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Open questions and potential solutions

Insights, fruitful questions and potential solutions arising from Normalisers of parabolic subgroups of Artin–Tits groups and Tits cone intersections.

2. Potentially fruitful questions

Research question 01

Let (W,S) be irreducible affine with ∣S∣≥3, let A be its Artin–Tits group, and let ∅≠J⊊S. Put G=N(W,J)=Norm⁡W(WJ)/WJ and M=XJC, using the article’s product-cone complement. Are the algebraic and covering extensions 1→N(P,J)→N(A,J)→G→1 and 1→π1(M)→π1(M/G)→G→1 isomorphic over the identity of G, with M/G a K(N(A,J),1)?

Why it matters

This affine specialization separates identification of the normaliser extension from the topology of the relative complement. Normalizing the affine height gives concrete smaller arrangement complements. Maximal proper parabolics provide a particularly sharp first test: their geometric model is contractible, so the conjecture requires the corresponding Artin parabolic to be self-normalising.

Originality

The question is a specialization of the authors’ Conjecture 1.10, not a new conjecture. The height normalization and low-dimensional arguments below are elementary developments using independent suppliers; no worldwide novelty is claimed. This author checked the formulation, geometric conventions and spherical comparison sections, but did not independently repeat the frozen assessor’s complete 33-page novelty assessment.

Current knowledge

Checked on 2026-11-14: the arXiv record displays v3 dated 2026-07-30, whose Theorem 1.8 assumes finite W and whose Conjecture 1.10 asks for arbitrary W. Paolini–Salvetti Theorem 8.15 establishes classical affine asphericity, corresponding to J empty. Targeted searches for the relative conjecture and affine normaliser models supplied no independently verified resolution of the entire nonempty-J family. Primary release entry 254 advertises a classical finite-rank resolution; that advertisement is status evidence only, and its manuscript is not used as a theorem here.

Potential solution

Partial solutionProposed approach

The geometric subresults below are proved: the relative complement splits as a contractible quadrant times a normalized affine arrangement complement; its higher homotopy groups vanish when ∣S∖J∣≤2. For maximal proper J, the complement is contractible and N(W,J) is trivial. These results do not identify the Artin normaliser extension. Completion of the assigned question remains proposed and unresolved.

Argument and next steps

Choose a positive radical vector delta and normalize a complex functional z by its nonzero height z(delta). This removes a contractible factor and leaves an arrangement in complex dimension |S\setminus J|-1. Dimension zero gives a point; dimension one gives a complex line with a locally finite set of real punctures. Compactness reduces every higher-sphere map in the latter space to a finitely punctured disk. For maximal J, height preservation and the independent chamber-stabilizer theorem make the Coxeter normaliser quotient trivial, reducing the conjecture to Norm_A(AJ)=AJ. A completion must construct the compatible Artin normaliser comparison rather than infer it from ordinary affine asphericity.

Proof sketch or overall strategy

First establish the affine-height normalization independently of the article’s conjectural normaliser identification. Prove the zero- and one-dimensional normalized cases, then isolate the remaining algebraic comparison. The numbered argument distinguishes proved subresults from proposed continuation. Existing source records are reproduced verbatim from the frozen inventory; current-author reading limits are stated separately in the dependencies and gaps.

