Refinement monotonicity of normalized Witten intersection numbers, and the nesting conjecture at genus 14–18
Abstract
Guo, Yang and Zagier (arXiv:2603.15233) normalise Witten's psi-class intersection numbers as C(d)=2²ᵍ∏ⱼ(2dⱼ+1)!! / (3²ᵍ⁻²⁺ⁿ(2g-3+n)!)∫_(overline(M)_(g,n))psi₁^(d₁)…psiₙ^(dₙ) and conjecture (their Conjecture 1) that for g ≥ 2 and d₁,…,dₙ ≥ 1 of genus g one has C(3g-2) ≤ C(d) ≤ C(2³ᵍ⁻³). Their Lemma 2 proves the lower inequality, and they report the upper one checked for dⱼ ≥ 2 and g ≤ 13. We verify the upper inequality, in exact rational arithmetic and over the complete set of tuples with all dⱼ ≥ 2, at genus 14 to 18 (560 709 further tuples), with 2³ᵍ⁻³ the unique maximiser at each genus. We then observe a stronger statement that the source does not make: indexing the tuples of genus g with all dⱼ ≥ 2 by the partitions λ=d-1 of 3g-3, the value C increases strictly whenever one part of λ is split into two. We verify this at every genus 2 ≤ g ≤ 18, over 11 514 074 single-split steps. Since (3g-3) and 1³ᵍ⁻³ are the two extremes of the refinement order, refinement monotonicity implies the nesting inequalities, with strict inequalities off the extremes and uniqueness of both extremisers; and it is the only one of the natural orders left standing, since the length-then-lexicographic order of Guo, Norbury, Yang and Zagier, weak monotonicity in the length, and the dominance order all fail for these numbers, by examples printed in the source or read off its Table 1. All values are computed through the Dijkgraaf–Verlinde–Verlinde recursion in an integer normalisation, controlled against the one-point formula, Zograf's two-point formula and the dilaton relation, and the whole check is verified in Lean 4.
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Claim ledger
Stated results
WN1known2026-09-07
The compute-first gate: all fourteen exact rational values printed in Table 1 (p. 4) of arXiv:2603.15233v1 reproduced from the DVV recursion, together with two exact-rational instances of the dilaton relation Eq. (32), C(1,4) = C(4) = 35/144 and C(1,1,2,2,2) = C(2,2,2) = 175/648.
WN2known2026-09-07
The four exact values and the four strict comparisons printed in the numbered Remarks (all on p. 5) of arXiv:2603.15233v1: C(0⁶,10) = 1616615/6718464 < C(4) and C(2³) < C(0,0,6) = 5005/15552 (the nesting fails once dⱼ = 0 is allowed), C(2⁵,8) = 727759375/2448880128 < 419588015525/1410554953728 = C(3⁴,5) (weak monotonicity in the length fails), and C(4,4) < C(3,5) (the [GNYZ] lexicographic monotonicity fails).
WN3known2026-09-07
Engine controls at every genus 2 <= g <= 18, inside the same kernel check as the results: the one-point formula Eq. (19) in the form W(3g-2) = (6g-3)!!; Zograf's independent explicit two-point formula Eq. (44) in the integer form W(d₁, 3g-1-d₁) * g = zografS(g,d₁) at all 3g two-point cells of each genus; the dilaton relation Eq. (32) in the form W(1,d) = 3(2g-2+n) W(d) at every one of the 600,492 primitive tuples; and that the enumeration really is the primitive locus (each tuple has all parts >= 2, degree 3g-3+n and genus g).
WN4known2026-09-07
The lower half of the source's Conjecture 1, C(3g-2) <= C(d), verified over the COMPLETE primitive locus of every genus 2 <= g <= 18 (600,492 tuples, p(3g-3) of them at genus g), with the strengthening that (3g-2) is the UNIQUE minimiser at each genus.
WN5known data2026-09-07
The OPEN half of the source's Conjecture 1, C(d) <= C(2³ᵍ⁻³), over the complete primitive locus of every genus 2 <= g <= 13 (39,783 tuples), with 2³ᵍ⁻³ the unique maximiser at each genus.
WN6candidate2026-09-07
Genus 14, past the source's reported range: C(d) <= C(2³⁹) for each of the p(39) = 31,185 primitive tuples of genus 14, with 2³⁹ the unique maximiser. By the source's Eq. (32) this is equivalent to the full dⱼ >= 1 statement of its Conjecture 1 at this genus.
WN7candidate2026-09-07
Genus 15, past the source's reported range: C(d) <= C(2⁴²) for each of the p(42) = 53,174 primitive tuples of genus 15, with 2⁴² the unique maximiser.
