Bugeaud–Durand dimension conjecture for rationally approximable points in the Cantor set

Let KK be the middle-third Cantor set and let W(v)W(v) denote the set of real numbers satisfying the relevant Diophantine approximation condition with exponent vv. Then

Bugeaud–Durand conjecture.

dimH(KW(v))=max{dimH(K)1+2v+1,dimH(K)v+1}.\dim_H(K\cap W(v))=\max\left\{\dim_H(K)-1+\frac{2}{v+1},\frac{\dim_H(K)}{v+1}\right\}.

Bugeaud and Durand had established an almost-everywhere upper bound for translates of the middle-third Cantor set. The supplied source does not resolve whether this exact formula holds, so the conjecture remains open.

Sources & referencesView supporting material

Primary source

Suxuan Chen, “The Hausdorff dimension of the intersection of ψ-well approximable numbers and self-similar sets”, arXiv:2510.17096 (2025).

Additional references

3 papers in this index state this conjecture (2021–2025). The statement above is taken from the most recent of them; the others are arXiv:2402.18395, arXiv:2101.05910.

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