k∧Tl∧ωn−k−l⟶γφk∧Tl∧ωn−k−l,(\gamma_{\varphi_{\varepsilon_{j}}}+\varepsilon_{j}\,\omega)^{k}\wedge T^{l}\wedge\omega^{n-k-l}\longrightarrow\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l}\,,

weakly as j→+∞j\rightarrow+\infty, by the convergence (k−1)(k-1)-inductive hypothesis (3.5)k−1,l\eqref{Mcv32}_{k-1,l}, p=0p=0 in the statement Bk−1,lB_{k-1,l}, implies

Ξ∧ωn−k−l≤φ​γφk∧Tl∧ωn−k−l,\Xi\wedge\omega^{n-k-l}\leq\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l}\,,

thanks to lemma (3.9), page 189 in [Dem1]. We conclude

∫X−φγφk∧Tl∧ωn−k−l≤−∫XΞ∧ωn−k−l<+∞.\displaystyle\int\limits_{X}-\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l}\leq-\int\limits_{X}\Xi\wedge\omega^{n-k-l}<+\infty\,.


End of the proof. In the case the Lelong numbers of φ\varphi are not zero we replace in the previous computations γ\gamma with γ+R​ω\gamma+R\omega and ε​ω\varepsilon\omega with 00. Here R>0R>0 is chosen sufficiently big such that 0≤γ+R​ω+i​∂∂¯​φε0\leq\gamma+R\omega+i\partial\bar{\partial}\varphi_{\varepsilon} for all ε∈(0,1)\varepsilon\in(0,1) and φε↓φ\varphi_{\varepsilon}\downarrow\varphi as ε→0+\varepsilon\rightarrow 0^{+}. Then the previous arguments still work and statement A) rewrites as

+∞>∫X−φ(γφ+Rω)k∧Tl∧ωn−k−l≥∫X−φγφk∧Tl∧ωn−k−l≥0.+\infty>\int\limits_{X}-\varphi\,(\gamma_{\varphi}+R\omega)^{k}\wedge T^{l}\wedge\omega^{n-k-l}\geq\int\limits_{X}-\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l}\geq 0\,.

Statement B) of the theorem rewrites as

φε​(γφε+R​ω)k∧Tl⟶φ​(γφ+R​ω)k∧Tl,\displaystyle\varphi_{\varepsilon}\,(\gamma_{\varphi_{\varepsilon}}+R\omega)^{k}\wedge T^{l}\longrightarrow\varphi\,(\gamma_{\varphi}+R\omega)^{k}\wedge T^{l}\,, (3.12)
(γφε+R​ω)k+1∧Tl⟶(γφ+R​ω)k+1∧Tl,\displaystyle(\gamma_{\varphi_{\varepsilon}}+R\omega)^{k+1}\wedge T^{l}\longrightarrow(\gamma_{\varphi}+R\omega)^{k+1}\wedge T^{l}\,, (3.13)

weakly as ε→0+\varepsilon\rightarrow 0^{+} and (γφ+R​ω)k∧Tl=Tl∧(γφ+R​ω)k(\gamma_{\varphi}+R\omega)^{k}\wedge T^{l}=T^{l}\wedge(\gamma_{\varphi}+R\omega)^{k} for the relative indices (k,l)(k,l). The last inequality implies γφk∧Tl=Tl∧γφk\gamma_{\varphi}^{k}\wedge T^{l}=T^{l}\wedge\gamma_{\varphi}^{k}. In fact this follows by expanding by linearity the term (γφ+R​ω)k(\gamma_{\varphi}+R\omega)^{k} and using an induction by means of formula (3.9). The base of the induction follows from claim 2. □\Box

We consider also the subset 𝒫ˇγ:={φ∈𝒫^γ0∣∫X−φγφn<+∞}+ℝ⊂𝒫^γ\check{\cal P}_{\gamma}:=\{\varphi\in\hat{\cal P}^{0}_{\gamma}\,\mid\,\int_{X}-\varphi\,\gamma_{\varphi}^{n}<+\infty\}+\mathbb{R}\subset\hat{\cal P}_{\gamma} . Without changes in the proof of theorem 5 we get the following corollary.

