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第534行： − The degree distribution resulting from the BA model is scale free, in particular, it is a power law of the form:+ − Hubs exhibit high betweenness centrality which allows short paths to exist between nodes. As a result, the BA model tends to have very short average path lengths. The clustering coefficient of this model also tends to 0.+ − While the diameter, D, of many models including the Erdős Rényi random graph model and several small world networks is proportional to log N, the BA model exhibits D~loglogN (ultrasmall world).<ref>{{cite journal|last=Cohen|first=R. |title=Scale-free networks are ultrasmall|journal=Phys. Rev. Lett.|year=2003|volume=90|pages=058701|url=http://havlin.biu.ac.il/Publications.php?keyword=Scale-free+networks+are+ultrasmall&year=*&match=all|doi=10.1103/PhysRevLett.90.058701|pmid=12633404|first2=S.|last2=Havlin|issue=5|bibcode=2003PhRvL..90e8701C |arxiv=cond-mat/0205476}}</ref> + − Note that the average path length scales with N as the diameter.+
→Barabási–Albert (BA) 优先链接模型
|archivedate = 2012-04-17
|archivedate = 2012-04-17
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BA模型得到的度分布是无标度的，特别是它的形式是幂律：
: <math>P(k)\sim k^{-3} \, </math>
: <math>P(k)\sim k^{-3} \, </math>
中心节点表现出很高的介数中心性，这使得节点之间存在捷径。因此，BA模型的平均路径长度往往很短。该模型的聚类系数也趋于0。
包括Erdős Rényi随机图模型和一些小世界模型在内的很多网络模半径D正比于log N，但是BA模型表现出D~loglogN（超小世界）。<ref>{{cite journal|last=Cohen|first=R. |title=Scale-free networks are ultrasmall|journal=Phys. Rev. Lett.|year=2003|volume=90|pages=058701|url=http://havlin.biu.ac.il/Publications.php?keyword=Scale-free+networks+are+ultrasmall&year=*&match=all|doi=10.1103/PhysRevLett.90.058701|pmid=12633404|first2=S.|last2=Havlin|issue=5|bibcode=2003PhRvL..90e8701C |arxiv=cond-mat/0205476}}</ref>
注意，平均路径长度随N的变化和半径相同。
====Mediation-driven attachment (MDA) model====
====Mediation-driven attachment (MDA) model====