Characterization of Tangent Cones of Noncollapsed Limits with Lower Ricci Bounds and Applications

By T. Colding, A. Naber. 2011

69 citations recorded by the source corpus.

AbstractConsider a limit space $${(M_\alpha,g_\alpha,p_\alpha)\stackrel{GH}{\rightarrow} (Y,d_Y,p)}$$, where the $${M_\alpha^n}$$ have a lower Ricci curvature bound and are volume noncollapsed. The tangent cones of Y at a point $${p\in Y}$$ are known to be metric cones C(X), however they need not be unique. Let $${\overline\Omega_{Y,p}\subseteq\mathcal{M}_{GH}}$$ be the closed subset of compact metric spaces X which arise as cross sections for the tangents cones of Y at p. In this paper we study the properties of $${\overline\Omega_{Y,p}}$$. In particular, we give necessary and sufficient conditions for an open smooth family $${\Omega\equiv (X,g_s)}$$ of closed manifolds to satisfy $${\overline\Omega =\overline\Omega_{Y,p}}$$ for some limit Y and point $${p\in Y}$$ as above, where $${\overline\Omega}$$ is the closure of Ω in the set of metric spaces equipped with the Gromov–Hausdorff topology. We use this characterization to construct examples which exhibit fundamentally new behaviors. The first application is to construct limit spaces (Yn, dY, p) with n ≥ 3 such that at p there exists for every 0 ≤ k ≤ n−2 a tangent cone at p of the form , where Xn-k-1 is a smooth manifold not isometric to the standard sphere. In particular, this is the first example which shows that a stratification of a limit space Y based on the Euclidean behavior of tangent cones is not possible or even well defined. It is also the first example of a three dimensional limit space with nonunique tangent cones. The second application is to construct a limit space (Y5, dY, p), such that at p the tangent cones are not only not unique, but not homeomorphic. Specifically, some tangent cones are homeomorphic to cones over while others are homeomorphic to cones over .

Subfields: Applied Mathematics, Geometry and Topology

View Paper: https://www.semanticscholar.org/paper/ec57f0ce14497f06d8fc6d31323fa9b6d888e2c4

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Applied Mathematics

In Geometry and Topology

Citations in the corpus

Euclidean spaces as weak tangents of infinitesimally Hilbertian metric measure spaces with Ricci curvature bounded below (2013, background): “Notice however, that there can be points in the Ricci-limits where the tangent is not unique, see for instance [18] for examples.”