Corollary 2

For all φ∈𝒫ˇγ\varphi\in\check{\cal P}_{\gamma} the assertions A)), B)) and (3.12), (3.13) of theorem 5 hold for all k=0,…,nk=0,...,n.

Let now Θ\Theta be a closed positive (n−1,n−1)(n-1,n-1)-current and consider the L2L^{2}-space

L2​(X,Θ):={α∈Γ⁡(X,Λ1,0​TX∗)∣∫Xi​α∧α¯∧Θ<+∞}/Θ−a.e,\displaystyle L^{2}(X,\Theta):=\left\{\alpha\in\Gamma(X,\Lambda^{1,0}T_{X}^{*})\;\mid\;\int\limits_{X}i\alpha\wedge\bar{\alpha}\wedge\Theta<+\infty\right\}_{\Big/\Theta-a.e}\,,

equipped with the hermitian product ⟨α,β⟩Θ:=∫Xi​α∧β¯∧Θ\left<\alpha,\beta\right>_{\Theta}:=\int_{X}i\alpha\wedge\bar{\beta}\wedge\Theta, which is well defined by the polarization identity. The Θ\Theta-almost everywhere equality relation is defined by : α∼β\alpha\sim\beta iff

∫Xi⁡(α−β)∧(α−β)¯∧Θ=0.\int\limits_{X}i(\alpha-\beta)\wedge\overline{(\alpha-\beta)}\wedge\Theta=0\,.

Let αk,α∈L2​(X,Θ)\alpha_{k},\,\alpha\in L^{2}(X,\Theta). We say that the sequence αk\alpha_{k} converges L2​(X,Θ)L^{2}(X,\Theta)-weakly to α\alpha if

∫Xi​α∧β¯∧Θ=limk→+∞∫Xi​αk∧β¯∧Θ,\int_{X}i\alpha\wedge\bar{\beta}\wedge\Theta=\lim_{k\rightarrow+\infty}\int_{X}i\alpha_{k}\wedge\bar{\beta}\wedge\Theta\,,

for all β∈L2​(X,Θ)\beta\in L^{2}(X,\Theta). Let φ∈𝒫γ0\varphi\in{\cal P}^{0}_{\gamma} such that ∫X−φΘ∧ω<+∞\int_{X}-\varphi\,\Theta\wedge\,\omega<+\infty. Then one can define ∂φ∧Θ:=∂(φ​Θ)\partial\varphi\wedge\Theta:=\partial(\varphi\Theta). We write ∂φ∈L2​(X,Θ)\partial\varphi\in L^{2}(X,\Theta) if there exists α∈L2​(X,Θ)\alpha\in L^{2}(X,\Theta) such that ∂(φ​Θ)=α∧Θ\partial(\varphi\Theta)=\alpha\wedge\Theta in the sense of currents. In this case we write

∫Xi​∂φ∧∂¯​φ∧Θ:=∫Xi​α∧α¯∧Θ.\int\limits_{X}i\partial\varphi\wedge\bar{\partial}\varphi\wedge\Theta:=\int\limits_{X}i\alpha\wedge\bar{\alpha}\wedge\Theta\,.

With this notations we have the following corolary of theorem 5.

Corollary 3

. Let (X,ω)(X,\omega) be a polarized compact Kähler manifold of complex dimension nn and let γ\gamma, TT be closed positive (1,1)(1,1)-currents with continuous local potentials, let Θ\Theta be a closed positive (n−1,n−1)(n-1,n-1)-current and consider φ∈𝒫ˇγ\varphi\in\check{\cal P}_{\gamma}, φ≤0\varphi\leq 0, ψ∈𝒫γ∩C0​(X)\psi\in{\cal P}_{\gamma}\cap C^{0}(X), ψ≤0\psi\leq 0. Then for all k,l≥0k,l\geq 0, k+l≤n−1k+l\leq n-1,

