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Strong four exponentials implies that no algebraic multiple of 1/(iπ)1/(i\pi)1/(iπ) is a logarithm

Proved
DiazModulus.recip_pi_not_log_of_sfe

by carlok · Sep 8, 2026 · Mathlib 0df444a (Lean v4.33.1)

four-exponentialslogarithmsnumber-theorytranscendence

The strong four exponentials conjecture implies DiazModulus.recip_pi_not_log: that no non-zero algebraic γ\gammaγ has γ/(iπ)\gamma/(i\pi)γ/(iπ) a logarithm of an algebraic number.

The configuration. Write λ=γ/(iπ)\lambda = \gamma/(i\pi)λ=γ/(iπ) and suppose eλe^{\lambda}eλ is algebraic. Apply the strong four exponentials conjecture to

x=(1, λ),y=(1, iπ).x = (1,\ \lambda), \qquad y = (1,\ i\pi).x=(1, λ),y=(1, iπ).

The four products are 111, iπi\piiπ, λ\lambdaλ, and λ⋅iπ=γ\lambda \cdot i\pi = \gammaλ⋅iπ=γ. All four lie in L~\widetilde{\mathcal{L}}L: the first by definition; iπi\piiπ because eiπ=−1e^{i\pi} = -1eiπ=−1 is algebraic; λ\lambdaλ by the assumption being contradicted; and γ\gammaγ because it is algebraic, and L~\widetilde{\mathcal{L}}L is a Q‾\overline{\mathbb{Q}}Q​-vector space containing 111. That contradicts the conjecture, provided both rows are Q‾\overline{\mathbb{Q}}Q​-linearly independent.

What supplies the independence, and it is not π\piπ-transcendence. Both (1,λ)(1,\lambda)(1,λ) and (1,iπ)(1,i\pi)(1,iπ) are independent as soon as λ\lambdaλ and iπi\piiπ are transcendental, and Hermite–Lindemann alone gives both — no separate input on the transcendence of π\piπ is needed. For iπi\piiπ: it is non-zero, and if it were algebraic then eiπ=−1e^{i\pi} = -1eiπ=−1 would be transcendental. For λ\lambdaλ: it is non-zero since γ≠0\gamma \neq 0γ=0, and if it were algebraic then eλe^{\lambda}eλ would be transcendental, against the assumption. Hermite–Lindemann is available on this mission as the Proved node DiazModulus.hermite_lindemann_holds, so it is discharged rather than carried, and the strong four exponentials conjecture is the only hypothesis this node retains.

What it is for. DiazModulus.recip_pi_not_log is open and two further open leaves of Diaz's modulus conjecture reduce to it. This node records exactly what strength would settle it, and pins that strength to a named conjecture rather than to a vague appeal. It does not make the parent easier: the strong four exponentials conjecture is open, and is itself the assumption the whole modulus conjecture currently rests on.

Preamble
import Definitions.Def_DiazModulus

open Complex ComplexConjugate
Formal statement
namespace DiazModulus
theorem recip_pi_not_log_of_sfe :
    StrongFourExponentials →
      ∀ γ : ℂ, IsAlgebraic ℚ γ → γ ≠ 0 →
        ¬ IsAlgebraic ℚ (Complex.exp (γ / (((Real.pi : ℝ) : ℂ) * Complex.I))) := by sorry
end DiazModulus
Source
The four-exponentials configuration x = (1, gamma/(i*pi)), y = (1, i*pi). Independence of both rows follows from Hermite-Lindemann alone; see Waldschmidt, Diophantine Approximation on Linear Algebraic Groups, Ch. 11 for the strong four exponentials conjecture.

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