Weighted metric theorem for approximation by uniformly distributed sequences

Let nNn\in\mathbb N, let ω=(ωj)j1\omega=(\boldsymbol{\omega}_j)_{j\geq 1} be a sequence in [0,1]n[0,1]^n, and let Ψ=(ψ1,,ψn)\Psi=(\psi_1,\ldots,\psi_n) be an nn-tuple of non-increasing functions. Write Wω(Ψ)W_{\omega}(\Psi) for the associated weighted approximation set, and let λn\lambda_n denote nn-dimensional Lebesgue measure. Weighted metric theorem. For almost every sequence ω\omega in [0,1]n[0,1]^n, for every such Ψ\Psi we have

λn(Wω(Ψ))={0if j=1i=1nψi(j)<,1if j=1i=1nψi(j)=.\lambda_n(W_{\omega}(\Psi)) = \begin{cases} 0 & \textup{if } \displaystyle\sum_{j=1}^{\infty} \prod_{i=1}^n \psi_i(j) < \infty, \\ 1 & \textup{if } \displaystyle\sum_{j=1}^{\infty} \prod_{i=1}^n \psi_i(j) = \infty. \end{cases}

This would extend the cited non-weighted zero-one law to arbitrary coordinate-wise approximation functions. The preceding discussion notes that uniformly distributed sequences need not satisfy the divergent-case conclusion, so the conjecture concerns almost every sequence rather than every uniformly distributed sequence; its resolution is not given in the source.

Sources & referencesView supporting material

Primary source

Gerardo González Robert, Mumtaz Hussain, Nikita Shulga and Benjamin Ward, “Approximation by uniformly distributed sequences”, arXiv:2507.06583 (2025).

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