Five orientations of a 32-leaf tree miss exactly one leaf pair
Abstract
An orientation cover of size m of a finite tree T is a family o₁,…,oₘ of orientations of the edges of T such that every pair of leaves is joined by a directed path in at least one oᵢ; the least such m is the orientation cover number oc(T), and by results of Fitzpatrick–Nowakowski and Brigham–Chartrand–Dutton–Zhang it is the least dimension of an isometric embedding of the path metric of T into (ℝᵐ,| · |_∞); Chalmers extends the identification to every assignment of positive edge lengths. He recently exhibited a cubic tree T on 62 vertices and 32 leaves with oc(T)=6, refuting the conjecture D(t)=⌈log₂ t⌉ — the exact form of the sharp-constant conjecture of Brigham, Chartrand, Dutton and Zhang, and the unweighted case of the conjecture of Aksoy–Ki li ç–Koçak. His argument shows that five orientations do not suffice; it does not say by how much they fail. We show that they fail by exactly one pair: the maximum number of the C(32, 2)=496 leaf pairs of T that five orientations can jointly join is 495, and it is attained by an explicit family that misses only the pair formed by the two leaves adjacent to one common vertex. The upper bound here is Chalmers' theorem, for which we also give what appears to be the first machine-checked proof: a branch-state recurrence with dominance pruning, run once outside the prover and then replayed inside it against a certificate. The recurrence is one-sided by construction — the states it manipulates over-approximate what five orientations realise — so a defective certificate costs a recomputation and never soundness; it settled the exclusion in under a minute of scripting time — 30 seconds of it producing the certificate verified here — where a direct SAT encoding did not close in 600 seconds. Every assertion below about a specific tree is verified in Lean 4.
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Source snapshot 2026-08-30 15:34 UTC
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Claim ledger
Stated results
OC1known data2026-08-28
The Lean tree term is the tree of the source's Table 1: reading the vertex labels and edge indices off the rooted term and sorting by edge index reproduces, for each of the 61 lexicographic edges eᵢ = (u,v) with u < v, the child/parent pair the printed parent map assigns to it; 32 distinct leaves, 61 edges, root branches of 4, 13 and 15 leaves
OC2known data2026-08-28
oc(T) <= 6: the six hexadecimal masks of the source's Table 2, decoded under its stated bit convention, join all 496 leaf pairs of T by directed paths; and none of the six is redundant – for each of them there is a leaf pair the other five miss
OC3known2026-08-28
oc(T) >= 6: no five orientations of the 61 edges of T join every pair of its 32 leaves by a directed path – a kernel-bound proof of the source's refutation, by structural induction over the rooted tree against a validated branch-state certificate, with the reasoning layer (branchₛound) free of native_decide
OC4known2026-08-28
oc(T) = 6 exactly: 6 is the least m for which T has an orientation cover of size m, so D(32) >= 6 > 5 = ceil(log2 32) and the Brigham-Chartrand-Dutton-Zhang and Aksoy-Kilic-Kocak conjectures fail
OC5candidate2026-08-28
The exact five-orientation coverage maximum of T is 495: five orientations join at most 495 of the 496 leaf pairs, and an explicit family attains 495, missing only the pair 3,4
OC6routine2026-08-28
Control: the balanced 32-leaf cubic tree (root branches of 10, 11 and 11 leaves) DOES have an orientation cover of size five, under exactly the definitions that make OC3 a statement about T
OC7known2026-08-29
The leaf-record bound for every tree of the model at once: if m orientations join every pair of leaves of a rooted tree whose non-leaf vertices all have degree three, then it has at most 2 ^ m leaves; hence oc T > 4 for the source's tree with no branch-state certificate and no native_decide in the proof layer
OC8candidate2026-08-29
A tree with t leaves admitting a K-robust m-cover – m orientations plus a set F x of at least K forbidden coordinates at each leaf, every pair still joined outside F x u F y – satisfies t * (K + m) <= m * 2 ^ m; and oc <= rc_K <= oc + K
OC9routine2026-08-29
No tree with exactly 2 ^ m leaves has a robust m-cover; in particular the balanced 32-leaf tree TB, which does have a five-orientation cover, has no robust one, while it does have a robust 6-cover
OC10routine2026-08-29
The common-alive bound: the coordinates in which every leaf of a branch reaches its attachment edge join no pair inside that branch, so the remaining coordinates already cover the branch internally, and |C| + ocᵢ(branch) <= m
