English
For x, y ∈ PreTilt(O,p) and any m, p^m divides ((x·y).untiltAux m) − (x.untiltAux m)(y.untiltAux m).
Русский
Для x, y ∈ PreTilt(O,p) и любого m, p^m делит ((x·y).untiltAux m) − (x.untiltAux m)(y.untiltAux m).
LaTeX
$$$(p : O)^m \mid ((x \cdot y).untiltAux m) - (x.untiltAux m)(y.untiltAux m)$$$
Lean4
/-- The multiplication in tensor product of rings is induced by `(xᵢ) * (yᵢ) = (xᵢ * yᵢ)`
-/
def mul : (⨂[R] i, A i) →ₗ[R] (⨂[R] i, A i) →ₗ[R] (⨂[R] i, A i) :=
PiTensorProduct.piTensorHomMap₂ <| tprod R fun _ ↦ LinearMap.mul _ _