title: Macroscopic traveling packet and soliton states of quasi-one-dimensional flocks.
abstract: Using a continuum model for inhomogeneous flocks, we show that a finite but arbitrarily large moving "packet" of active particles (e.g., moving creatures) can form in a background of a lower density disordered phase of these particles, like a liquid drop surrounded by vapor. The "vapor density" of the disordered background can be made arbitrarily low. We find three basic types of quasi-one-dimensional states: "longitudinal", "transverse", and "oblique" states, with their internal velocity fields, respectively, parallel, perpendicular, and oblique to the interface. The transitions between these states are also studied.
authors.affiliation: Institute for Theoretical Science and Department of Physics, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Guttenberg
authors.affiliation: Institute for Theoretical Science and Department of Physics, University of Oregon, Eugene, Oregon 97403, USA.
authors.forename: John
authors.initials: J
authors.lastname: Toner
authors.affiliation: IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA.
authors.forename: Yuhai
authors.initials: Y
authors.lastname: Tu
mesh_terms: D003198:Computer Simulation; D057446:Hydrodynamics; D008962:Models, Theoretical; D009038:Motion; D011312:Pressure