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Plurisubharmonic functions [02EV]

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Plurisubharmonic functions

Let VV be a normal analytic space of pure dimension nn. A plurisubharmonic (psh) function φ\varphi on VV is an upper semicontinuous function on VV with values in ℝ∪{−∞}\mathbb{R}\cup\{-\infty\}, which is not locally −∞-\infty, and extends to a psh function in some local embedding V→ℂNV\to\mathbb{C}^{N}. The function φ\varphi is strongly psh (resp. 𝒞0{\mathcal{C}}^{0}, resp. 𝒞∞{\mathcal{C}}^{\infty}) iff it extends to a strongly psh function (resp. 𝒞0{\mathcal{C}}^{0}, resp. 𝒞∞{\mathcal{C}}^{\infty}) in some local embedding. A continuous function is psh iff its restriction to Vr​e​gV^{reg} is so [FN]. A bounded psh function on Vr​e​gV^{reg} extends to VV.

A pluriharmonic function on VV is a real valued continuous function on VV ff on VV such that one of the following equivalent conditions holds:

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    ff is locally the real part of a holomorphic function.

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    Given a local embedding V→ℂNV\to\mathbb{C}^{N}, ff extends locally to a pluriharmonic function on ℂN\mathbb{C}^{N}.

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    f|Vr​e​gf|_{V^{reg}} is pluriharmonic.

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