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The irrationality measure of π is at most 7.103205334138

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PiIrrationality.zeilberger_zudilin_bound

by xuanji · Oct 3, 2026 · Mathlib 0df444a (Lean v4.33.1)

diophantine-approximationirrationalitynumber-theorypi

The irrationality measure of π\piπ is at most 7.1032053341387.1032053341387.103205334138. For every real ε>0\varepsilon>0ε>0, there is a natural threshold QQQ, uniform in the integer numerator ppp and positive natural denominator q≥Qq\ge Qq≥Q, such that 1/q7.103205334138+ε<∣π−p/q∣1/q^{7.103205334138+\varepsilon}<|\pi-p/q|1/q7.103205334138+ε<∣π−p/q∣.

Preamble
import Definitions.Def_PiIrrationality_UpperBound
Formal statement
theorem PiIrrationality.zeilberger_zudilin_bound :
    PiIrrationality.UpperBound (7.103205334138 : ℝ) := by
  sorry
Source
D. Zeilberger, W. Zudilin, *The irrationality measure of π\piπ is at most 7.103205334137…7.103205334137\ldots7.103205334137…*, Moscow J. Combin. Number Theory 9 (2020), no. 4, 407–419. https://arxiv.org/abs/1912.06345
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What the Lean code literally says, in plain math · claude-opus-5-5

Theorem PiIrrationality.zeilberger_zudilin_bound asserts that the real number B=7.103205334138B = 7.103205334138B=7.103205334138 satisfies the property PiIrrationality.UpperBound. The decimal literal is interpreted as the exact rational real number 71032053341381012\frac{7103205334138}{10^{12}}10127103205334138​ =3551602667069500000000000= \frac{3551602667069}{500000000000}=5000000000003551602667069​ (no floating-point rounding). Unfolding the definition, the statement is:

For every real number ε>0\varepsilon > 0ε>0 there exists a natural number Q∈N={0,1,2,… }Q \in \mathbb{N} = \{0,1,2,\dots\}Q∈N={0,1,2,…} such that for every integer p∈Zp \in \mathbb{Z}p∈Z and every natural number qqq with q>0q > 0q>0 and q≥Qq \ge Qq≥Q,

1q7.103205334138+ε  <  ∣π−pq∣.\frac{1}{q^{7.103205334138 + \varepsilon}} \;<\; \left|\pi - \frac{p}{q}\right|.q7.103205334138+ε1​<​π−qp​​.

Here π\piπ is the real constant Real.pi, ppp and qqq are cast to real numbers, p/qp/qp/q is real division (well-defined since q≥1q \ge 1q≥1), ∣⋅∣|\cdot|∣⋅∣ is the real absolute value, and the power q7.103205334138+εq^{7.103205334138 + \varepsilon}q7.103205334138+ε is the real-exponent power function Real.rpow (for the positive base qqq this is exp⁡((7.103205334138+ε)ln⁡q)\exp((7.103205334138 + \varepsilon)\ln q)exp((7.103205334138+ε)lnq), the usual real power). The inequality is strict. The threshold QQQ may depend on ε\varepsilonε but not on ppp or qqq; it is allowed to be 000 or 111, in which case the only constraint on qqq is q≥1q \ge 1q≥1. The integer ppp is unrestricted (any sign, including 000), and there is no requirement that ppp and qqq be coprime or that p/qp/qp/q be close to π\piπ; for fractions far from π\piπ the inequality is easy, so the content concerns approximations near π\piπ. No other hypotheses, implicit arguments, or typeclass assumptions appear.

Human review
  • Endorsed by Shuze Chen · Oct 4, 2026

    Confirmed by the moderator at approval.

  • Endorsed by xuanji · Oct 4, 2026

    Confirmed by the mission captain (proposal self-audit).

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