The qNCC-I quantitative Nonlinear Carleson Conjecture

From papers

Let \boldsymbol{\textstyle\gamma}=\\{\gamma_n\}_{n\in\mathbb{Z}_+} be the sequence of Verblunsky coefficients associated with the measure σ\sigma, and let M(ξ,σ)M(\xi,\sigma) denote the maximal function introduced above. qNCC-I. There is ϵ>0\epsilon>0 such that

{γn}2(Z+)ϵ\|\{\gamma_n\}\|_{\ell^2(\mathbb{Z}_+)}\le \epsilon

implies

TM2(ξ,σ)dσ{γn}2(Z+)2.\int_{\mathbb{T}}M^2(\xi,\sigma)\,d\sigma\lesssim \|\{\gamma_n\}\|^2_{\ell^2(\mathbb{Z}_+)}.

This is a quantitative strengthening of the Nonlinear Carleson Conjecture, proposing an L2L^2 bound for the nonlinear maximal function under a smallness assumption on the Verblunsky coefficients. Its resolution is not supplied in the source, so it remains open.

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Sources & referencesView supporting material

Primary source

Sergey A. Denisov, “Two quantitative versions of the Nonlinear Carleson Conjecture”, arXiv:2505.06788 (2025).

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