Timeline for Sums of unitaries with small norm in full group $C^*$-algebras

8 events

when toggle format	what		by	license	comment
May 12, 2012 at 18:14	vote	accept	Mike Jury
May 12, 2012 at 11:32	answer	added	Mikael de la Salle		timeline score: 6
May 12, 2012 at 7:13	comment	added	Mikael de la Salle		I think that there is a rather simple iff condition for $\alpha(S)=1$~: if $S=\{g_1,g_2,\dots,g_n\}$, $\alpha(S)=1$ iff $g_1^{-1} g_2,\dots g_1^{-1} g_n$ generate a free abelian subgroup in the abelianization of $G$. I do not have time right now to write a proof, but if you are interested I can do it when I come back.
May 12, 2012 at 5:01	vote	accept	Mike Jury
May 12, 2012 at 18:14
May 12, 2012 at 3:35	history	edited	Mike Jury	CC BY-SA 3.0	added 384 characters in body
May 12, 2012 at 3:07	answer	added	Nik Weaver		timeline score: 4
May 12, 2012 at 1:37	answer	added	Nik Weaver		timeline score: 2
May 12, 2012 at 1:24	history	asked	Mike Jury	CC BY-SA 3.0