Precisely cyclic sand: Self-organization of periodically sheared frictional grains

John R. Royer, Paul M. Chaikin

    Research output: Contribution to journalArticlepeer-review


    The disordered static structure and chaotic dynamics of frictional granular matter has occupied scientists for centuries, yet there are few organizational principles or guiding rules for this highly hysteretic, dissipative material. We show that cyclic shear of a granular material leads to dynamic self-organization into several phases with different spatial and temporal order. Using numerical simulations, we present a phase diagram in strain-friction space that shows chaotic dispersion, crystal formation, vortex patterns, and most unusually a disordered phase in which each particle precisely retraces its unique path. However, the system is not reversible. Rather, the trajectory of each particle, and the entire frictional, many-degrees-of-freedom system, organizes itself into a limit cycle absorbing state. Of particular note is that fact that the cyclic states are spatially disordered, whereas the ordered states are chaotic.

    Original languageEnglish (US)
    Pages (from-to)49-53
    Number of pages5
    JournalProceedings of the National Academy of Sciences of the United States of America
    Issue number1
    StatePublished - Jan 6 2015


    • Friction
    • Granular
    • Limit cycles
    • Self-organization

    ASJC Scopus subject areas

    • General


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