Numbered argument
  1. The assigned question retains both requirements of the authors’ conjecture: compatible identification of the extensions and the classifying-space assertion. Theorem 1.8 proves these only for finite W. Paolini–Salvetti’s independently checked affine theorem concerns the ordinary orbit configuration space, so it supplies the J-empty boundary case rather than the requested relative normaliser comparison. [article-formulation, classical-affine-asphericity]
  2. For irreducible affine data, the independent positive-radical lemma supplies δ=∑sδsαs with every δs>0 and B(δ,v)=0. The reflection formula gives sδ=δ, hence every w fixes delta. Consequently the height h(f)=f(δ) is invariant under the dual W-action. [math:def-cg-irreducible-affine-coxeter-type, math:lem-cg-positive-radical-and-affine-gram-exclusions, math:def-cg-real-coxeter-form-and-reflection, math:def-cg-canonical-reflection-homomorphism, math:def-cg-dual-chambers-and-reflection-hyperplanes]
  3. Write C for the closed fundamental chamber. If f∈wC, invariance gives h(f)≥0; equality forces w−1f=0, since its simple-root coordinates are nonnegative and all delta coefficients are positive. Conversely, if h(f)>0, the point f/h(f) lies in the affine slice h=1. The independent affine realization theorem says that translates of the closed fundamental alcove cover that slice, so f belongs to U. Thus U={h>0}∪{0}. For proper J, h restricts nontrivially to EJ, and therefore IJ={f∈EJ:h(f)>0}. In particular these relative interior points are ambient interior points. [step:2, relative-model-definitions, math:def-cg-tits-cone-and-fundamental-chamber, math:thm-cg-affine-gram-classification-and-euclidean-realization]
  4. Put r=∣S∖J∣, FJ={f∈EJ:h(f)=1} and Q={a∈C:ℜa>0,ℑa>0}. Intersect each proper restricted root hyperplane with FJ, discarding empty intersections and repetitions, to obtain an affine arrangement AJ. There is a homeomorphism M≅Q×(FJ,C∖⋃AJ,C) given by z↦(h(z),z/h(z)), with inverse (a,w)↦aw. Indeed the article’s two real-cone conditions become precisely h(z) in Q, and every root equation satisfies α(z)=h(z)α(z/h(z)). The complexified affine slice has dimension r-1. [step:3, relative-model-definitions, math:def-cg-dual-chambers-and-reflection-hyperplanes]
  5. If r=1, FJ is a single point. Every proper linear hyperplane of EJ is the origin and therefore misses IJ. The normalized arrangement is empty and M is homeomorphic to Q. Straight-line contraction inside the convex set Q proves that M is contractible. [step:4, relative-model-definitions]
  6. The dual reflection formula shows that Fix⁡(WJ)=EJ: a functional is fixed by sj exactly when it vanishes on alpha_j. A normaliser of WJ consequently preserves EJ. When r=1, height preservation forces its action on this line to be the identity. Choose u in C with zero coordinates exactly J; the independent point-stabilizer theorem gives Stab⁡W(u)=WJ. Every normaliser element fixes u, so Norm⁡W(WJ)=WJ and G is trivial. Thus, for maximal proper J, the complete assigned assertion is equivalent to the still-unproved-here algebraic statement Norm⁡A(AJ)=AJ. [step:2, step:5, relative-model-definitions, math:def-cg-dual-chambers-and-reflection-hyperplanes, math:thm-cg-dual-chamber-intersections-and-point-stabilizers]
  7. If r=2, FJ is a real affine line. Its nonempty arrangement hyperplanes form a locally finite set Λ⊂R: every compact subset of FJ lies in the ambient Tits-cone interior by step 3, where the independent local-finiteness theorem bounds the ambient root hyperplanes meeting it. Hence the normalized complement is C∖Λ. Any map from a sphere of dimension at least two has bounded image and therefore lies in an open disk containing only finitely many punctures. The independently supplied finitely punctured disk lemma null-homotopes that map inside this disk. The same finite-disk argument connects any two points. Since Q contracts, πn(M)=0 for every n at least two. Together with step 5 this establishes upstairs higher-homotopy vanishing for every nonempty proper J in affine rank three. [step:3, step:4, step:5, math:thm-cg-tits-cone-interior-and-local-finiteness, math:lem-a-finitely-punctured-disk-retracts-to-a-wedge-of-circles]
  8. A nonempty-J affine example shows why no finite-CW assertion should accompany this reduction. Take type A~2 with indices 0,1,2, all off-diagonal labels 3, and J={1}. Here δ=α0+α1+α2. Direct reflection multiplication for w=s0s1s2s1 gives wα2=α2−δ and wδ=δ, so α2−nδ is a root for every integer n. In coordinates a=f(δ) and b=f(α2) on EJ, these roots give distinct restricted hyperplanes b−na=0. Thus the puncture set of step 7 contains every integer. A small meridian around each integer can avoid all other punctures by local finiteness. Under the maps ζ↦(ζ−n)/∣ζ−n∣ to the circle, these meridians have the Kronecker-delta homology evaluations. Their first-homology classes are therefore integrally independent. Hatcher’s cellular-homology result excludes a finite CW homotopy model for M. This says nothing against possible finite models downstairs. [step:4, step:7, math:def-cg-real-coxeter-form-and-reflection, math:def-cg-canonical-reflection-homomorphism, finite-cw-homology]
