Gromov's noncompact injectivity radius conjecture

From papers

Let (Mn,g)(M^n,g) be a complete, non-compact Riemannian manifold with uniformly positive scalar curvature

Sc(g)(n1)(n2).\operatorname{Sc}(g)\geq (n-1)(n-2).

Gromov's noncompact injectivity radius conjecture. Then

Inj(M)π,\operatorname{Inj}(M)\leq \pi,

and equality holds if and only if MM is isometric to

(Sn1(1)×R,gSn1+dt2).(\mathbb S^{n-1}(1)\times\mathbb R, g_{\mathbb S^{n-1}}+dt^2).

The source notes that even the weaker bound Inj(M)π\operatorname{Inj}(M)\leq\pi is open for complete noncompact manifolds with uniformly positive scalar curvature. The conjecture is presented as a stronger rigidity statement.

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Sources & referencesView supporting material

Primary source

Jinmin Wang, Zhizhang Xie, Guoliang Yu and Bo Zhu, “Filling Radius, Quantitative K-theory and Positive Scalar Curvature”, arXiv:2311.15347 (2024).

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