Chernoff's Density Is Strongly Log-Concave

Xianyang Zhang, Quan Zhou

Theorem 1 proves that the one-sided Airy factor g has v(x) = -(log g)''(x) > 0 and v(x) ≥ 4x. Since Chernoff's density f is proportional to g(x)g(-x), its curvature κ(x) exceeds 4|x| and has a positive global infimum. This proves strong log-concavity of the density of argmax_t{W(t)-t²}.

Sources for this record

What was already known

Balabdaoui and Wellner proved ordinary log-concavity of Chernoff's density in 2014, conjectured strong log-concavity, and gave numerical evidence. The Airy factorization and related identity used in the new proof came from earlier human work, including Menon and Srinivasan.

AI involvement AI-led

Zhang and Zhou credit GPT-5.6 Sol with the successful proof and strategy. They found an error in an earlier attempt, then carefully checked and revised the final argument; earlier human work supplied the Airy identity.

The authors explicitly credit GPT-5.6 Sol with the entire successful proof and strategy while documenting human review and revision.

Importance Notable

The model-origin proof addresses the 2014 strong log-concavity conjecture.

Limitations

The result concerns Chernoff's density, not all Brownian argmax laws. A separate human explanation of the central proof mechanism is not documented.

Technical verification Formal (human)

Both named authors explicitly say they carefully checked the final analytic argument after an erroneous first model attempt. This is source-reported completed human proof checking; no machine proof or independent reproduction is documented.

Formal checking

Careful human check of the final analytic argument with exposition revision

Checker
Xianyang Zhang and Quan Zhou, author-reviewers
Scope
Theorem 1's Airy-factor curvature bounds and resulting strong log-concavity of Chernoff's density
Basis
Reported by the linked checker
Evidence source

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

Human understanding Few

The paper says GPT wrote the proof and most exposition. Human checking and revision are documented, but a distinct human explanation of the central peeling and convolution mechanism is not; Few is the missing-evidence default, not a claim that the authors cannot understand it.

Correction and publication history