OC11routine2026-08-29
6 <= rc T <= 7 and 6 <= rc₆ T <= 12 for the source's tree, where rc_K is the least m admitting a K-robust m-cover
OC12routine2026-08-29
At the smallest tree where the notions separate – two cherries on an edge, four leaves – oc = 2, rc = 3, and oc of the cherry-substituted 8-leaf tree is 3, all three exactly
OC13routine2026-08-29
6 <= oc (T[cherry]) <= 7 for the 64-leaf tree obtained by hanging a cherry at each of the 32 leaves of the source's tree – the cell whose value decides whether the substitution route can produce a second tree with oc > ceil(log2 t)
OC19candidate2026-08-29
The converse transport: an m-cover of the cherry-substituted tree reads back down to a robust m-cover, so rc R = oc (R[cherry]) exactly for every tree of the model and every m; at the source's tree, oc (T[cherry]) = 6 iff T has a robust 6-cover, and = 7 iff it does not
OC14candidate2026-08-29
A robust m-cover of any tree covers the cherry-substituted tree in the same m coordinates – no extra coordinate – and hence a tree with t leaves and a robust m-cover satisfies 2 t <= 2 ^ m
OC15measurement2026-08-29
MEASUREMENT: the K-robust m-cover question for the source's tree as a SAT instance in the family's pivot model, with its positive control
This ledger entry is reported in prose and is not bound to a Lean theorem.OC16measurement2026-08-29
MEASUREMENT: what the general layer cost to formalize
This ledger entry is reported in prose and is not bound to a Lean theorem.OC17known2026-08-29
For every k: the k-fold cherry iterate of a tree with exactly 2 ^ m leaves and an m-cover has cover number exactly m + k; instantiated to two infinite families – oc (TB[cherryᵏ]) = 5 + k at 32 * 2ᵏ leaves, and oc (R4[cherryᵏ]) = 2 + k with no native_decide anywhere in its proof
OC18candidate2026-08-29
The ladder cap for the source's tree: for every k, the k-fold cherry iterate of T has 32 * 2ᵏ leaves and 5 + k <= oc <= 6 + k = ceil(log2 (32 * 2ᵏ)) + 1, so the doubling ladder's defect stays at most one forever and provably cannot refute the source's Problem 5.1
OC20candidate2026-08-30
The K-robust cover number is the orientation-cover number of the K-fold cherry tower: for every tree of the model, every m and every K, m orientations together with a set of at least K forbidden coordinates at each leaf (every pair still joined outside both sets) exist exactly when the tree obtained by grafting the perfect binary branch on 2 ^ K leaves at every leaf has an m-cover. Hence the sharp count 2 ^ K * t <= 2 ^ m, and rc_K R = oc R + K exactly for every tree whose cover number meets the leaf bound (2 ^ a < 2 t, the leaf count not necessarily a power of two)
OC21candidate2026-08-30
At the source's tree: 5 + K <= rc_K T <= 6 + K for every K, so 11 <= rc₆ T <= 12 where the family's record was 6 <= rc₆ T <= 12; the (m, K) = (11, 6) design question this family ran as a SAT experiment is rung 6 of the doubling ladder, oc (T[cherry⁶]) = 11 at 2048 leaves; and the family's two open searches are ordered – a robust 6-cover of T implies a 6-robust 11-cover – so a refutation at (11, 6) settles the 64-leaf cell at oc (T[cherry]) = 7
OC22routine2026-08-30
Once a rung of the cherry tower meets the leaf-record bound, every later rung does; so every rung of the doubling ladder over the source's tree has cover number 5 + k or 6 + k, the value 5 + k propagates upwards, and the whole ladder is described by a single threshold
OC23candidate2026-08-30
The ladder's infinitely many open cells collapse to one. In a K-robust m-cover each leaf has only m - K free coordinates and a pair can only be joined in a coordinate free at both ends, so if t (m - K) < m some coordinate is forbidden at every leaf and can be deleted at the cost of one coordinate and one unit of robustness; hence some rung of the doubling ladder over the source's tree meets the leaf-record bound if and only if rung 155 does
OC24measurement2026-08-30
MEASUREMENT: the price of the m = 6 branch-state recurrence, run in its cheapest form (the ROBUST recurrence on the 32-leaf tree T itself rather than the plain one on the 64-leaf T[cherry]), with its positive control – and the answer is that it is not affordable in Python
This ledger entry is reported in prose and is not bound to a Lean theorem.Provenance
- Generated by
- Machina Mathematica
- Released by
- Korea Superintelligence Labs
- Source context
- For a finite tree T let dim_∞(T) be the least m such that the path metric of T embeds isometrically into (Rᵐ, ‖·‖_∞), and set
- Snapshot
- 2026-09-07 03:53 UTC
- Ledger commit
801848d7