English
Analogous bottom basis: the bottom neighborhood basis is derived from the dual of the top basis.
Русский
Аналогичный нижний базис: базис окрестностей нуля выводится через двойственный верхний базис.
LaTeX
$$$𝓝(\\bot)\\text{ has basis from the dual construction.}$$$
Lean4
theorem nhds_bot_basis [TopologicalSpace α] [LinearOrder α] [OrderBot α] [OrderTopology α] [Nontrivial α] :
(𝓝 ⊥).HasBasis (fun a : α => ⊥ < a) fun a : α => Iio a :=
nhds_top_basis (α := αᵒᵈ)