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Authors: Christoph A. Weber, Erwin Frey
Even simple active systems show a plethora of intriguing phenomena and often we find complexity were we would have expected simplicity. One striking example is the occurrence of an absorbing state with frozen fluctuations that at first sight seems to be impossible for active matter driven by the incessant input of energy. In high density motility assay experiments frozen ring like structures, in open and closed conformations, arise if active transport is coupled to growth processes that is mediated by molecular linker molecules. Here, we present a minimal theoretical model that accounts for the emergence of closed and open rings. The model includes only two competing processes - continuous lateral growth and irreversible merging of actively transported filament-bundles - that already suffice to retrieve the experimentally observed coexistence of open and closed rings. Omission of one of these processes leads to the formation of either closed or open rings. We find cumulative radii distributions for open and closed rings decay approximate exponentially in accordance with experimental observations. Moreover, the simulations allow for a backtracking of the steady state properties to the system's inherent noise given the molecular motor concentration on the surface. We reveal how this noise determines the stochasticity of each string's trajectory: Larger motor concentrations lead to an increase in the fraction of open to closed rings. |
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