English
If J ≃ I is an equivalence, then OrthogonalIdempotents (e ∘ i) is equivalent to OrthogonalIdempotents e.
Русский
Если J эквивалентно I, то OrthogonalIdempotents (e ∘ i) эквивалентно OrthogonalIdempotents e.
LaTeX
$$OrthogonalIdempotents (e ∘ i) ↔ OrthogonalIdempotents e$$
Lean4
theorem equiv {J} [Fintype J] (i : J ≃ I) : CompleteOrthogonalIdempotents (e ∘ i) ↔ CompleteOrthogonalIdempotents e :=
by
simp only [completeOrthogonalIdempotents_iff, OrthogonalIdempotents.equiv, Function.comp_apply,
Fintype.sum_equiv i _ e (fun _ ↦ rfl)]