English
Locally finite of multiplicative supports yields a Finset controlling the supports near x.
Русский
Локальная конечность мультиподдержек дает конечный набор индексов, управляющий поддержками рядом с x.
LaTeX
$$$\exists \text{is} : \Finset ι,\ \exists n \in 𝓝 x,\ n \subseteq \bigcap_{i\in \text{is}} U_i \land \forall z \in n,\ \operatorname{mulSupport}(\lambda i. f_i(z)) \subseteq \text{is}.$$$
Lean4
/-- If `a` and `b` commute and `a` is topologically nilpotent,
then `a * b` is topologically nilpotent. -/
theorem mul_right_of_commute [IsLinearTopology Rᵐᵒᵖ R] {a b : R} (ha : IsTopologicallyNilpotent a) (hab : Commute a b) :
IsTopologicallyNilpotent (a * b) :=
by
simp_rw [IsTopologicallyNilpotent, hab.mul_pow]
exact IsLinearTopology.tendsto_mul_zero_of_left _ _ ha