Abstract Networks
WWW (2000)
Scientific Collaboration Girvan & Newman (2002)
Sexual Contact Potterat et al. (2002)
Community Structure Moody (2001)
SocialFriendships Business Relationships Sexual relationships Small World Networks InformationWWW citation Thesaurus TechnologicalInternet Power Grid Train, Plane, Road, River Routes BiologicalNeural Network Metabolic Protein Interactions Circulatory System
Some Questions to ask About Networks Technological Networks (eg Internet) Information Networks (eg WWW) Social Networks
Random N = 20 Av-k = 5
Bell-Shaped Distribution
Barabasi’s Results
Power-Law Distribution
P(k) prob that node is connected to k other nodes Web Log-log
Scale Free Dia = 4
How are Scale-Free Networks Built?
Applications of Abstract Scale-Free Thinking
Diameter of the Web Albert, Jeong & Barabasi (1999) Nature. Definition 1 (Barabasi) “average of the shortest paths between all nodes. Definition 2 The longest of all shortest nodes.
Scale Free Dia = 4
Scale Free Dia = 4
Random Attack Nodes 1,12,18
Targeted Attack Nodes 4,5,6
Random N = 20 Av-k = 5
Random Attack Nodes 1,2,18
Targeted Attack Nodes 1,2,18
Network Resilience
Small Worlds – Social Networks N people in the world with z acquaintances. How many links l needed to get from and person to any other person?