The KLS constant is O((log n)¹ᐟ⁴)

Brayden Letwin

For every isotropic log-concave random vector X and symmetric matrix M, Var⟨MX,X⟩ ≤ 2 E|∇⟨MX,X⟩|². Letwin also derives a general KLS bound of order (log n)^(1/4).

Sources for this record

What was already known

The full KLS conjecture asks for a dimension-free Poincaré constant for all locally Lipschitz functions. Earlier moment-measure and Stein-kernel methods supplied parts of the framework, but the paper identifies no prior sharp quadratic-form inequality of this scope; earlier KLS bounds had a weaker logarithmic exponent.

AI involvement AI-centered

Letwin developed the moment-map approach and proved the matrix extension. ChatGPT 5.6 Pro suggested the key identity-matrix Hessian estimate and differentiated the Monge–Ampère equation. Letwin used those steps in the quadratic-form proof.

The model's retained B=Id Hessian estimate and Monge–Ampère differentiation supplied a central step; Letwin generalized it and completed the quadratic-form result.

Importance Notable

Establishes the sharp quadratic-form KLS inequality, a useful result for log-concave measures.

Limitations

The dimension-free conclusion covers quadratic forms, not all locally Lipschitz functions. A later paper reports a dimension-free general KLS bound. No completed check of Letwin’s full proof is documented.

Technical verification Reported

The v1 paper contains a detailed argument but does not document a completed proof check of the full quadratic-form theorem by a named human or machine. Reported is the evidence default; proof availability alone is not a check.

Human understanding Full

Letwin explains how the Hessian moment estimate, matrix extension, Stein kernel and H^(−1) trick combine to prove the quadratic-form inequality; the model-origin step is integrated into this account.

Correction and publication history

2026-10-18 · publication

The model supplied a central Hessian-estimate step; Letwin proved its matrix extension and the final inequality.

Read this published revision