WN8candidate2026-09-07
Genus 16, past the source's reported range: C(d) <= C(2⁴⁵) for each of the p(45) = 89,134 primitive tuples of genus 16, with 2⁴⁵ the unique maximiser.
WN9candidate2026-09-07
Genus 17, past the source's reported range: C(d) <= C(2⁴⁸) for each of the p(48) = 147,273 primitive tuples of genus 17, with 2⁴⁸ the unique maximiser.
WN10candidate2026-09-07
Genus 18, past the source's reported range: C(d) <= C(2⁵¹) for each of the p(51) = 239,943 primitive tuples of genus 18, with 2⁵¹ the unique maximiser. Together with WN6-WN9 this extends the source's verification from genus 13 to genus 18, i.e. by 560,709 further tuples.
WN11candidate2026-09-07
REFINEMENT MONOTONICITY, genus 2 to 13: indexing the primitive tuples of genus g by the partition lambda = d - 1 of 3g-3, splitting one part of lambda into two positive parts STRICTLY increases C. Verified at every genus 2 <= g <= 13 over 515,715 single-split steps (2, 21, 90, 328, 959, 2588, 6311, 14579, 31703, 66315, 133182, 259637 per genus), zero violations. Since (3g-3) is the unique refinement-minimum and 1³ᵍ⁻³ the unique refinement-maximum, this IMPLIES the source's Conjecture 1 at those genera, with strict inequalities off the two extremes.
WN12candidate2026-09-07
REFINEMENT MONOTONICITY at genus 14, 15, 16, 17, 18: 491,295 + 908,008 + 1,639,978 + 2,905,593 + 5,053,485 = 10,998,359 single-split steps, zero violations. With WN11 that is 11,514,074 split steps over genus 2 to 18, and it implies the open half of the source's Conjecture 1 at each of those genera.
WN13routine2026-09-07
Negative control, a too-large claim refuted: NEITHER half of Conjecture 1 survives dropping the hypothesis dⱼ >= 1. At g = 2 these are the source's own Remark (C(0⁶,10) < C(4) and C(2³) < C(0,0,6)); the genus-14 pair C(0⁶,46) < C(40) and C(2³⁹) < C(0,0,42) is computed here and shows the hypothesis is not an artefact of small genus.
WN14routine2026-09-07
Negative control, a too-small claim refuted: neither bound of Conjecture 1 can be narrowed. Replacing C(3g-2) by the next value up, or C(2³ᵍ⁻³) by the next value down, breaks the statement already at g = 3 – C(7) < C(2,6) and C(2,2,2,2,3) < C(2⁶). The uniqueness of the two extremisers, asserted at every genus in WN4 and WN5-WN10, is the same statement in general.
WN15routine2026-09-07
Negative control, a natural strengthening refuted: C is monotone in NEITHER direction of the dominance order on lambda = d - 1. lambda = (4,2) dominates (3,3) yet C(3,5) > C(4,4), while the global minimum sits at the dominance-largest partition (3g-3) and the global maximum at the dominance-smallest 1³ᵍ⁻³ (C(7) < C(2⁶) at g = 3). So dominance is not the order behind Conjecture 1; refinement, a proper suborder of reverse dominance, is.
WN16known2026-09-07
The dilaton reduction: because C(1,d) = C(d) exactly (the source's Eq. (32)) and a part dⱼ = 1 contributes 0 to sumⱼ (dⱼ - 1), deleting all the 1s preserves the genus and, for g >= 2, leaves a non-empty tuple with all parts >= 2. Hence Conjecture 1 for dⱼ >= 1 is EQUIVALENT, genus by genus, to Conjecture 1 for primitive d – so the source's primitive checks at g <= 13, and rows WN5-WN10 here, already carry the full dⱼ >= 1 statement at those genera.
This ledger entry is reported in prose and is not bound to a Lean theorem.Provenance
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- Source context
- Source. J. Guo, D. Yang, D. Zagier, *On uniform large genus asymptotics of Witten's intersection numbers*, arXiv:2603.15233 v1 (submitted 16 Mar 2026; the live abs page was checked on 2026-09-07 and shows a single version). Primary math-ph; cross-listed math.AG, math.CO, nlin.SI. Every numbered statement quoted below was read off the compiled e-print: curl -sSL https://arxiv.org/e-print/2603.15233v1 | tar xz gives Wnumbers.final.17.tex, which was compiled with tectonic, and the numbers come from the resulting.aux (newlabelconj
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- 2026-09-07 03:53 UTC
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