東京大学の西口さんのセミナーが開催!

東京大学の西口さんのセミナーが開催!

タイトル:Experimental approaches to understanding statistical mechanics of collective motion in active matter: filamentous bacteria & Janus particles

要旨:Although there are many numerical and theoretical studies on collective motion in active matter such as Vicsek-like models, there have been no convincing experiments that have clearly observed predicted properties such as giant number fluctuations in ordered states. In this seminar, after reviewing basic models of collective motion with different symmetries [1-3], I will introduce two of our experimental systems and their results, which are consistent with former numerical and theoretical works.

One is a system of filamentous bacteria, which are 20 times as long as usual bacteria. Due to strong alignment interactions arising from their elongated shapes, these bacteria exhibit a nematic state. It shows true long-range order and giant number fluctuations. All the obtained experimental results are consistent with the Vicsek-like self-propelled rods model [3], in which each particle has polarity and their interactions are nematic as in our experiments.
The other system is that of Janus particles self-propelling under an AC electric field. Each Janus particle has polarity and their interactions are ferromagnetic, which is the same as in the original Vicsek model [1]. Our Janus particles exhibit disordered states, turbulent states and ordered states, and we will show our experimental observations on statistical properties of these states [4] such as velocity correlations and number fluctuations.

[1] T. Vicsek, et al. Phys. Rev. Lett. 75, 6 (1995), H. Chaté, et al., Eur. Phys. J. B 64, 451 (2008); [2] S. Ngo, et al., Phys. Rev. Lett. 113, 038302 (2014); [3] F. Ginelli, et al., Phys. Rev. Lett. 104, 184502 (2010); [4] D. Nishiguchi and M. Sano, Phys. Rev. E 92, 052309 (2015)


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セミナー後にはZianeさん、隣の複雑物性基礎(木村グループ)のスタッフでお昼をたべにいきました!

更新日:2015年12月11日