arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1507.08871math.DSmath.MGmath.PR
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共形迭代函数系中测度的重叠函数

Overlap functions for measures in conformal iterated function systems

Eugen Mihailescu, Mariusz Urbanski

摘要:

研究了具有任意重叠的共形迭代函数系统(IFS)$\mathcal S = \{ϕ_i\}_{i \in I}$,以及极限集$Λ$上的测度$μ$,极限集$Λ$是平衡测度$\hat μ$关于提升映射$Φ$在$Σ_I^+ \times Λ$上的投影.未假定任何类型的开集条件。我们介绍了这样一个措施$\hat μ$的重叠功能和重叠数的概念,$\mathcal S$,特别是(拓扑)重叠数$o(\mathcal S)$的概念。这些概念考虑了极限集中点之间的$n$链。我们证明了$o(\mathcal S, \hat μ)$与$\hat μ$关于提升$Φ$的条件熵有关。各种类型的投影$Λ$不变的措施进行了研究。利用压力函数和$o(\mathcal S, \hat μ)$得到了$μ$在$Λ$上的Hausdorff维数$HD(μ)$的上估计.特别是,这适用于$Σ_I^+$上的伯努利测度的预测。接下来,我们将结果应用于$λ\in (\frac 12, 1)$的伯努利卷积$ν_λ$,其对应于通过以相等的概率组成具有重叠$\mathcal S_λ$的IFS的收缩来确定的自相似测度。证明了对所有的$λ\in (\frac 12, 1)$,$HD(ν_λ)$与重叠数$o(\mathcal S_λ)$之间存在关系.数$o(\mathcal S_λ)$近似于$Σ_2^+$上关于均匀伯努利测度$ν_{(\frac 12, \frac 12)}$的积分。我们还估计了某些$λ$值的$o(\mathcal S_λ)$。

英文摘要:

We study conformal iterated function systems (IFS) $\mathcal S = \{ϕ_i\}_{i \in I}$ with arbitrary overlaps, and measures $μ$ on limit sets $Λ$, which are projections of equilibrium measures $\hat μ$ with respect to a certain lift map $Φ$ on $Σ_I^+ \times Λ$. No type of Open Set Condition is assumed. We introduce a notion of overlap function and overlap number for such a measure $\hat μ$ with respect to $\mathcal S$; and, in particular a notion of (topological) overlap number $o(\mathcal S)$. These notions take in consideration the $n$-chains between points in the limit set. We prove that $o(\mathcal S, \hat μ)$ is related to a conditional entropy of $\hat μ$ with respect to the lift $Φ$. Various types of projections to $Λ$ of invariant measures are studied. We obtain upper estimates for the Hausdorff dimension $HD(μ)$ of $μ$ on $Λ$, by using pressure functions and $o(\mathcal S, \hat μ)$. In particular, this applies to projections of Bernoulli measures on $Σ_I^+$. Next, we apply the results to Bernoulli convolutions $ν_λ$ for $λ\in (\frac 12, 1)$, which correspond to self-similar measures determined by composing, with equal probabilities, the contractions of an IFS with overlaps $\mathcal S_λ$. We prove that for all $λ\in (\frac 12, 1)$, there exists a relation between $HD(ν_λ)$ and the overlap number $o(\mathcal S_λ)$. The number $o(\mathcal S_λ)$ is approximated with integrals on $Σ_2^+$ with respect to the uniform Bernoulli measure $ν_{(\frac 12, \frac 12)}$. We also estimate $o(\mathcal S_λ)$ for certain values of $λ$.

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