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[#P2510] Homotopy type of a Lee-metric Rips complex on the 7 by 7 torus

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Problem. On \((\mathbb Z/7\mathbb Z)^2\), give each coordinate its circular distance and use their sum as the Lee metric. Let \(Y\) be the clique complex joining two vertices when their Lee distance is at most 2. Is \(Y\) homotopy equivalent to the 2-torus?

1Context

The complex is finite and translation-invariant. Orbitwise Morse matching can compress attempted collapses into a small collection of local cases.

2Remarks

Remark 1. The circular distance between residues a and b is \(\min(|a-b|,7-|a-b|)\).

Remark 2. The clique complex fills every complete subgraph by a simplex, so Y has simplices above dimension two.

3What counts as a solution

  • Give an explicit homotopy equivalence or a certified collapse to a torus triangulation, or compute an invariant that differs from that of the 2-torus.

1The answerSupportednot Lean-verified

Answer (The complex is homotopy equivalent to the 2-torus). A published torus-grid theorem applies with n = 7 and k = 2, so the answer to the candidate question is yes.[1]

Resolution argument

The candidate complex \(Y\) is exactly the closed Vietoris-Rips complex \(\operatorname{VR}(T_{7,7};2)\) in the notation of Adams, Adetowubo, Barriga-Acosta, Feng, and Sterling. Their metric on \(T_{n,n}\) is the sum of the two circular coordinate distances, and a finite set is a simplex when its diameter is at most the scale. This agrees with the stated Lee metric and clique convention.

Theorem 5.8 of the paper proves \[ \operatorname{VR}(T_{n,n};k)\simeq T^2 \qquad\text{for }k\geq2\text{ and }n>3k. \] Here \(k=2\) and \(n=7>6=3k\). Therefore \[ \boxed{Y\simeq T^2}. \]

The proof classifies the facets in the small-scale range and realizes their complex as the nerve of a good cover of \(\mathbb R^2/(7\mathbb Z)^2\) by projected \(l^1\)-balls. Every nonempty finite intersection in the cover is contractible, so the nerve theorem gives the homotopy equivalence. A simplicial collapse is unnecessary because the published nerve equivalence settles the stated question.

1Records

4 records

Notes and companion materialContext, examples, and computations

Original intake status. SOLVED in the independently reviewed TheoremDB packet as of 2026-08-01. A published torus-grid theorem applies with n = 7 and k = 2, so the answer to the candidate question is yes.

  • The current primary paper was checked at n=7 and k=2. Its small-scale theorem applies because 2 <= (7-1)/3 and proves the requested torus homotopy type. The optional SymPy homology replay was unavailable because SymPy is absent from this checkout; the published proof covers the full acceptance condition.
  • Fresh exact-title, parameter, primary-source, and controlled-corpus searches were completed on 2026-08-01.

Computational notes

  • Exact clique enumeration produced 49 vertices, 294 edges, 490 triangles, 294 tetrahedra, and 49 four-simplices. Its ordinary Euler characteristic is 0, matching the torus. For side lengths 8 and 9 with the same radius, the exact face vectors are [1,64,384,640,384,64] and [1,81,486,810,486,81], including the empty face in the initial entry.
How the 4 records connectTyped relations and evidence flow
How the records connect to the problem

ProblemHomotopy type of a Lee-metric Rips complex on the 7 by 7 torus

2See also

How to cite

TheoremDB contributors, “Homotopy type of a Lee-metric Rips complex on the 7 by 7 torus,” TheoremDB research memory, snapshot of July 24, 2026. https://theoremdb.org/statements/lee-rips-torus-7-homotopy

This problem includes 4 records joined by 3 typed links, sourced from doi.org[1], current as of July 24, 2026.

1Lean verification

Lean formalization needed

An informal proof is recorded. A Lean formalization still needs to be attached. TheoremDB Researcher can start from the exact statement and pinned world.

Open TheoremDB Researcher

The prefilled request prepares the target and checks drafts. It submits the accepted proof and polls verification through any packet-review handoff.

1References

  1. Packet source. Henry Adams, Adenike Yeside Adetowubo, Hector Barriga-Acosta, Ziqin Feng, and John Sterling, “Vietoris–Rips Complexes of Torus Grids”. Mediterranean Journal of Mathematics 22(7) (2025), 173. DOI 10.1007/s00009-025-02945-9. Integral computation in lee7-artifact-exact-cliques-and-smith; comparison with Adams et al., Theorem 5.8. open copy ↗preprint · primary source · arXiv:2502.07134v2, version checked 2026-08-01 · checked 2026-08-01Source use: original summary.This source fixes the published convention, theorem, formula, or independent answer used to check the packet resolution.Also cited at Adams et al., Vietoris-Rips Complexes of Torus Grids, Mediterranean Journal of Mathematics 22, 173 (2025), DOI 10.1007/s00009-025-02945-9, abstract and Theorem 5.8 on page 14; John Sterling, Vietoris-Rips Complexes of Torus Grids, Auburn University master's thesis, 2025, abstract and Theorem 4.2 on pages 26-27.Also cited at Henry Adams, Adenike Yeside Adetowubo, Hector Barriga-Acosta, Ziqin Feng, and John Sterling, Vietoris-Rips Complexes of Torus Grids, Mediterranean Journal of Mathematics 22, article 173 (2025), Sections 2.1 and 2.3 for the metric and closed Rips convention, Theorem 5.8 on page 14; arXiv:2502.07134v2.Also cited at Inline Python and SymPy computation executed on 2026-07-24 with SymPy 1.14.0.For Homotopy type of a Lee-metric Rips complex on the 7 by 7 torus, the reviewed source scope is Adams et al., Vietoris-Rips Complexes of Torus Grids, Mediterranean Journal of Mathematics 22, 173 (2025), DOI 10.1007/s00009-025-02945-9, abstract and Theorem 5.8 on page 14; John Sterling, Vietoris-Rips Complexes of Torus Grids, Auburn University master's thesis, 2025, abstract and Theorem 4.2 on pages 26-27. The packet makes no inference beyond that cited scope.Source named by the research packet.
  2. John Sterling, Vietoris-Rips Complexes of Torus Grids, master’s thesis, Auburn University, 2025. Thesis discussion relevant to Homotopy type of a Lee-metric Rips complex on the 7 by 7 torus. scholarly publication · reference source · checked 2026-08-01Source use: citation only.For Homotopy type of a Lee-metric Rips complex on the 7 by 7 torus, the reviewed source scope is Thesis discussion relevant to Homotopy type of a Lee-metric Rips complex on the 7 by 7 torus.. The packet makes no inference beyond that cited scope.

Original finite Rips-complex target on an explicit 49-point metric space.

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