Research / graceful-spider-three-arms

Three equal long arms: zero-rotatability at lengths three and four

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For every integer m >= 1, the spiders S(3,3,3,1^m) and S(4,4,4,1^m) admit a graceful labeling with zero at any chosen vertex. Eleven base labelings and a threshold-insertion lemma prove both families.

The result

For every integer m >= 1, both S(3,3,3,1^m) and S(4,4,4,1^m) are 0-rotatable: any chosen vertex can carry zero in some graceful labeling. Each tree has three equal long arms and m extra leaves at the center. If it has q edges, a graceful labeling uses the vertex labels 0,...,q and the edge differences 1,...,q, each exactly once.

How the proof works

Five explicit labelings cover the vertex types in the length-three family at m=1; six cover those in the length-four family. A threshold-insertion lemma then adds one center leaf at a time. It preserves both the required edge differences and the vertex labeled zero. Induction gives the result for every m, beyond the finite cases checked by the accompanying programs.

The research note contains the eleven labelings, the two-case insertion proof, and the relation to earlier work. The package contains the base data, Python checkers, and source notes. SHA-256: 86b4e0f5c01a8f43a4579894e891a3ef362c675280ca70a75b9df790b064b549.

The public repository provides the base certificates, checkers and a GitHub-readable copy of the existing research note.

Scope and earlier work

Patterson's 2017 thesis proposed a broader conjecture about 0-rotatable spiders. Other papers established gracefulness or 0-rotatability for related families, and a related label-gap insertion method was described before this work. Our targeted search did not locate the two exact all-m statements, but their publication priority remains unresolved.

The proof concerns exactly three long arms, all of length three or all of length four, with at least one extra center leaf.

Statements & evidence

SPIDER-333-LEAVES-0-ROTATABLE Proof provided

For every integer m >= 1, S(3,3,3,1^m) is 0-rotatable: every prescribed vertex can receive label zero in a graceful labeling.

Formal verification
No formal verification
Review status
Internal check
Evidence
Five m=1 label certificates and the fixed-threshold insertion lemma; independent internal audit in graceful-spider-three-arms-proof.zip (SHA-256 86b4e0f5c01a8f43a4579894e891a3ef362c675280ca70a75b9df790b064b549), audit.md.
Scope
Exactly three arms of length three and at least one additional center leaf; all integer m >= 1. No result for arbitrary spiders or arbitrary numbers of length-three arms. Publication priority unresolved.
Assumptions
Graceful labels use each integer 0..m+9 once; edge differences use 1..m+9 once. The graph is S(3,3,3,1^m).
Toolchain
Elementary written induction; Python 3.12.1 checks the base certificates and finite invariant instances. No formal proof assistant.
Reviewer
Independent internal AI mathematical audit, 8 October 2026; no external or peer reviewer.

SPIDER-444-LEAVES-0-ROTATABLE Proof provided

For every integer m >= 1, S(4,4,4,1^m) is 0-rotatable: every prescribed vertex can receive label zero in a graceful labeling.

Formal verification
No formal verification
Review status
Internal check
Evidence
Six m=1 label certificates and the fixed-threshold insertion lemma; independent internal audit in graceful-spider-three-arms-proof.zip (SHA-256 86b4e0f5c01a8f43a4579894e891a3ef362c675280ca70a75b9df790b064b549), audit-k4.md.
Scope
Exactly three arms of length four and at least one additional center leaf; all integer m >= 1. No result for arbitrary spiders or other arm lengths. Publication priority unresolved.
Assumptions
Graceful labels use each integer 0..m+12 once; edge differences use 1..m+12 once. The graph is S(4,4,4,1^m).
Toolchain
Elementary written induction; Python 3.12.1 checks the six base certificates and finite invariant instances. No formal proof assistant.
Reviewer
Independent internal AI mathematical audit, 8 October 2026; no external or peer reviewer.

Contributions & AI assistance

Contributions

School Scotty is an AI-assisted research program maintained by Jordi Gartner.

AI assistance

AI helped find the eleven base labelings, shape the insertion proof, build the checkers and translate selected passages of the page. Two separate AI audits checked the arguments; their reports are in the proof package. No external review has taken place.

References

  1. B. J. Patterson, New Classes of Graceful Spiders and Related Computational Results, MSc thesis, Ball State University (2017), Conjecture 5.4.4
  2. R. I. Rofa, 0-rotatability of classes of rooted symmetric trees (2023)
  3. P. Bahls, S. Lake and A. Wertheim, Gracefulness of families of spiders, Involve 3 (2010)
  4. A. Panpa, S. Imnang and T. Wasuanankul, Graceful Labeling of Spider Graphs With at Most Five Legs, Journal of Applied Mathematics (2025)
  5. MathWorld, Graceful Tree Theorem, 2026 discussion of a label-gap insertion method attributed to E. Pegg Jr. (secondary account)

Related releases

  1. A certificate-and-composition proof of 0-rotatability for S(k^n,1^m), k in {3,5,7,9,11}, n >= 2, m >= 0. Established ingredients and prior subfamilies are credited; publication priority remains unresolved.

    · Research note

  2. For every even K≥20, attach two K-edge arms to the chosen zero-labeled root of any finite graph H with a supplied conventional graceful labeling. On either new arm, each depth 2≤d≤D8(K) separately admits a conventional graceful labeling with zero at that vertex. The guaranteed depth interval grows without bound.

