On a conjecture of Han and Xiong for fractional Gaussian binomial coefficients

Ken Ono

For positive rational u=c/d and r=a/b in lowest terms, with d even, d dividing lcm(b,2), and u≤r, the integer trace of the fractional Gaussian binomial coefficient at u dominates that at r coefficientwise for every k≥1. This proves the Han–Xiong comparison for every r≥1/2 and reduces the remaining parameters to 1/(2m).

Sources for this record

What was already known

Han and Xiong proved k≤3 and certain integer and half-integer families, and checked r=1/3 and 1/4 through k=150. The full comparison was open.

AI involvement AI-autonomous

Ken Ono reports that AxiomProver received the target statements and Han–Xiong paper without proofs, then generated the three theoretical statements and Lean proofs. Ono wrote the human explanation.

The three selected theoretical results and proofs were produced by AxiomProver from stated targets without supplied proofs; later human exposition does not change their origin.

Importance Notable

Proves the conjectured comparison on the full half-line r≥1/2 and narrows the remaining problem to a canonical family.

Limitations

The all-parameter, all-k conjecture remains open. A separate exact computation reaches k≤200; it is outside the three reported Lean proofs. Ono checked the formal statement correspondence, not every proof step by hand.

Technical verification Formal (Lean 4.31 with Mathlib and AxiomLib)

The paper reports sorry-free Lean 4.31 proofs for exactly Theorem 1.3, Corollary 1.4 and Theorem 1.5, and a human check that the formal statements express those results. The separate finite k <= 200 theorem is outside this formalized scope.

Formal checking

Sorry-free formal proof of the three statements; Ono checked their correspondence to the paper; source-reported.

Checker
Lean proof assistant, with statement alignment checked by Ken Ono
Scope
Support dominance, its r >= 1/2 corollary and canonical reduction, as Theorem 1.3, Corollary 1.4 and Theorem 1.5
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Full

Ono's Sections 1–3 explain the central support nesting and exponent-shift argument behind the three theoretical results.

Correction and publication history

2026-10-18 · publication

Proves the conjectured comparison on the full half-line r≥1/2 and narrows the remaining problem to a canonical family.

Read this published revision