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 [email protected] 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 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 selfpropelled 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).