  9. For continuation, first settle the Artin self-normaliser test in step 6 and then compare the geometric extension with the Artin normaliser extension when r=2. The spherical proof cannot simply be transplanted: for maximal proper J, adjoining its missing generator gives the infinite group W, so the spherical formula involving the longest positive lift for J plus that generator is unavailable. For r=2, elementary one-generator enlargements are spherical, but adjoining both missing generators again gives all of S. An applicable normaliser-generation and relation theorem, with the required extension compatibility, remains to be proved or independently sourced. [step:6, step:7, article-formulation, math:lem-cg-positive-radical-and-affine-gram-exclusions]
  10. The general affine question remains open in this account: step 7 proves only a low-dimensional upstairs topological requirement, and step 9 is a research programme. Ordinary affine asphericity supplies neither the missing normaliser map nor its inverse. Likewise the primary release advertisement is not a verified relative theorem. No conclusion about the full family is inferred from either source. [step:1, step:7, step:9, classical-affine-asphericity, release-status]
Immediate dependencies
  • article-formulation: Theorem 1.8 identifies the algebraic and geometric extensions and supplies the classifying-space conclusion for finite W. Conjecture 1.10 asks for the same statement for arbitrary Coxeter groups. Sections 5–6 explicitly impose spherical type. Source: https://arxiv.org/abs/2509.21915; Frozen v3: equations (1.2), (1.5)–(1.7), Theorem 1.8, pp.1–3; Conjecture 1.10, p.4; §§5–6, pp.21–27.. Reading limits: Current author read the introductory formulation and extracted §§5–6, inspected rendered pp.3–7, and checked the relevant spherical definitions and comparison arguments. This is attribution and proof-method context, never an independent proof of the conjecture. The inventory’s complete-article reading record belongs to the frozen assessment and is not claimed as this author’s reading.
  • relative-model-definitions: Use the standard Artin presentation, with alternating length-m braid relations for finite labels; AJ is the subgroup generated by its J-generators, pi sends each Artin generator to its Coxeter generator, and P=ker(pi). Define N(A,J)=Norm_A(AJ)/AJ, G=Norm_W(WJ)/WJ, and N(P,J) as the image of P intersect Norm_A(AJ). With U the Tits cone, set EJ={f:f(alpha_j)=0 for j in J}, IJ=int_EJ(U intersect EJ), and M=(IJ+i IJ) minus the complexified proper restricted root hyperplanes. A comparison of extensions must commute with the displayed arrows and induce the identity on G. Source: self-contained; Conventions used in steps 1–10; geometric definitions agree with original equations (3.1), (3.3), (3.26), verified on PDF pp.7 and 13.. Reading limits: These are explicit definitions, not imported normaliser or asphericity results. In particular, surjectivity of the normaliser map and the desired extension isomorphism are not inferred merely from the presentation.
  • math:def-cg-real-coxeter-form-and-reflection: For finite S the canonical Coxeter form has diagonal entries 1, off-diagonal entries minus cos(pi/m), and entry -1 for infinite labels. Its simple reflection is rs(v)=v-2B(v,alpha_s)alpha_s; the form may be degenerate. Source: math:def-cg-real-coxeter-form-and-reflection; Definition, clauses (2)–(3).. Reading limits: Read the complete supplied item and metadata. Use its mathematical definition under the stated finite-rank hypotheses; no audit of its cited literature is claimed.
  • math:def-cg-canonical-reflection-homomorphism: The canonical representation sends s to rs, and its roots are rho(w)alpha_s for w in W and s in S. Source: math:def-cg-canonical-reflection-homomorphism; Definition, clauses (1)–(2).. Reading limits: Read the complete supplied definition and metadata. Its representation and root interfaces are used; no new proof or publication acceptance is asserted.
  • math:def-cg-dual-chambers-and-reflection-hyperplanes: The dual action is (wf)(v)=f(w−1v), the closed chamber has nonnegative simple-root coordinates, CJ has zero coordinates exactly J, and Halpha is the kernel of evaluation on alpha. These definitions apply to degenerate forms. Source: math:def-cg-dual-chambers-and-reflection-hyperplanes; Definition, clauses (1)–(2).. Reading limits: Read the complete supplied item and metadata, including its explicit degenerate-form convention.
  • math:def-cg-tits-cone-and-fundamental-chamber: For the finite-rank canonical representation, U is the union of wC over W, with C the closed fundamental chamber. Source: math:def-cg-tits-cone-and-fundamental-chamber; Definition, clauses (1)–(2).. Reading limits: Read the definition and metadata. The closed-chamber convention was separately checked against the rendered original PDF p.5.