    · Research note

  3. For every integer k≥19, all n≥2,m≥0 and any selected long arm of S(k^n,1^m), each depth 2≤d≤D8(k) can receive zero in a graceful labeling. Separate requests may use separate labelings. The explicit sufficient prefix includes both length parities and has limiting proportion 10/11; no optimality or historical priority is claimed.

    · Research note

  4. For any finite graph H with a conventional graceful labeling and a chosen root labeled 0, attach two named arms of K=23+24t edges, where t≥1. On each new arm, a separate conventional graceful labeling can place zero at depth 20+22t or 21+22t.

    · Research note

  5. For k=23+24t, n≥2 and m≥0, every selected named long-arm vertex at depth 17+20t through 20+22t can be zero in its own graceful labeling for every integer t≥0. For t≥1, the same holds at the additional depth 21+22t. For t≥2, it also holds at depth 22+22t. Consequently, for t≥5 the q24/D8 prefix and q48 point combine to give all depths 1≤d≤22+22t.

    · Research note

  6. Given a finite graph with a supplied graceful labeling that assigns zero to a chosen root, attach two new 119-edge arms there. Every interior depth 1–118 on either arm can receive zero in its own labeling. The source also proves eight specified near-tip depths for K=30·4^r−1, r≥1.

    · Research note

  7. Given any finite graph with a conventional graceful labeling that assigns zero to a chosen root, attach two 95-edge arms at that root. Each interior vertex on either new arm can receive zero in its own graceful labeling.

    · Research note

  8. For every integer m≥1 and every prescribed vertex of S(7,7,7,1^m), there exists a graceful labeling that assigns zero to that vertex. Five base certificates, four complements, and a leaf-insertion lemma prove the result; publication priority remains unresolved.

    · Research note

  9. For every n ≥ 2 and m ≥ 0, each actual vertex of S(23^n,1^m) can be assigned zero in a graceful labeling, with a separate labeling for each selected vertex.

    · Research note

  10. For every n ≥ 2 and m ≥ 0, every actual vertex of S(25^n,1^m) can receive zero in a graceful labeling, with a separate labeling for each selected vertex.

    · Research note

  11. For every n ≥ 2 and m ≥ 0, each actual vertex of S(47^n,1^m) can be the unique zero in a graceful labeling; a separate labeling may be used for each target.

    · Research note

  12. For every n ≥ 2 and m ≥ 0, each actual vertex of S(71^n,1^m) can be the unique zero in a graceful labeling; a separate labeling may be used for each target.

    · Research note

  13. For every n≥2 and m≥0, each vertex of S(95^n,1^m)—the hub, any of its m original leaves, or any position on any named 95-edge arm—can be assigned zero in its own graceful labeling.

    · Research note

  14. For every even k ≥ 2, n ≥ 2, and m ≥ 0, each named vertex of S(k^n,1^m) can receive zero in a graceful labeling, with a separate labeling for each chosen vertex.

    · Research note

  15. For every integer m >= 1, both S(3,3,3,1^m) and S(4,4,4,1^m) are 0-rotatable. Eleven explicit base labelings and one threshold-insertion lemma give a written proof for all m.

    · Research note

Version history

VersionPublishedChange note
v12Added a contiguous prescribed-zero prefix for every integer arm length k≥19 with limiting proportion 10/11, completed additional residue classes and supplied explicit depth bounds and reproducible proof sources.
v11Adjusted the link to the growing-depth research note to match each page’s language.
v10Adds a construction for prescribed zeros at long-arm depths 4s and 4s + 1 in S(k^n,1^m), where k = 2r + 1, s ≥ 1, r ≥ 3s, r ≠ 3s + 1, n ≥ 2, and m ≥ 0. The number of guaranteed depths grows with k; this is not a full zero-rotatability result. The two zero positions use separate spider labelings.
v9Corrected wording about the existing note and the separate K7 proof archive in English and German.
v8Removed repeated literature caveats and clarified the role of finite program checks.
v7Added a proof note for the five odd arm lengths k = 3, 5, 7, 9, and 11, for n ≥ 2 and m ≥ 0.
Archived wording

Adds a separate two-parameter family note for k in {3,5,7,9,11}, n >= 2, m >= 0. The previous k=3,4 and K7 notes retain their own versions and archives. Publication priority unresolved; DE/ZH remain translation drafts.

v6Added the separate K7 certificate proof and extended the project scope to k in {3,4,7}, m >= 1; corrected Patterson full-text availability and prior alpha-gracefulness. DE/ZH remain translation drafts.
v5Clarified AI roles in the research, proof development and checks, internal review scope, and editorial responsibility.
v4Set School Scotty as the research-program signature and clarified Jordi Gartner's editorial responsibility and the specific AI contributions.
v3Added German and Chinese translations of the existing claim evidence, scope, assumptions, toolchain and reviewer information. The claims, proofs, statuses and English source text are unchanged; the review status stayed the same.
Archived wording

Added German and Chinese translations for existing claim evidence, scope, assumptions, toolchain and reviewer metadata only; no claim, proof, status, source text or review-status promotion.

v2Revised the English, German and Chinese project overview and linked the existing research note and public repository; the theorem claims, evidence and references are unchanged.
v1Initial project page for two internally audited 0-rotatability theorems, for three long arms of length three or four with m>=1 center leaves; novelty and priority remain unresolved.

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