geometry-topology / Scalar curvature; Urysohn width and macroscopic dimension
Gromov's codimension-two Urysohn width conjecture for positive scalar curvature, with the macroscopic dimension conjecture for universal covers
Principal manuscript, Theorem 1.1: for every n≥4 there is Cn such that every connected complete boundaryless Riemannian n-manifold with Scal≥1 admits a continuous map to a simplicial complex of dimension at most n−2 whose entire fibers have diameter at most Cn; no orientability, spin, compactness or bounded-geometry assumption. Corollaries: Gromov's filling-radius bound FillRad≤Cn/(2σ) for closed manifolds with Scal≥σ2, dimmc≤n−2 for universal covers of closed positive-scalar-curvature manifolds in every n≥2, and an independent proof that closed aspherical manifolds of dimension ≥4 carry no positive scalar curvature. The October 5 companions extend the width bound to the spectral condition −4Δ+Scal≥1 (n≥4, and n=3 with a graph target and bound 500/λ). Not shown: the Lipschitz form dimMC, or any explicit constant.
Principal manuscript, Theorem 1.1: for every n≥4 there is Cn such that every connected complete boundaryless Riemannian n-manifold with Scal≥1 admits a continuous map to a simplicial complex of dimension at most n−2 whose entire fibers have diameter at most Cn; no orientability, spin, compactness or bounded-geometry assumption. Corollaries: Gromov's filling-radius bound…
Principal manuscript, Theorem 1.1: for every n≥4 there is Cn such that every connected complete boundaryless Riemannian n-manifold with Scal≥1 admits a continuous map to a simplicial complex of dimension at most n−2 whose entire fibers have diameter at most Cn; no orientability, spin, compactness or bounded-geometry assumption. Corollaries: Gromov's filling-radius bound FillRad≤Cn/(2σ) for closed manifolds with Scal≥σ2, dimmc≤n−2 for universal covers of closed positive-scalar-curvature manifolds in every n≥2, and an independent proof that closed aspherical manifolds of dimension ≥4 carry no positive scalar curvature. The October 5 companions extend the width bound to the spectral condition −4Δ+Scal≥1 (n≥4, and n=3 with a graph target and bound 500/λ). Not shown: the Lipschitz form dimMC, or any explicit constant.
Principal manuscript, Theorem 1.1: for every n≥4 there is Cn such that every connected complete boundaryless Riemannian n-manifold with Scal≥1 admits a continuous map to a simplicial complex of dimension at most n−2 whose entire fibers have diameter at most Cn; no orientability, spin, compactness or bounded-geometry assumption. Corollaries: Gromov's filling-radius bound FillRad≤Cn/(2σ) for closed manifolds with Scal≥σ2, dimmc≤n−2 for universal covers of closed positive-scalar-curvature manifolds in every n≥2, and an independent proof that closed aspherical manifolds of dimension ≥4 carry no positive scalar curvature. The October 5 companions extend the width bound to the spectral condition −4Δ+Scal≥1 (n≥4, and n=3 with a graph target and bound 500/λ). Not shown: the Lipschitz form dimMC, or any explicit constant.