English
A quantitative version: the absolute difference of characteristics is bounded by a constant depending on f, independent of R.
Русский
Количественная версия: абсолютная разность характеристик ограничена константой, зависящей от f и не зависящей от R.
LaTeX
$$$|\text{characteristic}(f) - \text{characteristic}(f^{-1})| \le C$ for some constant C$$
Lean4
/-- First part of the First Main Theorem, quantitative version: If `f` is meromorphic on the complex
plane, then the difference between the characteristic functions of `f` and `f⁻¹` is bounded by an
explicit constant.
-/
theorem characteristic_sub_characteristic_inv_le (hf : MeromorphicOn f Set.univ) :
|characteristic f ⊤ R - characteristic f⁻¹ ⊤ R| ≤ max |log ‖f 0‖| |log ‖meromorphicTrailingCoeffAt f 0‖| :=
by
by_cases h : R = 0
· simp [h, characteristic_sub_characteristic_inv_at_zero hf]
· simp [characteristic_sub_characteristic_inv_of_ne_zero hf h]