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arXiv 0909.1893math.PRmath.GR
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群的自由积上随机游动渐近性的相变

Phase Transitions for Random Walk Asymptotics on Free Products of Groups

Elisabetta Candellero, Lorenz A. Gilch

摘要:

假设我们给定一个具有不可约随机游动的群$Γ_1,...,Γ_m$.因此,我们假设相应的格林函数在其收敛半径的展开式只包含对数或代数项作为奇异项,直到足够大的顺序(除了一些退化的情况)。我们考虑自由积{ $Γ_1 \ast ... \astΓ_m$ }上的瞬态随机游动,并给出相应的$n$步返回概率的可能渐近行为的完整分类。它们要么从自由因子$Γ_i$之一继承$\varrho^{nδ} n^{-λ_i} \log^{κ_i}n$形式的定律,要么服从$\varrho^{nδ} n^{-3/2}$ -定律,其中$\varrho<1$是相应的谱半径,$δ$是随机游动的周期。此外,我们确定的情况下最近邻随机游动的形式$\Z^{d_1}\ast ... \ast \Z^{d_m}$的自由积的渐近行为的全范围。此外,我们描述的情况下,$Γ_1\astΓ_2$的非指数型$n^{-λ_i}\log^{κ_i}n$的可能的相变。

英文摘要:

Suppose we are given finitely generated groups $Γ_1,...,Γ_m$ equipped with irreducible random walks. Thereby we assume that the expansions of the corresponding Green functions at their radii of convergence contain only logarithmic or algebraic terms as singular terms up to sufficiently large order (except for some degenerate cases). We consider transient random walks on the free product {$Γ_1 \ast ... \astΓ_m$} and give a complete classification of the possible asymptotic behaviour of the corresponding $n$-step return probabilities. They either inherit a law of the form $\varrho^{nδ} n^{-λ_i} \log^{κ_i}n$ from one of the free factors $Γ_i$ or obey a $\varrho^{nδ} n^{-3/2}$-law, where $\varrho<1$ is the corresponding spectral radius and $δ$ is the period of the random walk. In addition, we determine the full range of the asymptotic behaviour in the case of nearest neighbour random walks on free products of the form $\Z^{d_1}\ast ... \ast \Z^{d_m}$. Moreover, we characterize the possible phase transitions of the non-exponential types $n^{-λ_i}\log^{κ_i}n$ in the case $Γ_1\astΓ_2$.

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