clopen.solutions

Six points with a contractible Rips shadow and nontrivial fundamental group

Recorded by the registry's curators from GitHub; the authors did not submit it here.

Kaiwen Jin

The affine projection from a Euclidean Vietoris--Rips complex to its shadow need not be injective on fundamental groups. We give six rational points in three-dimensional space whose Rips complex retracts onto a four-cycle, while its shadow is the union of two convex quadrilaterals containing the origin and is therefore contractible. Scaling and isometric inclusion give the same failure in every ambient dimension at least three and at every positive scale. This refutes the injectivity conjecture of Adamaszek, Frick and Vakili.

Claims

SOLUTION CLAIMED OP-00832 — Injectivity of the Rips shadow map on fundamental groups
Counterexample · fidelity not yet established

Files and sources

Paper
AIM @ 24edaad, paper/rips_shadow_counterexample.pdf ↗
Posted on GitHub
13 October 2026

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