geometry-topology / Kahler geometry; several complex variables

Yau's question on bounded holomorphic functions: does a complete simply connected Kahler manifold with sectional curvature at most −a2<0-a^2<0 carry a nonconstant bounded holomorphic function?

Theorem 1.1: for some finite m≥2m\ge2 there is a domain T⊂Cm\mathcal T\subset\mathbb C^m, diffeomorphic to R2m\mathbb R^{2m}, with a complete Kahler metric gg satisfying Secg≤−1\mathrm{Sec}_g\le -1 and H∞(T)=CH^\infty(\mathcal T)=\mathbb C: every bounded holomorphic function is constant, so the Caratheodory pseudometric vanishes. This disproves the universal assertion in the one-sided question, and also answers Wu's 1967 bounded-domain question negatively under its hypotheses. The sectional curvatures are unbounded below, so the question under a two-sided bound −b2≤Sec≤−a2-b^2\le\mathrm{Sec}\le -a^2 remains open; the dimension is large and not made explicit.

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geometry-topologySep 25, 2026Significance 33/100Registry: unreviewed

Yau's question on bounded holomorphic functions: does a complete simply connected Kahler manifold with sectional curvature at most −a2<0-a^2<0 carry a nonconstant bounded holomorphic function?

Prior state unknown→disproved

Theorem 1.1: for some finite m≥2m\ge2 there is a domain T⊂Cm\mathcal T\subset\mathbb C^m, diffeomorphic to R2m\mathbb R^{2m}, with a complete Kahler metric gg satisfying Secg≤−1\mathrm{Sec}_g\le -1 and H∞(T)=CH^\infty(\mathcal T)=\mathbb C: every bounded holomorphic function is constant, so the Caratheodory pseudometric vanishes. This disproves the universal assertion in the one-sided question, and also answers Wu's 1967 bounded…

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Theorem 1.1: for some finite m≥2m\ge2 there is a domain T⊂Cm\mathcal T\subset\mathbb C^m, diffeomorphic to R2m\mathbb R^{2m}, with a complete Kahler metric gg satisfying Secg≤−1\mathrm{Sec}_g\le -1 and H∞(T)=CH^\infty(\mathcal T)=\mathbb C: every bounded holomorphic function is constant, so the Caratheodory pseudometric vanishes. This disproves the universal assertion in the one-sided question, and also answers Wu's 1967 bounded-domain question negatively under its hypotheses. The sectional curvatures are unbounded below, so the question under a two-sided bound −b2≤Sec≤−a2-b^2\le\mathrm{Sec}\le -a^2 remains open; the dimension is large and not made explicit.

Theorem 1.1: for some finite m≥2m\ge2 there is a domain T⊂Cm\mathcal T\subset\mathbb C^m, diffeomorphic to R2m\mathbb R^{2m}, with a complete Kahler metric gg satisfying Secg≤−1\mathrm{Sec}_g\le -1 and H∞(T)=CH^\infty(\mathcal T)=\mathbb C: every bounded holomorphic function is constant, so the Caratheodory pseudometric vanishes. This disproves the universal assertion in the one-sided question, and also answers Wu's 1967 bounded-domain question negatively under its hypotheses. The sectional curvatures are unbounded below, so the question under a two-sided bound −b2≤Sec≤−a2-b^2\le\mathrm{Sec}\le -a^2 remains open; the dimension is large and not made explicit.

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