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Title: Birth, Death, and Flight: the hydrodynamics of Malthusian flocks

Invited

Abstract

I'll present the hydrodynamic theory of ``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 =2. Their spatiotemporal scaling structure can be determined exactly in d=2; 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. I'll also present recent results for the three dimensional version of this problem, which required the first full blown dynamical renormalization treatment of a flocking system in its ordered phase.

Presenters

  • John J Toner

    Department of Physics, University of Oregon, Univ of Oregon

Authors

  • John J Toner

    Department of Physics, University of Oregon, Univ of Oregon