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arXiv 1003.2370math.GR
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相对端点、l^2不变量与性质(T)

Relative Ends, l^2 Invariants and Property (T)

Aditi Kar, Graham A. Niblo

摘要:

对单端群H<G建立了一个分裂定理,使得\tilde{e}(G;H)> 2,且H的几乎反常闭包是G的一个真子群.这给出了具有非平凡第一个l^2贝蒂数(β^2_1(G))的群G的分裂定理。证明了对H < G满足β^2_1(G)> β^2_1(H)的Kropholler猜想.我们还证明了每个包含一个具有性质(T)的Poincare对偶(PD^n)群H的n维Poincare对偶(PD^n)群在一个与H可分解的子群上分裂.

英文摘要:

We establish a splitting theorem for one-ended groups H<G such that \tilde{e}(G;H)> 2 and the almost malnormal closure of H is a proper subgroup of G. This yields splitting theorems for groups G with non-trivial first l^2 Betti number (β^2_1(G)). We verify the Kropholler Conjecture for pairs H < G satisfying β^2_1(G) > β^2_1(H). We also prove that every n-dimensional Poincare duality (PD^n) group containing a PD^(n-1) group H with property (T) splits over a subgroup commensurable with H.

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