Finitely $C^\infty$-generated associative and Hopf algebras

Abstract

We introduce finitely $C^\infty$-generated algebras, which can be treated as `algebras of functions' on non-commutative $C^\infty$-differentiable spaces. Our approach uses the category of projective limits of real Banach algebras of polynomial growth. We prove the existence of some universal constructions in this and some similar categories. By analogy with holomorphically finitely generated algebras of Pirkovskii, a finitely $C^\infty$-generated algebra is defined as a quotient of a finite-rank algebra of `free $C^\infty$-functions'. The latter notion was introduced by the author in a previous article, where a structure theorem for algebras of `free $C^\infty$-functions' was announced and proved in dimension at most $2$. Here this theorem is proved in full generality. The central result asserts that the projective tensor product of a finite tuple of finitely $C^\infty$-generated algebras is finitely $C^\infty$-generated. In particular, this makes it natural to consider finitely $C^\infty$-generated topological Hopf algebras. Furthermore, a construction called `envelope' provides a functor from the category of affine real Hopf algebras to the category of finitely $C^\infty$-generated Hopf algebras.