Interpolated rational-sum approximation conjecture

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Let α\alpha be a real number, let N≥1N\geq 1 be real, and let 0≤β≤10\leq\beta\leq 1. The integers a1,a2a_1,a_2 and positive integers q1,q2q_1,q_2 satisfy 1≤q1,q2≤N1\leq q_1,q_2\leq N. Interpolated rational-sum approximation conjecture. There exist such integers a1,a2,q1,q2a_1,a_2,q_1,q_2 for which

∣α−a1q1−a2q2∣≤1(q1q2)βN2−β.\left|\alpha-\frac{a_1}{q_1}-\frac{a_2}{q_2}\right|\leq\frac{1}{(q_1q_2)^\beta N^{2-\beta}}.

The claim is known for the endpoint cases β=0\beta=0 and β=1\beta=1, while the cases 0<β<10<\beta<1 are left as an open problem.

References

Primary source

Tsz Ho Chan, “Approximating reals by sums of two rationals”, arXiv:math/0609322 (2007).

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