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7 votes
2 answers
871 views

Amenable action intuition

Let $\Gamma$ be a discrete group and $A$ be a $C^*$-algebra. Consider an action $\alpha: \Gamma \to \operatorname{Aut}(A)$. There is a notion of amenability for such an action (see e.g. Brown and ...
Andromeda's user avatar
  • 175
5 votes
1 answer
237 views

Characterization of exact groups via the existence of amenable actions on unital C*-algebras, part 2

In this recent MOF question I asked whether exact groups could be characterized via the existence of amenable actions on unital C*-algebras. The answer, provided by Caleb Eckhardt in a comment, was ...
Ruy's user avatar
  • 2,263
10 votes
2 answers
1k views

Kazhdan's property (T) vs. residual finiteness

I have asked this question already on mathstackexchange but got no answer (see https://math.stackexchange.com/questions/1795795/kazhdans-property-t-vs-residual-finiteness) and it was suggested that I ...
M.U.'s user avatar
  • 721