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 Mar 24 revised approximate vanishing in Pontryagin dual added 23 characters in body Mar 24 revised approximate vanishing in Pontryagin dual Add more rks Mar 24 accepted when a crossed product group is inner amenable Mar 24 asked approximate vanishing in Pontryagin dual Mar 4 awarded Custodian Feb 17 answered when a crossed product group is inner amenable Feb 16 revised when a crossed product group is inner amenable Add one more condition Feb 16 asked when a crossed product group is inner amenable Jan 27 comment When two projections in a C*-algebra are “almost” Murray-von Neumann equivalent, they are equivalent Intuitively, maybe we can first show that when $aa^*$ is close to $p$, then the range projection of $aa^*$, denote it by $r_1$, is close to $p$, maybe the assumption is strong enough to imply $||r_1-p||<1$, so they are unitary equivalent, do the same thing for $q$, note that $r_1, r_2$ are unitary equivalent. Jan 26 accepted find a special group Jan 26 asked find a special group Jan 25 comment one end group with positve first Betti number$\beta^{(2)}_1(G)>0$ Thanks again! It is good to know that... Jan 24 comment one end group with positve first Betti number$\beta^{(2)}_1(G)>0$ Thanks, to see the surface groups have one end, if my understanding is right, just look at the Cayley group(some tiling of the plane); is there any way to see directly that the surface groups could not be of the form predicted by the Stalling theorem? Btw, how to see in (2), $B^1$ is not closed?... Jan 24 accepted one end group with positve first Betti number$\beta^{(2)}_1(G)>0$ Jan 23 asked one end group with positve first Betti number$\beta^{(2)}_1(G)>0$ Jan 22 accepted Extending a measurable map $f: G \to \mathbb{R}/\mathbb{Z}$ to a continuous group homomorphism Jan 17 accepted Any infinite property (T) subgroup of $Aut(F_n)$? Jan 16 asked Any infinite property (T) subgroup of $Aut(F_n)$? Dec 21 awarded Constituent Dec 11 awarded Caucus