∫Xi​∂φ∧∂¯​φ∧γφk∧Tl∧ωn−k−l−1<+∞,\displaystyle\int\limits_{X}i\partial\varphi\wedge\bar{\partial}\varphi\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}<+\infty\,, (3.14)
∫Xi​∂ψ∧∂¯​ψ∧Θ<+∞.\displaystyle\int\limits_{X}i\partial\psi\wedge\bar{\partial}\psi\wedge\Theta<+\infty\,. (3.15)

Moreover let (φε)ε>0(\varphi_{\varepsilon})_{\varepsilon>0}, (ψε)ε>0⊂C∞​(X)(\psi_{\varepsilon})_{\varepsilon>0}\subset C^{\infty}(X), φε∈𝒫γ+R​ω\varphi_{\varepsilon}\in{\cal P}_{\gamma+R\omega}, ψε∈𝒫γ+ε​ω\psi_{\varepsilon}\in{\cal P}_{\gamma+\varepsilon\omega} such that φε↓φ\varphi_{\varepsilon}\downarrow\varphi, ψε↓ψ\psi_{\varepsilon}\downarrow\psi as ε→0+\varepsilon\rightarrow 0^{+}. Then

limε→0+∫Xi​∂(φε−φ)∧∂¯​(φε−φ)∧γφk∧Tl∧ωn−k−l−1=0,\displaystyle\lim_{\varepsilon\rightarrow 0^{+}}\,\int\limits_{X}i\partial(\varphi_{\varepsilon}-\varphi)\wedge\bar{\partial}(\varphi_{\varepsilon}-\varphi)\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}=0\,, (3.16)
limε→0+∫Xi​∂(ψε−ψ)∧∂¯​(ψε−ψ)∧Θ=0.\displaystyle\lim_{\varepsilon\rightarrow 0^{+}}\,\int\limits_{X}i\partial(\psi_{\varepsilon}-\psi)\wedge\bar{\partial}(\psi_{\varepsilon}-\psi)\wedge\Theta=0\,. (3.17)

Proof. By integrating by parts we obtain

∫Xi​∂φε∧∂¯​φε∧γφk∧Tl∧ωn−k−l−1\displaystyle\int\limits_{X}i\partial\varphi_{\varepsilon}\wedge\bar{\partial}\varphi_{\varepsilon}\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}
=\displaystyle= −∫Xφεi∂∂¯φε∧γφk∧Tl∧ωn−k−l−1\displaystyle-\int\limits_{X}\varphi_{\varepsilon}\,i\partial\bar{\partial}\varphi_{\varepsilon}\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}
=\displaystyle= ∫Xφε​(γ+R​ω)∧γφk∧Tl∧ωn−k−l−1\displaystyle\int\limits_{X}\varphi_{\varepsilon}\,(\gamma+R\omega)\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}
−\displaystyle- ∫Xφε​(γφε+R​ω)∧γφk∧Tl∧ωn−k−l−1.\displaystyle\int\limits_{X}\varphi_{\varepsilon}\,(\gamma_{\varphi_{\varepsilon}}+R\omega)\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}\,.

By the proof of theorem 5 we can take the limit, so

0\displaystyle 0 ≤\displaystyle\leq limε→0+∫Xi​∂φε∧∂¯​φε∧γφk∧Tl∧ωn−k−l−1\displaystyle\lim_{\varepsilon\rightarrow 0^{+}}\,\int\limits_{X}i\partial\varphi_{\varepsilon}\wedge\bar{\partial}\varphi_{\varepsilon}\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1} (3.18)
=\displaystyle= ∫Xφ⁡(γ−γφ)∧γφk∧Tl∧ωn−k−l−1<+∞.\displaystyle\int\limits_{X}\varphi\,(\gamma-\gamma_{\varphi})\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}<+\infty\,.

