Kobayashi's conjecture on fundamental groups of positively curved semi-Riemannian manifolds

Let nn and qq be positive integers with n2qn \geq 2q. Let (M,g)(M,g) be an nn-dimensional geodesically complete semi-Riemannian manifold of index qq, and suppose its sectional curvature has a positive lower bound. Kobayashi's conjecture. The manifold MM is never compact, and, if n3n \geq 3, its fundamental group π1(M)\pi_1(M) is finite. The conjecture is presented as a perturbative analogue of the Calabi–Markus–Wolf finiteness theorem for positive constant curvature; the supplied text also says that it is true by Kulkarni's theorem, which reduces the one-sided sectional-curvature bound to constant curvature.

Sources & referencesView supporting material

Primary source

Jun-ichi Mukuno, “On the fundamental group of semi-Riemannian manifolds with positive curvature tensor”, arXiv:1704.04944 (2021).

Additional references

2 papers in this index state this conjecture (2014–2017). The statement above is taken from the most recent of them; the others are arXiv:1409.0957.

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