number-theory / Diophantine approximation

The irrationality exponent of pi is 2

Theorem 1.1: μ(π)=2\mu(\pi)=2; for every ν>2\nu>2 there is Q(ν)Q(\nu) with ∣π−p/q∣≥q−ν|\pi-p/q|\ge q^{-\nu} for all p∈Zp\in\mathbb Z and q≥Q(ν)q\ge Q(\nu). Corollary: the Flint Hills series converges, and ∑n−a∣sin⁡n∣−b\sum n^{-a}|\sin n|^{-b} converges iff a>max⁡{1,b}a>\max\{1,b\}. The bound is NOT effective (no explicit Q(ν)Q(\nu)), and it is NOT a bound of the form c/q2c/q^2: bounded partial quotients for π\pi are not claimed. The method is an interpolation-determinant argument, not an improvement of the integral constructions behind earlier numerical bounds.

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number-theorySep 24, 2026Significance 60/100Registry: lean checked

The irrationality exponent of pi is 2

Prior state unknown→proved

Theorem 1.1: μ(π)=2\mu(\pi)=2; for every ν>2\nu>2 there is Q(ν)Q(\nu) with ∣π−p/q∣≥q−ν|\pi-p/q|\ge q^{-\nu} for all p∈Zp\in\mathbb Z and q≥Q(ν)q\ge Q(\nu). Corollary: the Flint Hills series converges, and ∑n−a∣sin⁡n∣−b\sum n^{-a}|\sin n|^{-b} converges iff a>max⁡{1,b}a>\max\{1,b\}. The bound is NOT effective (no explicit Q(ν)Q(\nu)), and it is NOT a bound of the form c/q2c/q^2: bounded partial quotients for π\pi are not claimed. The method is an interpolation…

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Theorem 1.1: μ(π)=2\mu(\pi)=2; for every ν>2\nu>2 there is Q(ν)Q(\nu) with ∣π−p/q∣≥q−ν|\pi-p/q|\ge q^{-\nu} for all p∈Zp\in\mathbb Z and q≥Q(ν)q\ge Q(\nu). Corollary: the Flint Hills series converges, and ∑n−a∣sin⁡n∣−b\sum n^{-a}|\sin n|^{-b} converges iff a>max⁡{1,b}a>\max\{1,b\}. The bound is NOT effective (no explicit Q(ν)Q(\nu)), and it is NOT a bound of the form c/q2c/q^2: bounded partial quotients for π\pi are not claimed. The method is an interpolation-determinant argument, not an improvement of the integral constructions behind earlier numerical bounds.

Theorem 1.1: μ(π)=2\mu(\pi)=2; for every ν>2\nu>2 there is Q(ν)Q(\nu) with ∣π−p/q∣≥q−ν|\pi-p/q|\ge q^{-\nu} for all p∈Zp\in\mathbb Z and q≥Q(ν)q\ge Q(\nu). Corollary: the Flint Hills series converges, and ∑n−a∣sin⁡n∣−b\sum n^{-a}|\sin n|^{-b} converges iff a>max⁡{1,b}a>\max\{1,b\}. The bound is NOT effective (no explicit Q(ν)Q(\nu)), and it is NOT a bound of the form c/q2c/q^2: bounded partial quotients for π\pi are not claimed. The method is an interpolation-determinant argument, not an improvement of the integral constructions behind earlier numerical bounds.

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The irrationality exponent of pi is 2 — Mathematical Frontier Network