  • math:def-cg-irreducible-affine-coxeter-type: Irreducible affine form type means that the Coxeter diagram is connected and its canonical form is positive semidefinite of corank one. This excludes merely infinite systems with indefinite form. Source: math:def-cg-irreducible-affine-coxeter-type; Definition, clause (1), with conventions in clause (5).. Reading limits: Read the complete definition, remarks and metadata. The equivalence with the usual affine realization is supplied by the separately listed classification theorem.
  • math:lem-cg-positive-radical-and-affine-gram-exclusions: For a connected positive-semidefinite singular Coxeter form, its radical is spanned by a vector with every simple-root coefficient positive, and every proper principal submatrix is positive definite; every proper standard parabolic is finite. Source: math:lem-cg-positive-radical-and-affine-gram-exclusions; Statement (1)–(2); proof steps 1.1–3.2 and 4.1.. Reading limits: Read the complete supplied lemma and its local proof. Only the positive-radical and proper-parabolic clauses are used; no prerequisite-source defect audit was undertaken.
  • math:thm-cg-affine-gram-classification-and-euclidean-realization: For connected affine canonical Coxeter data, the slice f(delta)=1 carries a faithful Euclidean simplex reflection realization, and translates of its closed fundamental alcove tile the slice. This realization agrees with the standard affine types. Source: math:thm-cg-affine-gram-classification-and-euclidean-realization; Statement (1)–(4), especially (2)–(3); proof steps 1.1–3.2.. Reading limits: Read the complete supplied statement, assumptions and proof. Import the canonical affine-slice and tiling interfaces under their actual hypotheses; do not infer an Artin normaliser theorem.
  • math:thm-cg-dual-chamber-intersections-and-point-stabilizers: For the finite-rank canonical Coxeter representation and f in the closed fundamental chamber, Stab_W(f)=WS(f), where S(f) is its set of zero simple-root coordinates. Source: math:thm-cg-dual-chamber-intersections-and-point-stabilizers; Statement (4); proof steps 1.2–3.1.. Reading limits: Read the complete supplied item and proof. Apply it only to the explicitly constructed fundamental-face point in step 6.
  • math:thm-cg-tits-cone-interior-and-local-finiteness: For a finite-rank canonical Coxeter representation, every compact subset of the interior of its Tits cone meets only finitely many root hyperplanes. Source: math:thm-cg-tits-cone-interior-and-local-finiteness; Statement (3), compact-subset conclusion; proof steps 4.1–6.1.. Reading limits: Read the supplied statement and proof. The application is inside the ambient interior established independently in step 3; it does not use the original article’s disputed boundary-ball inference.
  • math:lem-a-finitely-punctured-disk-retracts-to-a-wedge-of-circles: An open disk minus finitely many distinct points has the homotopy type of a finite wedge of circles and has zero homotopy groups in every degree at least two, including the unpunctured case. Source: math:lem-a-finitely-punctured-disk-retracts-to-a-wedge-of-circles; Statement; proof steps 1.1–6.1.. Reading limits: Read the supplied lemma, including its finite spine and tree-cover arguments. Apply it to one disk containing a given compact sphere image, not directly to an infinite puncture set.
  • finite-cw-homology: Continuous maps induce homology homomorphisms, homotopy equivalences preserve homology, H1(S1;Z)=Z, and the homology of a CW complex is computed by its cellular chain complex. In particular, finite CW complexes have finitely generated H1. Source: https://pi.math.cornell.edu/~hatcher/AT/ATch2.pdf; Printed p.111, Proposition 2.9 and Corollary 2.11; p.114, Corollary 2.14; pp.139–140, Theorem 2.35 and consequence (ii).. Reading limits: Current author read these extracted passages from the retained full-book PDF, including the homotopy-invariance proof opening on p.112. The meridian evaluations and affine root calculation in step 8 are local arguments. No full-chapter reading or supplier audit is claimed.
  • classical-affine-asphericity: For an irreducible affine Coxeter group, its ordinary orbit configuration space is a classifying space for the corresponding Artin group. Theorem 8.14 supplies the deformation retraction used in Theorem 8.15. Source: https://arxiv.org/html/1907.11795v2; Introduction, Main Theorem; §8, Theorems 8.14–8.15 and their proof paragraphs.. Reading limits: Current author read the abstract, introduction and exact theorem statements with their concluding proof paragraphs. The discrete-Morse proof was not reconstructed. No nonempty-J or normaliser conclusion is imported.
  • release-status: Primary overview entry 254 advertises an asphericity result for ordinary finite-rank Artin Salvetti complexes and links a manuscript. The overview is not itself a verified theorem about the relative normaliser complement. Source: https://github.com/openai/math/blob/main/overview.tex; resultentry{254}, Classifying spaces and geometric obstructions for Artin groups.. Reading limits: Current author checked the entry and its linked manuscript location, but did not read or verify the manuscript. The unchanged inventory record also retains the assessor’s earlier failed raw-PDF retrieval; that retrieval is not claimed as a new attempt.
Independent review

