title: Hydrodynamic fluctuations and instabilities in ordered suspensions of self-propelled particles.
abstract: We construct the hydrodynamic equations for suspensions of self-propelled particles (SPPs) with spontaneous orientational order, and make a number of striking, testable predictions: (i) Nematic SPP suspensions are always absolutely unstable at long wavelengths. (ii) SPP suspensions support novel propagating modes at long wavelengths, coupling orientation, flow, and concentration. (iii) In a wave number regime accessible only in low Reynolds number systems such as bacteria, polar-ordered suspensions are invariably convectively unstable. (iv) The variance in the number N of particles, divided by the mean <N>, diverges as <N >(2/3 ) in polar-ordered SPP suspensions.
authors.affiliation: Centre for Condensed-Matter Theory, Department of Physics, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: R
authors.initials: R
authors.lastname: Aditi Simha
authors.forename: Sriram
authors.initials: S
authors.lastname: Ramaswamy
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D002465:Cell Movement; D007962:Leukocytes / Q000166:cytology; D008544:Melanocytes / Q000166:cytology; D008954:Models, Biological; D009068:Movement