Conjecture on rational approximations with prescribed numbers of prime divisors

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Let α\alpha be a real number, let X≥1X\geq 1, let ϵ>0\epsilon>0, and let n≤ϵlog⁡Xn\leq \epsilon\log X be a natural number. Suppose that there are integers a,qa,q with 1≤q≤X1\leq q\leq X and (a,q)=1(a,q)=1 such that

∣α−a/q∣≤1/(qX).|\alpha-a/q|\leq 1/(qX).

Prescribed-prime-divisors conjecture. There is a rational number A/QA/Q such that Q≤X1+ϵQ\leq X^{1+\epsilon}, ω(Q)=n\omega(Q)=n, and

∣α−AQ∣≪ϵ1qX1−ϵ.\left|\alpha-\frac{A}{Q}\right|\ll_\epsilon\frac{1}{qX^{1-\epsilon}}.

This asserts that a rational approximation can be replaced by one with a prescribed number of distinct prime divisors in its denominator, with only a small loss in the approximation exponent. The supplied text gives heuristic motivation and related corollaries, but no resolution.

References

Primary source

Tsz Ho Chan, “Approximating reals by sums of rationals”, arXiv:0704.2805 (2007).

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