Decision: accept

Accept unchanged as a partial development and research question, not as a solution of Conjecture 1.10. Steps 2–8 establish the stated geometric subresults under the affine hypotheses. Steps 9–10 correctly leave the Artin normaliser comparison and higher-dimensional relative asphericity unresolved.

Dependency review: Checked every numbered inference. The positive-radical and affine-realization suppliers apply to connected positive-semidefinite corank-one canonical data. Height invariance and alcove tiling give U={h>0}∪{0}; properness of J makes h nonzero on EJ. Complex division by h(z) gives the claimed homeomorphism with a contractible quadrant factor. The r=1 fixed-space and point-stabilizer argument proves G=1. For r=2, compact subsets of FJ lie in the ambient interior, so the independent local-finiteness supplier applies; each sphere map then lies in a finitely punctured disk. Exact rational reflection multiplication verifies the affine Ã₂ root sequence used for the independent meridian classes. Hatcher’s homology results give the finite-CW obstruction. No conjecture or disputed article inference supplies these deductions. The article supplies formulation and attribution only. Paolini–Salvetti, §2.1 and Theorems 8.14–8.15, concerns the ordinary affine configuration space; it supplies no nonempty-J normaliser comparison. The primary overview, entry 254, is used only as advertisement/status evidence. All mathematical inputs inspected are mathematical suppliers; no physical premise is used. No logical dependency cycle was found in the direction’s argument.

Review reading limits: Read the complete assigned draft and its ten argument steps, the immediate mathematical supplier formulations and applicable hypotheses, and the original passages needed for attribution and defect assessment. Inspected rendered PDF pp.4,6,8–11,13,16,22,23,25,29–30, together with surrounding extracted text. Read all three requested escalation evidence files and independently recomputed the boundary recurrence, D₄ word evaluations and affine Ã₂ calculation. Reassessed all eight prior report findings: retain the Lemma 3.5 induction issue with corrected evidence, root inclusion, diagonal ribbon qualification, unrestricted finite-CW failure, normaliser-versus-quotient wording, D₄ word typo, equality-only adjacency wording, and omitted surjectivity argument. The adjacency example challenges only the literal equality-only wording; the finite-CW example does not challenge spherical Remark 6.15. Screened the 242 supplied earlier comparisons against their source passages: 220 concern generated content, 15 remain dismissed as original-article evidence, and seven support the existing source findings. This is an attribution reassessment, not a renewed audit of every generated proof. Read the cited Paolini–Salvetti statements and concluding proof paragraphs, primary overview entry 254, Paris’s retained Salvetti construction and Theorem 3.1, and Hatcher’s relevant homology passages. Did not reconstruct the discrete-Morse theorem, audit supplier literature, read the release manuscript, or repeat the inherited 143-item assessment. Inherited reading histories are not claimed as this reviewer’s work.

Remaining gaps

No isomorphism of the two extensions is constructed, including in rank three. For |S\setminus J| at least three, asphericity of the normalized restricted arrangement is also left unresolved. The proved vanishing concerns the upstairs complement; no unproved quotient or Artin-group identification is included. Finite CW type upstairs is not assumed: an explicit nonempty-J affine example below has infinitely generated first homology.

