2 problems

The $C^k$-map versus ring-homomorphism conjecture. The following statements are equivalent: (1) $\varphi^{\sharp}$ is a ring-homomorphism over ${\Bbb R}\hookrightarrow{\Bbb C}$; (2…

Let $A_n$ be the $n$-th Weyl algebra over the field $F$, let $\varphi:A_n\to A_n$ be a homomorphism, and write $\operatorname{GKdim}$ for Gelfand–Kirillov dimension. The preceding…