English
Meromorphic functions have normal form on a codiscrete set inside U whenever they are meromorphic on U.
Русский
У функции мероморфна в нормальной форме на кодискретном подмножестве внутри U, если она мероморфна на U.
LaTeX
$$$\text{MeromorphicNFOn } f U$ implies $\{x : a\;|\; \text{MeromorphicNFAt } f x\} \in \text{Filter.codiscreteWithin } U$$$
Lean4
/-- Meromorphic functions have normal form outside of a discrete subset in the domain of
meromorphicity. -/
theorem meromorphicNFAt_mem_codiscreteWithin {U : Set 𝕜} (hf : MeromorphicOn f U) :
{x | MeromorphicNFAt f x} ∈ Filter.codiscreteWithin U :=
by
filter_upwards [hf.analyticAt_mem_codiscreteWithin] with _ ha
exact ha.meromorphicNFAt