English
For v,w: Fin n → α, the product circulant v · circulant w equals circulant of circulant v ·ᵥ w.
Русский
Для v, w: Fin n → α выполняется circulant v · circulant w = circulant( circulant v ·ᵥ w ).
LaTeX
$$$\\operatorname{circulant}(v) \\cdot \\operatorname{circulant}(w) = \\operatorname{circulant}(\\operatorname{circulant}(v) *\\!\\!\\mathrm{vec} w)$$$
Lean4
theorem circulant_mul [NonUnitalNonAssocSemiring α] :
∀ {n} (v w : Fin n → α), circulant v * circulant w = circulant (circulant v *ᵥ w)
| 0 => by simp [eq_iff_true_of_subsingleton]
| _ + 1 => Matrix.circulant_mul