1. Complexity & Networks Group and Department of MathematicsImperial College LondonSouth Kensington CampusSW7 2AZ United Kingdom
2. Department of Computational Intelligence and Systems ScienceTokyo Institute of Technology4259‐G3‐52 Nagatsuta‐choMidori‐ku Yokohama226‐8502 Japan
3. The Canon Institute for Global Studies11F, Shin‐MarunouchiChiyoda‐ku Tokyo100‐6511 Japan
4. Sony Computer Science Laboratories3‐14‐13 HigashigotandaShinagawa‐ku Tokyo141‐0022 Japan
5. Meiji Institute of Advanced Study of Mathematical Sciences, Meiji University1‐1‐1 HigashimitaTama‐ku Kawasaki214‐8571 Japan