1. Department of Mathematical and Life Sciences, Hiroshima University, Higashihiroshima, Hiroshima 739-8526, Japan
2. Advanced ICT Research Institute Kobe, National Institute of Information and Communications Technology, Kobe 651-2492, Japan
3. Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan
4. Research Center for Mathematics on Chromatin Live Dynamics, Hiroshima University, Higashihiroshima, Hiroshima 739-8526, Japan