第 22 回

1. 第22回 北大ＭＭＣセミナー Date：2014年3月6日（木） 14:30～16:00 ※通常と曜日・時間が異なります Speaker：太田　隆夫（京都大学名誉教授） Place：電子科学研究所　中央キャンパス総合研究棟2号館　 5F講義室 北（北12条西７丁目） Title：Collective dynamics of self-propelled soft particles Abstract：別紙をご参照ください 連絡先： 北海道大学 電子科学研究所 　　　　　　　　　 動的数理モデリング研究室 　　 　 長山　雅晴　　内線　3357 nagayama@es.hokudai.ac.jp 主催：　電子科学研究所　動的数理モデリング研究室 共催：　北海道大学数学連携研究センター　　　　　　　　

2. Abstract： Dynamics of interacting self-propelled objects has attracted much attention recently from the view point of nonlinear science and nonequilibrium statistical physics [1]. One of the characteristic features of collective dynamics is that homogeneous ordered state where all the particles are traveling coherently to a certain direction at a constant velocity becomes unstable near the order-disorder transition point and traveling bands appear in the matrix of the disordered state [2]. In my talk, I will describe our recent study of interacting self-propelled soft particles whose migration velocity increases with increasing local density [3]. By the word “soft”, I mean that particles are deformable. This is motivated by the fact that there is a coupling between the velocity of the center of mass and shape deformation in the motion of a living cell. Numerical simulations in two dimensions reveal that traveling bands similar to those found previously in the Vicsek-type model are easily formed by this local density dependence of the migration velocity. We show that a pair of stripe bands which are traveling to the opposite direction is not destructed by a head-on collision but survives again after collision. This soliton-like behavior has also been observed quite recently in density waves in non-chemotactic Dictyostelium discoideum mutants [4]. Similarity to and difference from the experimental results are discussed [5]. [1] T. Vicsek and A. Zafeiris, Phys. Rep. 517, 71 (2012). [2] H. Chate, F. Ginelli, G. Gregoire, and F. Raynaud, Phys. Rev. E 77, 046113 (2008). [3] S. Yamanaka and T. Ohta, Phys. Rev. E89 021918 (2014). [4] H. Kuwayama and S. Ishida, Sci. Rep. 3, 2272; DOI:10.1038/srep02272 (2013). [5] T. Ohta and S. Yamanaka, Prog. Theor. Exp. Phys. 2014 011J01 (2014).