English
There is a noncomputable algebra equivalence between the power algebra and the free tensor algebra over the same data.
Русский
Существует необязательно вычисляемое эквивалентность алгебр между пауэр-алгеброй и свободной тензорной алгеброй над теми же данными.
LaTeX
$$$\\text{powerAlgebraEquivFreeTensorAlgebra} : \\text{PowerAlgebra } R A \\simeq_R \\text{FreeTensorAlgebra } R A$$$
Lean4
/-- The direct sum of tensor powers of a direct sum of `R`-algebras,
before taking the quotient by the free product relation -/
abbrev PowerAlgebra :=
⨁ (n : ℕ), TensorPower R n (⨁ i, A i)