Author and reviewer gaps

  • No mutually inverse comparison between the Artin normaliser extension and the geometric covering extension has been constructed or independently sourced for the entire assigned family.
  • For maximal proper J, the remaining algebraic test is Norm_A(AJ)=AJ. Triviality of the Coxeter normaliser quotient does not prove this Artin statement.
  • When |S\setminus J| is at least three, the normalized restricted affine arrangement has complex dimension at least two; its asphericity is not established here. Ordinary affine asphericity cannot be applied without identifying an applicable arrangement model.
  • The proved low-dimensional higher-homotopy vanishing is for the upstairs complement. A complete classifying-space conclusion downstairs still requires the covering and group comparison with all relevant hypotheses checked.
  • The primary release manuscript was not read or accepted as an input. The current-status search was targeted and cannot establish that no relevant resolution exists.
  • The reproduced source records retain the frozen assessor’s reading history. This author did not repeat all 143 item assessments or all 242 earlier-finding comparisons and supplies no independent closeout or review stamp.
  • The rank-three boundary sequence was checked against rendered Proposition 3.6, p.9, including its formal recurrence. It refutes the ambient-ball inference, while its points leave EJ and do not refute relative local finiteness. Its infinite parabolic J is outside the proper-parabolic affine setting used above. The D4 word defect and unrestricted finite-CW defect were also checked against rendered pp.30 and 13; they remain existing report findings rather than new evidence against this affine question.
  • No compatible isomorphism between the algebraic normaliser extension and geometric covering extension is established for the whole assigned family.
  • For maximal proper J, the remaining algebraic assertion is Norm_A(AJ)=AJ; triviality of the Coxeter quotient does not prove it.
  • For |S\J|≥3, asphericity of the normalized restricted arrangement complement is not established here.
  • The rank-three argument proves higher-homotopy vanishing upstairs; it does not identify the quotient fundamental group with N(A,J).
  • The current-status search is bounded. The primary release manuscript was not verified and supplies no relative theorem.
Sources and reading limits · 4
  • Normalisers of parabolic subgroups of Artin–Tits groups and Tits cone intersections: https://arxiv.org/abs/2509.21915; Frozen arXiv v3, 30 July 2026, PDF pp.1–33; §§1–7; bibliography and affiliations; Conjecture 1.10, p.4; Theorem 1.8, p.3; Theorem 6.7, p.26; Corollary 6.14 and Remark 6.15, p.27; arXiv submission-history page checked 2026-11-14. Reading limits: Read every frozen extracted page and all 33 rendered page images; additionally viewed pp.9,10,30 at native resolution. Checked all 143 original item formulations against the PDF, and read their complete source arguments. Checked the arXiv history on 2026-11-14: v3 remains displayed. The inventory and prior report are leads, not proof suppliers. Bibliography works were not comprehensively reread.
  • Giovanni Paolini and Mario Salvetti, Proof of the K(π,1) conjecture for affine Artin groups: https://arxiv.org/html/1907.11795v2; Introduction, Main Theorem; §8, Theorems 8.14–8.15 and their proof paragraphs. Reading limits: Read the abstract, main theorem, and extracted Theorems 8.14–8.15 with their final proof paragraphs. Import only classical affine asphericity under the stated hypotheses; did not reconstruct the discrete-Morse proof or infer nonempty-J normaliser statements.
  • OpenAI mathematics release — primary overview: https://github.com/openai/math/blob/main/overview.tex; overview.tex, resultentry{254}: Classifying spaces and geometric obstructions for Artin groups. Reading limits: Read only primary release entry 254 and its manuscript link. It advertises a classical finite-rank resolution; the raw PDF fetch failed with unsupported content type. This is status evidence only: no proof acceptance, formalization check or implication for the relative conjecture is claimed.
  • Allen Hatcher, Algebraic Topology, Chapter 2: https://pi.math.cornell.edu/~hatcher/AT/ATch2.pdf; §2.1, homotopy invariance, printed pp.110–112; §2.2, cellular homology, printed pp.139–140; §2.2, Theorem 2.44, printed pp.146–147. Reading limits: Read extracted homotopy-invariance, cellular-chain and Euler-characteristic passages; use the standard finite-chain finiteness implication. The infinite-dihedral meridian calculation is local. Did not read the complete chapter or audit this supplier.