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

10 events

when toggle format	what		by	license	comment
Sep 2, 2016 at 23:16	comment	added	André Henriques		The requirement that the boundary parametrizations be constant-speed geodesics mean that one can glue the Riemannian metrics. Thus, the product of $(g,a)$ with $(g',a')$ is $(g \cup g',a+a')$.
Sep 1, 2016 at 19:33	comment	added	Dylan Thurston		Just coming back to this question after years. What's the multiplication on $\widetilde{\mathcal{A}}$?
Feb 4, 2014 at 6:08	history	edited	André Henriques	CC BY-SA 3.0	deleted 3 characters in body
Nov 26, 2011 at 14:11	history	edited	André Henriques	CC BY-SA 3.0	edited body
Apr 17, 2011 at 13:00	answer	added	Dylan Thurston		timeline score: 4
Apr 14, 2011 at 18:42	answer	added	David Ben-Zvi		timeline score: 8
Apr 14, 2011 at 10:12	comment	added	Dylan Thurston		One reason these look different is that the "subgroup" $\widetilde{\operatorname{Diff}}(S^1)$ looks a little odd in $\widetilde{\mathcal{A}}$. In particular, you'd like to take a thin annulus with boundaries parametrized in two different ways. But you require that the boundary be parametrized by constant-speed geodesics, which requires you to blow up the metric near the boundary by a conformal factor $\phi$ depending on the speed of the parametrization.
Apr 13, 2011 at 23:28	answer	added	Dylan Thurston		timeline score: 6
Apr 13, 2011 at 23:00	history	edited	André Henriques	CC BY-SA 3.0	added 2 characters in body; edited title
Apr 13, 2011 at 22:47	history	asked	André Henriques	CC BY-SA 3.0