Semipositivity conjecture for divisors with topologically trivial normal bundle

Let XX be a complex surface and let YY be a compact smooth curve holomorphically embedded in XX such that its normal bundle is topologically trivial. Let [Y][Y] denote the line bundle on XX corresponding to the divisor YY, and let a pair (Y,X)(Y,X) be of type (β)(\beta) in the sense used in the paper.

Semipositivity conjecture. The line bundle [Y][Y] admits a CC^\infty Hermitian metric with semi-positive curvature if and only if the pair (Y,X)(Y,X) is of type (β)(\beta).

The conjecture is motivated by the preceding corollary, which proves this equivalence under the additional hypotheses imposed there. The general claim concerns complex surfaces containing compact curves with topologically trivial normal bundle.

Sources & referencesView supporting material

Primary source

Takayuki Koike and Noboru Ogawa, “On the neighborhood of a torus leaf and dynamics of holomorphic foliations”, arXiv:1808.10219 (2025).

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