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2.2 Uniform domination by capacity [02GB]

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2.2 Uniform domination by capacity

We now show that the measure μt:=ft​ωtn/V​o​lωt\mu_{t}:=f_{t}\omega_{t}^{n}/\penalty Vol_{\omega_{t}} are uniformly strongly dominated by the normalized capacity Capωt/V​o​lωt​(X).\mathrm{Cap}_{\omega_{t}}/\penalty Vol_{\omega_{t}}(X). It actually follows from a carefull reading of the no parameter proof given in [EGZ], [BGZ].

Lemma 2.2

There exists a constant C0=C0​(π,‖F‖Lp​(ωXn))>0C_{0}=C_{0}(\pi,\|F\|_{L^{p}(\omega_{X}^{n})})>0 such that for any compact set K⊂XK\subset X and t∈]0,1]t\in]0,1],

μt​(K)≤C0n​(Capωt​(K)V​o​lωt​(X))2.\mu_{t}(K)\leq C_{0}^{n}\left(\frac{\mathrm{Cap}_{\omega_{t}}(K)}{Vol_{\omega_{t}}(X)}\right)^{2}.

Proof: Fix a compact set K⊂XK\subset X. Set Vt:=V​o​lωt​(X)V_{t}:=Vol_{\omega_{t}}(X). Hölder’s inequality yields

μt​(K)≤(∫Xftp′​ωtnVt)1/p′​(∫KωtnVt)1/q′.\mu_{t}(K)\leq\left(\int_{X}f_{t}^{p^{\prime}}\frac{\omega_{t}^{n}}{V_{t}}\right)^{1/\penalty p^{\prime}}\left(\int_{K}\frac{\omega_{t}^{n}}{V_{t}}\right)^{1/\penalty q^{\prime}}.

It remains to dominate uniformly the normalized volume forms ωtn/Vt\omega_{t}^{n}/\penalty V_{t} by the normalized capacities Capωt/Vt\mathrm{Cap}_{\omega_{t}}/\penalty V_{t}. Fix σ>0\sigma>0 and observe that for any t∈]0,1]t\in]0,1],

∫KωtnVt≤∫Xe−σ⁡(VK,ωt−maxX⁡VK,ωt)​ωtnVt​Tωt​(K)σ,\int_{K}\frac{\omega_{t}^{n}}{V_{t}}\leq\int_{X}e^{-\sigma(V_{K,\omega_{t}}-\max_{X}V_{K,\omega_{t}})}\frac{\omega_{t}^{n}}{V_{t}}T_{\omega_{t}}(K)^{\sigma},

where

VK,ωt:=sup{ψ∈P​S​H​(X,ωt);ψ≤0,on​K}V_{K,\omega_{t}}:=\sup\{\psi\in PSH(X,\omega_{t});\psi\leq 0,\ \mathrm{on}\ K\}

is the ωt−\omega_{t}-extremal function of KK and Tωt(K):=exp(−supXVK,ωt)T_{\omega_{t}}(K):=\exp(-\sup_{X}V_{K,\omega_{t}}) is the associated ωt−\omega_{t}-capacity of KK (see [GZ 1] for their properties).

Observe that ωtn/Vt≤c1​ω1n\omega_{t}^{n}/\penalty V_{t}\leq c_{1}\omega_{1}^{n} and ωt≤ω1\omega_{t}\leq\omega_{1}, hence the family of functions VK,ωt−maxX⁡VK,ωtV_{K,\omega_{t}}-\max_{X}V_{K,\omega_{t}} is a normalized family of ω1−\omega_{1}-psh functions. Thus there exists σ>0\sigma>0 which depends only on (X,ω1)(X,\omega_{1}) and a constant B=B⁡(σ,X,ω1)B=B(\sigma,X,\omega_{1}) such that ([Z])

∫Xe−σ⁡(VK,ωt−maxX⁡VK,ωt)ωtnVt≤B,∀t∈]0,1].\int_{X}e^{-\sigma(V_{K,\omega_{t}}-\max_{X}V_{K,\omega_{t}})}\frac{\omega_{t}^{n}}{V_{t}}\leq B,\forall t\in]0,1].

The Alexander-Taylor comparison theorem (see Theorem 7.1 in [GZ 1]) now yields for a constant C3=C3​(π,‖F‖Lp​(X))C_{3}=C_{3}(\pi,\|F\|_{L^{p}(X)})

μt(K)≤C3exp[−σ(VtCapωt​(K))1/n],∀t∈]0,1].\mu_{t}(K)\leq C_{3}\exp\left[-\sigma\left(\frac{V_{t}}{\mathrm{Cap}_{\omega_{t}}(K)}\right)^{1/\penalty n}\right],\forall t\in]0,1].

We infer that there is a constant C4=C4​(π,‖F‖Lp​(X))C_{4}=C_{4}(\pi,\|F\|_{L^{p}(X)}) such that

(2) μt(K)≤C4(Capωt​(K)Vt)2,∀t∈]0,1].\mu_{t}(K)\leq C_{4}\left(\frac{\mathrm{Cap}_{\omega_{t}}(K)}{V_{t}}\right)^{2},\forall t\in]0,1].

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