Velani's lacunary Khinchine convergence conjecture for the middle-third Cantor measure

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Let μ\mu be the middle-third Cantor measure, and let supp⁡(μ)\operatorname{supp}(\mu) denote its support. Let ψ\psi be an approximation function such that the sequence {ψ(2n):n≥1}\{\psi(2^n):n\geq1\} is non-increasing.

Velani's conjecture. If

∑nψ(2n)<∞,\sum_{n}\psi(2^n)<\infty,

then for μ\mu-almost every x∈supp⁡(μ)x\in\operatorname{supp}(\mu), the inequality

∥2nx∥<ψ(2n)\lVert 2^n x\rVert<\psi(2^n)

holds at most finitely often.

This is a lacunary convergence analogue of Khinchine's theorem without requiring monotonicity of the approximation function at all integers. The source attributes it to Velani and supplies no resolution.

References

Primary source

Han Yu, “Rational points near self-similar sets”, arXiv:2101.05910 (2021).

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