Positive biorthogonal curvature on $S^2\times T^2$

Zhiqi Chen; Hui Zhang

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arXiv · 2609.08119

Positive biorthogonal curvature on $S^2\times T^2$

Zhiqi Chen·Hui Zhang

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Abstract

We construct explicit Riemannian metrics with positive biorthogonal curvature on $S^2\times T^2$, answering a question of Bettiol. In particular, positive biorthogonal curvature on a closed four-manifold does not force its fundamental group to be virtually free.

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Zhiqi Chen, Hui Zhang. 2026-09-08. Positive biorthogonal curvature on $S^2\times T^2$. https://arxiv.org/abs/2609.08119

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