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Physical Sciences and Mathematics Commons

Open Access. Powered by Scholars. Published by Universities.®

2010

Physics - All Scholarship

Statistical mechanics

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Full-Text Articles in Physical Sciences and Mathematics

Fluctuations And Pattern Formation In Self-Propelled Particles, Shradha Mishra, Aparna Baskaran, M. Cristina Marchetti Apr 2010

Fluctuations And Pattern Formation In Self-Propelled Particles, Shradha Mishra, Aparna Baskaran, M. Cristina Marchetti

Physics - All Scholarship

We consider a coarse-grained description of a system of self-propelled particles given by hydrodynamic equations for the density and polarization fields. We find that the ordered moving or flocking state of the system is unstable to spatial fluctuations beyond a threshold set by the self-propulsion velocity of the individual units. In this region, the system organizes itself into an inhomogeneous state of well-defined propagating stripes of flocking particles interspersed with low density disordered regions. Further, we find that even in the regime where the homogeneous flocking state is stable, the system exhibits large fluctuations in both density and orientational order. …


Nonequilibrium Statistical Mechanics Of Self-Propelled Hard Rods, Aparna Baskaran, M. Cristina Marchetti Feb 2010

Nonequilibrium Statistical Mechanics Of Self-Propelled Hard Rods, Aparna Baskaran, M. Cristina Marchetti

Physics - All Scholarship

Using tools of nonequilibirum mechanics, we study a model of self-propelled hard rods on a substrate in two dimensions to quantify the interplay of self-propulsion and excluded-volume effects. We derive of a Smoluchowski equation for the configurational probability density of self-propelled rods that contains several modifications as compared to the familiar Smoluchowski equation for thermal rods. As a side-product of out work, we also present a purely dynamical derivation of the Onsager form of the mean field excluded volume interaction among thermal hard rods.