Gel'fond-type transcendence criterion with continuous growth functions
ProvedFourExp.transcendence_criterion_continuousThe transcendence criterion, for continuous growth functions.
This is FourExp.transcendence_criterion with two changes. The functions are also assumed continuous. The conditions
are required only for , not for .
Explicitly: let and . Let be continuous, strictly increasing and unbounded, and let satisfy the conditions above for . Suppose that for all there is a non-zero with coefficients at most , degree at most , and , where . Then is algebraic.
Why this form. Waldschmidt's proof (1971, §3) inverts : it defines and uses , which needs continuity. The paper notes that continuity can be assumed, since only integer values matter. That step is the accepted reduction from FourExp.transcendence_criterion, by piecewise-linear interpolation. The proof only ever uses large , so asking the conditions for loses nothing, and interpolation cannot preserve them on in general.
Intended proof. The 1971 argument, using Gel'fond's height inequality for a divisor, Gel'fond's small-irreducible-factor lemma, and the resultant bound that forces .
import Mathlib open Filter Topology
namespace FourExp
theorem transcendence_criterion_continuous
(α : ℂ) (ε : ℝ) (hε : 0 < ε)
(σ₁ σ₂ : ℝ → ℝ) (hσ₁ : StrictMono σ₁) (hσ₂ : StrictMono σ₂)
(hσ₁c : Continuous σ₁) (hσ₂c : Continuous σ₂)
(hσ₁t : Tendsto σ₁ atTop atTop) (hσ₂t : Tendsto σ₂ atTop atTop)
(a₁ a₂ : ℝ) (ha₁ : 1 ≤ a₁) (ha₂ : 1 ≤ a₂)
(h₂₁ : ∀ x : ℝ, 1 ≤ x → σ₂ x ≤ σ₁ x)
(hgrowth₁ : ∀ x : ℝ, 1 ≤ x → σ₁ (x + 1) ≤ a₁ * σ₁ x)
(hgrowth₂ : ∀ x : ℝ, 1 ≤ x → σ₂ (x + 1) ≤ a₂ * σ₂ x)
(N₀ : ℕ) (P : ℕ → Polynomial ℤ)
(hP_ne : ∀ N : ℕ, N₀ < N → P N ≠ 0)
(hP_height : ∀ N : ℕ, N₀ < N → ∀ i : ℕ, |((P N).coeff i : ℝ)| ≤ Real.exp (σ₁ N))
(hP_deg : ∀ N : ℕ, N₀ < N → ((P N).natDegree : ℝ) ≤ σ₂ N)
(hP_small : ∀ N : ℕ, N₀ < N →
‖Polynomial.aeval α (P N)‖ <
Real.exp (-(max (10 + ε) ((4 + ε) * (a₁ * a₂)) * σ₁ N * σ₂ N))) :
IsAlgebraic ℚ α := by
sorry
end FourExp