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4 votes

central extensions of Diff(S^1) and of the semigroup of annuli

Let me give a method for answering the problem. I haven't yet done the relevant integral to get an actual answer. In the setting you originally laid out for $\mathcal{A}$, actual diffeomorphisms are …
Dylan Thurston's user avatar
6 votes

central extensions of Diff(S^1) and of the semigroup of annuli

There's a more geometrically natural description of a $\mathbb{Z}$-central extension in both cases. For $\operatorname{Diff}(S^1)$, the central extension are diffeomorphisms $f: \mathbb{R} \to \mathb …
Dylan Thurston's user avatar