Groups, Geometry, and Dynamics ( IF 0.6 ) Pub Date : 2020-10-13 , DOI: 10.4171/ggd/567 Christophe Garban 1
Our main result is that for any bounded degree graph $X$, the action $W(X)\curvearrowright X$ is diffuse-extensively amenable if and only if $X$ is recurrent. Our proof is based on the construction of suitable stochastic processes $(\tau_t)_{t\geq 0}$ on $W(X)\, <\, \mathfrak{S}(X)$ whose inverted orbits $$\bar O_t(x_0) = \{x\in X\colon \text{there exists } s\leq t \text{\ s.t.\ } \tau_s(x)=x_0\} = \bigcup_{0\leq s \leq t} \tau_s^{-1}(\{x_0\})$$ are exponentially unlikely to be sub-linear when $X$ is transient.
This result leads us to conjecture that the action $W(\mathbb Z^d)\curvearrowright \mathbb Z^d$ is not extensively amenable when $d\geq 3$ and that a different route towards the (non-?)amenability of the IET group may be needed.
中文翻译:
排除过程的反转轨道,区间交换的扩散性-可及性和(非-)可容性
最近的突破性工作[9,11,12]建立了新类别的群体的适应性,导致了以下问题:$ W(\ mathbb Z ^ d)\ curvearrowright \ mathbb Z ^ d $动作是否可以广泛适应?(其中$ W(\ mathbb Z ^ d)$是波动范围$ \ sigma \冒号\ mathbb Z ^ d \到\ mathbb Z ^ d $的波动组)。这等效于询问动作$(\ mathbb Z / 2 \ mathbb Z)^ {(\ mathbb Z ^ d)} \ rtimes W(\ mathbb Z ^ d)\ curvearrowright(\ mathbb Z / 2 \ mathbb Z )^ {(\ mathbb Z ^ d)} $是可以接受的。$ d = 1 $和$ d = 2 $分别在[9,11]中结算。到[12],对这个问题的肯定回答将意味着IET小组的能力。在这项工作中,我们通过引入自然加强的概念来部分回答这个问题。广泛可取性,我们称为扩散广泛可取性。
我们的主要结果是,对于任何有界度图$ X $,当且仅当$ X $经常出现时,动作$ W(X)\ curvearrowright X $才能广泛地扩散。我们的证明是基于构造合适的随机过程$(\ tau_t)_ {t \ geq 0} $在$ W(X)\,<\,\ mathfrak {S}(X)$上的,其倒转轨道$$ \ bar O_t(x_0)= \ {x \ in X \冒号\ text {存在} s \ leq t \ text {\ st \} \ tau_s(x)= x_0 \} = \ bigcup_ {0 \ leq s \ leq t} \ tau_s ^ {-1}(\ {x_0 \})$$在$ X $是瞬态时不太可能是次线性的。
此结果使我们推测,当$ d \ geq 3 $时,动作$ W(\ mathbb Z ^ d)\ curvearrowright \ mathbb Z ^ d $不能广泛接受,并且朝向(non-?)可能需要IET组的成员。