Nonlinear Systems Laboratory

A. Fujioka

H. Kubotani

Hiroto Kubotani

Office: 6-410 Ext.: 3375


03/1992, Ph.D., Kyoto University

03/1988, M.S., Kyoto University

T. Sasaki

R. Fujie

Ryo Fujie
(Assistant Professor)

Office: 5-221 Ext.: 3114


03/2010, Ph.D., Kyushu University

03/2007, M.S., Kyushu University

Research Field

Nonlinear Systems theory, Complex Systems theory, Statistical Science, Sociophysics

Research Subjects

  • 1. Dynamical formation of quantum entanglement and its applications
  • 2. Sociophysics


A best-selling product will often sell well because consumers know that it is selling well. This shows that consumers are affected by each other. If behaviors of the consumers go along with, a social tendency arises as a result of the summation of many individual personal activities. This phenomenon is similar to a macroscopic magnet, which is composed of many aligned magnetic spins. This type of phenomenon can be observed in human society and in nature.
For the study of a complex system that consists of many interacting elements, it is modeled in a nonlinear system. In our laboratory, we study a complex system that consists of many interacting elements. To reveal properties of the system, we use nonlinear systems theory and statistical science. We usually build a nonlinear system model of the complex system and estimate its validity through computer simulations.

  • 1) H. Kubotani, S. Adachi, M. Toda, "Measuring dynamical randomness of quantum chaos by statistics of Schmidt eigenvalues", Physical Review E 87 (2013), 062921.
  • 2) H. Kubotani, S. Adachi and M. Toda, "Exact Formula of the Distribution of Schmidt Eigenvalues for Dynamical Formation of Entanglement in Quantum Chaos", Physical. Review. Letters 100 (2006), 240501.
  • 3) R. Fujie, K. Aihara and N. Masuda, "A model of competition among more than two languages", Journal of Statistical. Physics 151 (2013), 289-303.
Affiliated Academic Organizations

H. Kubotani:
The Information Processing Society of Japan, the Physical Society of Japan, the Astronomical Society of Japan, the Japanese Society for Planetary Sciences

R. Fujie:
the Physical Society of Japan

Current members
◯ Professors: 1 ◯ Assistant Professors: 1
◯ Postgraduates: 1 ◯ Undergraduates: 27