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

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):n1}\{\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 xsupp(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.

Sources & referencesView supporting material

Primary source

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

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