Universality of the annulus central extension for diffeological semigroups

Let $\operatorname{Ann}$ be the annulus semigroup and let

$$0\to\mathbb{C}\times\mathbb{Z}\to\operatorname{A\widetilde{\!\!\phantom{i}n\phantom{i}\!\!}n}\to\operatorname{Ann}\to0$$

be the stated central extension. Diffeological universality conjecture. This extension is a universal central extension in the category of diffeological semigroups over manifolds with corners. The paper proves that the extension is a central extension of real diffeological semigroups, but leaves its universality open.