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Article Dans Une Revue EPL - Europhysics Letters Année : 2013

When are active Brownian particles and run-and-tumble particles equivalent? Consequences for motility-induced phase separation

Résumé

Active Brownian particles (ABPs, such as self-phoretic colloids) swim at fixed speed $v$ along a body-axis ${\bf u}$ that rotates by slow angular diffusion. Run-and-tumble particles (RTPs, such as motile bacteria) swim with constant $\u$ until a random tumble event suddenly decorrelates the orientation. We show that when the motility parameters depend on density $\rho$ but not on ${\bf u}$, the coarse-grained fluctuating hydrodynamics of interacting ABPs and RTPs can be mapped onto each other and are thus strictly equivalent. In both cases, a steeply enough decreasing $v(\rho)$ causes phase separation in dimensions $d=2,3$, even when no attractive forces act between the particles. This points to a generic role for motility-induced phase separation in active matter. However, we show that the ABP/RTP equivalence does not automatically extend to the more general case of $\u$-dependent motilities.

Dates et versions

hal-00903637 , version 1 (12-11-2013)

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M. E. Cates, J. Tailleur. When are active Brownian particles and run-and-tumble particles equivalent? Consequences for motility-induced phase separation. EPL - Europhysics Letters, 2013, 101, pp.20010. ⟨10.1209/0295-5075/101/20010⟩. ⟨hal-00903637⟩
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