学术活动

主题:生物系统中的集体运动——鱼群、鸟群是如何形成的

演讲者:张何朋  上海交通大学自然科学研究院

时间:5月21日(周五)10:00

地点:东中院1-400号

内容简介:

Collections of motile organisms such as flocking birds, schooling fish, and swarming bacteria often exhibit collective motion with extended spatiotemporal coherence. While there are many qualitative observations, quantitative measurements of such collective motion have been limited. We measure simultaneously the positions, velocities, and orientations of up to a thousand bacteria in a colony. The motile bacteria form closely-packed dynamic clusters within which they move cooperatively. The number of bacteria in a cluster exhibits a power-law distribution truncated by an exponential tail. Mobile clusters cause anomalous fluctuations in bacterial density, i.e., fluctuations DN which vary with the mean N, not as DN µ N1/2 (as in a system in thermal equilibrium), but as DN µ N3/4.