English
The space of functions from β to a family C(b) of groups, with the product topology, forms a topological group under pointwise multiplication.
Русский
Пространство функций β → C(b) с произведением топологий образует топологическую группу под поконой покомпонентной умножением.
LaTeX
$$$IsTopologicalGroup\left(\prod_{b\in \beta} C(b)\right)$$$
Lean4
@[to_additive]
instance topologicalGroup {C : β → Type*} [∀ b, TopologicalSpace (C b)] [∀ b, Group (C b)]
[∀ b, IsTopologicalGroup (C b)] : IsTopologicalGroup (∀ b, C b) where
continuous_inv := continuous_pi fun i => (continuous_apply i).inv