The fiber-bundle conjecture for Sharafutdinov projections

Let XAlexn(0)X\in \operatorname{Alex}^n(0) be an open Alexandrov space, let SS be a compact totally convex soul without boundary, and let ϕ:XS\phi:X\to S be the Sharafutdinov projection. Write m=dim(S)1m=\dim(S)\geq 1. A point is weakly kk-strained if it admits the configuration of (k+1)(k+1) points used to define weak straining in the source, with the relevant comparison angles greater than π/2\pi/2.

Fiber-bundle conjecture. If all points in SS are weakly mm-strained, then ϕ:XS\phi:X\to S is a fiber bundle map.

The conjecture proposes sufficient regularity of the soul for the Sharafutdinov projection to be a fiber bundle. The source emphasizes that submetry alone does not imply the fiber-bundle property and does not state a resolution.

Sources & referencesView supporting material

Primary source

Xueping Li and Xiaochun Rong, “Open Alexandrov spaces of nonnegative curvature”, arXiv:2311.15174 (2025).

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