关于Avez的一个定理
On a theorem of Avez
摘要:
对于有限生成群$G$上的每个对称、非周期概率测度$μ$,我们定义一个由群元素$g$组成的子集$A_μ$,其中比率${μ^{\ast n}(g)}/{μ^{\ast n}(e)}$的极限趋于$1$。证明了$A_μ$是一个子群,是顺从的,包含每个有限正规子群,$G=A_μ$当且仅当$G$是顺从的.对于非顺从群,我们证明了$A_μ$并不总是一个正规子群,并且可以依赖于测量。我们用公式表示了$A_μ$与顺从自由基的关系。
英文摘要:
For each symmetric, aperiodic probability measure $μ$ on a finitely generated group $G$, we define a subset $A_μ$ consisting of group elements $g$ for which the limit of the ratio ${μ^{\ast n}(g)}/{μ^{\ast n}(e)}$ tends to $1$. We prove that $A_μ$ is a subgroup, is amenable, contains every finite normal subgroup, and $G=A_μ$ if and only if $G$ is amenable. For non-amenable groups we show that $A_μ$ is not always a normal subgroup, and can depend on the measure. We formulate some conjectures relating $A_μ$ to the amenable radical.
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