2011/08/31 by John Toner · 1 citation
Physics and Astronomy · #cond-mat.other #cond-mat.soft
paper · pdf · doi:10.1103/physrevlett.108.088102
4 pages; revised in response to referee comments
arxiv created 2011/12/11 · arxiv updated 2013/05/29
I study "Malthusian Flocks": moving aggregates of self-propelled entities (e.g., organisms, cytoskeletal actin, microtubules in mitotic spindles) that reproduce and die. Long-ranged order (i.e., the existence of a non-zero average velocity < v ( r, t) >≠ 0) is possible in these systems, even in spatial dimension d=2. Their spatio-temporal scaling structure can be determined exactly in all spatial dimensions; furthermore, they lack both the longitudinal sound waves and the giant number fluctuations found in immortal flocks. Number fluctuations are very \it persistent, and propagate along the direction of flock motion, but at a different speed.