Wired covers a new article in Nature, investigating massive failures in linked networks.
The interesting thing is that feedback between the connected networks destabilizes the whole:
“When networks are interdependent, you might think they’re more stable. It might seem like we’re building in redundancy. But it can do the opposite,” said Eugene Stanley, a Boston University physicist and co-author of the study, published April 14 in Nature.
…
The interconnections fueled a cascading effect, with the failures coursing back and forth. A damaged node in the first network would pull down nodes in the second, which crashed nodes in the first, which brought down more in the second, and so on. And when they looked at data from a 2003 Italian power blackout, in which the electrical grid was linked to the computer network that controlled it, the patterns matched their models’ math.
Interestingly, the interconnection alters the relationship between network structure (degree distribution) and robustness:
Surprisingly, a broader degree distribution increases the vulnerability of interdependent networks to random failure, which is opposite to how a single network behaves.
Chalk one up for counter-intuitive behavior of complex systems.
What looks like last year’s version of the paper is on arXiv.