Mahler's rational-counting conjecture for the standard Cantor set

Let CC be the standard Cantor set, and let

N(s,t)={pqC:gcd(p,q)=1, sqt}.N(s,t)=\left\|\left\{\frac{p}{q}\in C:\gcd(p,q)=1,\ s\leq q\leq t\right\}\right\|.

Here gcd(p,q)=1\gcd(p,q)=1 means that the rational is written in reduced form. Mahler's rational-counting conjecture. For every ϵ>0\epsilon>0,

N(3n,3n+1)O(2(1+ϵ)n).N(3^n,3^{n+1})\in O\left(2^{(1+\epsilon)n}\right).

This conjecture gives the rational-counting estimate needed to establish the expected intrinsic approximation behavior on CC and would imply that the set of intrinsically very well approximable points has zero Hausdorff measure. The source reports computer evidence for it; its stronger possible bound N(3n,3n+1)O(2n)N(3^n,3^{n+1})\in O(2^n) is stated not to hold in forthcoming work, while the displayed conjecture itself is presented without a resolution.

Sources & referencesView supporting material

Primary source

Ryan Broderick, Lior Fishman and Asaf Reich, “Intrinsic Approximation on Cantor-like Sets, a Problem of Mahler”, arXiv:1106.0526 (2011).

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