On the other hand the weak convergence of the sequence

φε​γφk∧Tl∧ωn−k−l−1⟶φ​γφk∧Tl∧ωn−k−l−1,\varphi_{\varepsilon}\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}\longrightarrow\varphi\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}\,,

combined with the weak continuity of the ∂\partial operator implies

∂φε∧γφk∧Tl∧ωn−k−l−1⟶∂φ∧γφk∧Tl∧ωn−k−l−1,\partial\varphi_{\varepsilon}\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}\longrightarrow\partial\varphi\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}\,,

weakly as ε→0+\varepsilon\rightarrow 0^{+}. Then the L2​(X,γφk∧Tl∧ωn−k−l−1)L^{2}(X,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1})-weak compactness implies (3.14) and the L2​(X,γφk∧Tl∧ωn−k−l−1)L^{2}(X,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1})-weak convergence ∂φε→∂φ\partial\varphi_{\varepsilon}\rightarrow\partial\varphi as ε→0+\varepsilon\rightarrow 0^{+}, which implies

∫Xi​∂φ∧∂¯​φ∧γφk∧Tl∧ωn−k−l−1\displaystyle\int\limits_{X}i\partial\varphi\wedge\bar{\partial}\varphi\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}
=\displaystyle= limε→0+∫Xi​∂φε∧∂¯​φ∧γφk∧Tl∧ωn−k−l−1\displaystyle\lim_{\varepsilon\rightarrow 0^{+}}\,\int\limits_{X}i\partial\varphi_{\varepsilon}\wedge\bar{\partial}\varphi\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}
=\displaystyle= limε→0+∫X−φεi∂∂¯φ∧γφk∧Tl∧ωn−k−l−1\displaystyle\lim_{\varepsilon\rightarrow 0^{+}}\,\int\limits_{X}-\varphi_{\varepsilon}\,i\partial\bar{\partial}\varphi\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}
=\displaystyle= limε→0+∫X−φε(γ−γφ)∧γφk∧Tl∧ωn−k−l−1\displaystyle\lim_{\varepsilon\rightarrow 0^{+}}\,\int\limits_{X}-\varphi_{\varepsilon}\,(\gamma-\gamma_{\varphi})\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}
=\displaystyle= ∫X−φ(γ−γφ)∧γφk∧Tl∧ωn−k−l−1\displaystyle\int\limits_{X}-\varphi\,(\gamma-\gamma_{\varphi})\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}
=\displaystyle= limε→0+∫Xi​∂φε∧∂¯​φε∧γφk∧Tl∧ωn−k−l−1,\displaystyle\lim_{\varepsilon\rightarrow 0^{+}}\,\int\limits_{X}i\partial\varphi_{\varepsilon}\wedge\bar{\partial}\varphi_{\varepsilon}\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}\,,

by identity (3.18). This implies (3.16) by elementary facts about Hilbert spaces. The proof of (3.15) and (3.17) is quite similar. □\Box

The conclusion of the corollary 3 still holds true if we replace the current γφk∧Tl∧ωn−k−l−1\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1} with a sum of currents

Ξ:=∑k+l≤n−1Ck,l​γφk∧Tl∧ωn−k−l−1,\Xi:=\sum_{k+l\leq n-1}C_{k,l}\,\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}\,,

where Ck,l∈ℝC_{k,l}\in\mathbb{R} such that Ξ≥0\Xi\geq 0. We infer the linearity formula

∫Xi​∂φ∧∂¯​φ∧Ξ=∑k+l≤n−1Ck,l​∫Xi​∂φ∧∂¯​φ∧γφk∧Tl∧ωn−k−l−1.\int\limits_{X}i\partial\varphi\wedge\bar{\partial}\varphi\wedge\Xi\;=\;\sum_{k+l\leq n-1}C_{k,l}\,\int\limits_{X}i\partial\varphi\wedge\bar{\partial}\varphi\wedge\gamma_{\varphi}^{k}\wedge T^{l}\wedge\omega^{n-k-l-1}\,.

Original mathematics by the credited authors. Source-backed reader collection; mathematical self-containment is not assessed.