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記
日時：２０１８年１０月１９日（金）１３時３０分〜
場所：東京大学 生産技術研究所 千葉実験所 研究実験棟Ｉn210号室
道程：http://hatano-lab.iis.u-tokyo.ac.jp/access.html
講師：島田尚さん（東大工）
演題：A complexity-robustness relation in evolving open systems
要旨：An important and universal feature of real large complex systems, such as social, economic, ecological, and biological systems, is that they are open. The complex structure they have today has been acquired through the successive introductions of new elements, and they are at least persisting against the further introduction process. Those systems indeed sometimes grow, but also sometimes collapse. Therefore why and when, in general, we can have such open and complex systems is a fundamental question.
In this talk, I will introduce our recent approach to this classical problem based on a very simple graph model. I will show that this model gives either continuous growth to a infinite size or stagnation in system size, depending on the model’s unique parameter m: the average number of weighted links per node. The system can grow only if the connection is moderately sparse, i.e. 4 < m < 19. We can further find that this transition originates from an essential balance of two effects: although having more interactions makes each node robust, it also increases the impact of the loss of a node [1, 2]. This novel relation might be a origin of the moderately sparse (average degree 10) network structure ubiquitously found in real world.
The interaction in many real systems, however, often has intrinsically bidirectional nature like mutual symbiosis, predation, and competition in ecology. I will introduce our study on the model with bidirectional interactions [3].
参考文献
[1] T. Shimada, Scientific Reports Vol. 4, 4082 (2014).
[2] T. Shimada, in Springer monograph Mathematical Approaches to Biological Systems: networks, Oscillations and Collective Motions (Springer, 2015) p. 95-117.
[3] F. Ogushi, J. Kert?sz, K. Kaski, & T. Shimada, Scientific Reports Vol. 7, 6978 (2017).
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李 宰河
〒277-8574 千葉県柏市柏の葉5-1-5
東京大学生産技術研究所
e-mail: lee@iis.u-tokyo.ac.jp
Tel: 04-7136-6977
Fax: 04-7136-6978
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