English
Locally finite of supports is equivalent to locally finite of their multiplicative supports.
Русский
Локальная конечность опор эквивалентна локальной конечности их мультиподдержек.
LaTeX
$$$\operatorname{LocallyFinite}(i \mapsto \operatorname{mulSupport}(f_i)) \iff \operatorname{LocallyFinite}(i \mapsto \operatorname{mulTSupport}(f_i)).$$$
Lean4
/-- If `a` and `b` commute and `b` is topologically nilpotent,
then `a * b` is topologically nilpotent. -/
theorem mul_left_of_commute [IsLinearTopology R R] {a b : R} (hb : IsTopologicallyNilpotent b) (hab : Commute a b) :
IsTopologicallyNilpotent (a * b) :=
by
simp_rw [IsTopologicallyNilpotent, hab.mul_pow]
exact IsLinearTopology.tendsto_mul_zero_of_right _ _ hb