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Oct 20, 2015 at 19:02 comment added Yemon Choi BTW I hope my comment wasn't perceived as denigrating the amenable iff nuclear results, which I hold in very high regard. It's just that sometimes they are used when there are easier, and more informative, approaches for particular examples one is considering
Oct 20, 2015 at 18:59 comment added Yemon Choi @NikWeaver Who says I have to mention pink elephants? Oh, damn :)
Oct 20, 2015 at 18:51 comment added Nik Weaver @YemonChoi: and yet you mentioned them ...
Oct 20, 2015 at 15:59 comment added Yemon Choi Just because it is something I always go on about, I shall do so here :) ... Lance proved that $G$ is amenable iff ${\rm C}_r^*(G)$ is nuclear, using one of the original definitions of nuclearity. Then Bunce proved, without requiring any of Lance's results, that if ${\rm C}_r^*(G)$ is amenable as a Banach algebra and $G$ is discrete, then $\ell^\infty(G)$ has a (left or right or two-sided) invariant mean, so $G$ is amenable. I mention these in order to emphasize that non-nuclearity & non-amenability of ${\rm C}_r^*(F_2)$ can be discussed without mentioning the names of Connes or Haagerup :)
Oct 20, 2015 at 15:50 vote accept Albert harold
Oct 20, 2015 at 15:33 comment added Ulrich Pennig The only link I can find for Powers' paper is behind a paywall, sorry.
Oct 20, 2015 at 15:33 history answered Ulrich Pennig CC BY-SA 3.0