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Alpöge–Claude reports: a complex structure on the six-sphere

The Alpöge–Claude manuscript claims a compact complex threefold, obtained by completing a modular family of complex two-tori, whose underlying smooth manifold is diffeomorphic to S⁶.

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Alpöge–Claude reports: a complex structure on the six-sphere

The Alpöge–Claude manuscript claims a compact complex threefold, obtained by completing a modular family of complex two-tori, whose underlying smooth manifold is diffeomorphic to S⁶. Philip Engel supplies a separate geometric exposition and self-contained proof of the construction.

Read original source Original Alpöge–Claude constructionalpo.ge

Original report: 2026-08-23

Understanding the problem

Read the background

The Alpöge–Claude manuscript claims a compact complex threefold, obtained by completing a modular family of complex two-tori, whose underlying smooth manifold is diffeomorphic to S⁶. Philip Engel supplies a separate geometric exposition and self-contained proof of the construction.

The six-sphere admits an almost complex structure, but the longstanding Hopf problem asks whether it admits an integrable complex structure. An almost complex structure alone does not answer that question.

Why it matters

If correct, resolves the longstanding complex-structure existence problem for the six-sphere and provides a construction with further geometric research directions.

What counts as progress

A sourced advance or substantial formalization with the exact target, hypotheses, baseline and AI role stated. Importance and verification are assessed separately.

What to watch for

  • Compare the precise hypotheses and baseline; retain human and prior-work attribution.
  • Preprint claim; broad proof acceptance is not assessed. Engel’s exposition supports mathematical understanding but is not a AIProofWatch proof audit. The precise Alpöge–Claude interaction is not fully documented in Engel’s account. AIProofWatch has not checked either full argument or compiled a formalization.

Background review: 2026-10-11. Selected sources:

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