English
For any finite set s in a normed space, if s is contained in the ball of radius 2 and pairwise distances are at least 1, then |s| ≤ multiplicity(E).
Русский
Для любого конечного множества s в нормированном пространстве, если ∥c∥ ≤ 2 для всех c ∈ s и расстояния между различными элементами не менее 1, то |s| ≤ multiplicity(E).
LaTeX
$$$$s.card \\le Besicovitch.multiplicity(E)$$$$
Lean4
theorem card_le_multiplicity {s : Finset E} (hs : ∀ c ∈ s, ‖c‖ ≤ 2) (h's : ∀ c ∈ s, ∀ d ∈ s, c ≠ d → 1 ≤ ‖c - d‖) :
s.card ≤ multiplicity E := by
apply le_csSup
· refine ⟨5 ^ finrank ℝ E, ?_⟩
rintro _ ⟨s, ⟨rfl, h⟩⟩
exact Besicovitch.card_le_of_separated s h.1 h.2
· simp only [mem_setOf_eq, Ne]
exact ⟨s, rfl, hs, h's⟩