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arXiv 1706.04725cond-mat.stat-mech
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完全图上的七维临界渗流簇

Critical percolation clusters in seven dimensions and on a complete graph

Wei Huang, Pengcheng Hou, Junfeng Wang, Robert M. Ziff, Youjin Deng

摘要:

本文研究了具有周期边界条件的七维超立方晶格和有限体积$V$的完全图(CG)上的临界键渗流。我们数值证实,对于这两种情况下,规模$s$的集群的临界数密度$n(s,V)$服从标度形式$n(s,V) \sim s^{-τ} \tilde{n} (s/V^{d^*_{\rm f}})$具有相同的体积分形维数$d^*_{\rm f}=2/3$和指数$τ= 1+1/d^*_{\rm f}=5/2$。然后,我们将占据的键分为{ \em桥}键,包括{ \em分支}和{ \em连接}键,以及{ \em非桥}键;桥键是分支键,当且仅当它的删除产生至少一棵树。从渗透构型中删除分支键产生{ \em leaf-free}构型,而删除所有桥键导致{ \em bridge-free}构型。结果表明,非桥(双连接)键的分数为零$ρ_{\rm n, CG}$ $\rightarrow$ 0大CG,但收敛到一个有限的值$ ρ_{\rm n, 7D} =0.006 \, 193 \, 1(7)$的7 D超立方体。此外,我们观察到,虽然无桥维数$d^*_{\rm bf}=1/3$的CG和7 D的情况下,无叶集群的体积分形维数是不同的:$d^*_{\rm \ell f, 7D} = 0.669 (9) \approx 2/3$和$d^*_{\rm \ell f, CG} = 0. 333 7 (17) \approx 1/3$。我们还研究了无叶团簇和无桥团簇的数目和大小分布的行为。对于簇的数量,我们在CG尺度上数值地发现无叶和无桥簇的数量为$\sim \ln V$,而对于7 D,它们的尺度为$\sim V$。我们的工作表明,高维渗流集团的几何结构不能完全占其完全图对应。

英文摘要:

We study critical bond percolation on a seven-dimensional (7D) hypercubic lattice with periodic boundary conditions and on the complete graph (CG) of finite volume $V$. We numerically confirm that for both cases, the critical number density $n(s,V)$ of clusters of size $s$ obeys a scaling form $n(s,V) \sim s^{-τ} \tilde{n} (s/V^{d^*_{\rm f}})$ with identical volume fractal dimension $d^*_{\rm f}=2/3$ and exponent $τ= 1+1/d^*_{\rm f}=5/2$. We then classify occupied bonds into {\em bridge} bonds, which includes {\em branch} and {\em junction} bonds, and {\em non-bridge} bonds; a bridge bond is a branch bond if and only if its deletion produces at least one tree. Deleting branch bonds from percolation configurations produces {\em leaf-free} configurations, whereas, deleting all bridge bonds leads to {\em bridge-free} configurations. It is shown that the fraction of non-bridge (bi-connected) bonds vanishes $ρ_{\rm n, CG}$$\rightarrow$0 for large CGs, but converges to a finite value $ ρ_{\rm n, 7D} =0.006 \, 193 \, 1(7)$ for the 7D hypercube. Further, we observe that while the bridge-free dimension $d^*_{\rm bf}=1/3$ holds for both the CG and 7D cases, the volume fractal dimensions of the leaf-free clusters are different: $d^*_{\rm \ell f, 7D} = 0.669 (9) \approx 2/3$ and $d^*_{\rm \ell f, CG} = 0. 333 7 (17) \approx 1/3$. We also study the behavior of the number and the size distribution of leaf-free and bridge-free clusters. For the number of clusters, we numerically find the number of leaf-free and bridge-free clusters on the CG scale as $\sim \ln V$, while for 7D they scale as $\sim V$. Our work demonstrates that the geometric structure of high-dimensional percolation clusters cannot be fully accounted for by their complete-graph counterparts.

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