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

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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.

dim⁡H(K∩W(v))=max⁡{dim⁡H(K)−1+2v+1,dim⁡H(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.

References

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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