Blog: Society's Vital Networks Prone to 'Explosive' Changes

Society's Vital Networks Prone to 'Explosive' Changes
New Scientist (03/13/09) Barras, Colin

Researchers led by University of California, Santa Cruz professor Dimitris Achlioptas have discovered that controlling the develop of random networks could lead to a better understanding of how to slow or stop the spread of diseases or make delivery networks more efficient. Networks that grow randomly, such as the connections between computers that create the Internet, often quickly gain a central backbone of connections that makes it easy to travel between any two points. The researchers used simulations to find a way of growing a network randomly while delaying the emergence of the backbone. However, they found that when the network becomes fully connected it tends to occur in an explosive manner. Random networks usually grow by selecting two random nodes that become connected. Instead, the researchers picked two pairs of random nodes, but only connected the pair with the fewest pre-existing connections to other nodes. The result is a network that grows steadily but does not become fully connected for a longer time. Eventually, the addition of a single connection triggers an instantaneous phase change and the network becomes fully connected. A variation of this technique makes it possible to execute the opposite process and accelerate the development of a network's backbone. "We know that for some networks, like the Internet, connectivity is a fundamental desired property," says research team member Raissa D'Souza from the University of California, Davis. "For others, like a virus spreading through a network of humans or computers, connectivity is a liability."

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