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If a non-real logarithm λ and its conjugate are algebraic over one ring ℚ[x], e^{|λ|} is transcendental

Proved
DiazModulus.exp_abs_transcendental_of_isAlgebraic_adjoin

by carlok · Sep 25, 2026 · Mathlib 0df444a (Lean v4.33.1)

diaz-modulus-leannumber-theorytranscendence

Let λ∈C\lambda \in \mathbb{C}λ∈C with eλe^{\lambda}eλ algebraic and Im⁡λ≠0\operatorname{Im}\lambda \neq 0Imλ=0. Suppose that λ\lambdaλ and λˉ\bar\lambdaλˉ are both algebraic over the ring Q[x]\mathbb{Q}[x]Q[x], for some x∈Cx \in \mathbb{C}x∈C. Then

e∣λ∣e^{|\lambda|}e∣λ∣

is transcendental.

The hypothesis puts λ\lambdaλ and λˉ\bar\lambdaλˉ in an algebra of transcendence degree at most one, which is what four exponentials in transcendence degree one needs. With x=λx = \lambdax=λ this is DiazModulus.exp_abs_transcendental_of_conj_algebraic. With λ=log⁡2+iπ\lambda = \log 2 + i\piλ=log2+iπ and x=iπx = i\pix=iπ it gives DiazModulus.exp_abs_log_two_add_i_pi_transcendental.

Preamble
import Mathlib
Formal statement
open ComplexConjugate

namespace DiazModulus

theorem exp_abs_transcendental_of_isAlgebraic_adjoin (lam x : ℂ)
    (hlam : IsAlgebraic ℚ (Complex.exp lam)) (him : lam.im ≠ 0)
    (hl : IsAlgebraic ↥(Algebra.adjoin ℚ ({x} : Set ℂ)) lam)
    (hc : IsAlgebraic ↥(Algebra.adjoin ℚ ({x} : Set ℂ)) (conj lam)) :
    Transcendental ℚ (Complex.exp ((‖lam‖ : ℝ) : ℂ)) := by
  sorry

end DiazModulus
Source
Known in substance: it is the argument behind G. Diaz, La conjecture des quatre exponentielles et les conjectures de D. Bertrand sur la fonction modulaire, J. Théor. Nombres Bordeaux 9 (1997), 229–245, Proposition 2, and D. Roy and M. Waldschmidt, Approximation diophantienne et indépendance algébrique de logarithmes, Ann. Sci. École Norm. Sup. (4) 30 (1997), 753–796, Corollaire 7.4. Formal proof: Diaz modulus mission, 25 September 2026 (C. Perassi).

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