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Collective Motion of Active Brownian Particles at High Densities
##manager.scheduler.building##: Edificio San Alberto Magno
##manager.scheduler.room##: Auditorio Santa Cecilia
Date: 2019-07-11 03:30 PM – 03:45 PM
Last modified: 2019-07-02
Abstract
Active Brownian Particles (ABP) arguably comprise one of the simplest models to
study the effect of "active" self-propulsion forces in classical statistical
physics and hence the features of intrinsically non-equilibrium condensed
matter. They combine passive Brownian motion with directed motion along a
randomly reorienting body axis. We specifically study active Brownian disks (in
two spatial dimensions) to investigate the influence of spherically symmetric
steric repulsion with the active driving force. A lot of emphasis has been
placed so far on the collective dynamics of ABP at intermediate densities,
where a clustering phenomenon termed motility-induced phase separation (MIPS)
is seen. Less is known at high densities. Here, simulations of ABP systems show
a transition from the homogeneous fluid to an "active glass" state.
We discuss the high-density dynamics of ABP with the help of Brownian dynamics
simulations and of a mode-coupling theory for the active glass transition [1].
The theory predicts kinetic arrest that depends non-trivially on the interplay
between the persistence length of the active motion and the caging length set
by excluded-volume interactions. Simulations reveal that the kinetic-arrest
transition predicted by the theory separates qualitatively different regimes
for the long-time dynamics with regard to the dependence of the paramters
controlling the particles' activity. This can be linked to a discussion in how
far kinetic parameters of the motion (such as short-time diffusivities) enter
the long-time fate (fluid or glassy) of high-density states [2].
Combined with the integration-through transients (ITT) mechanism, a formalism
to systematically derive Green-Kubo like expressions for transport coefficients
also far from equilibrium, and standard effective free-energy arguments, the
mode-couping theory makes predictions for a state diagram for ABP comprising
both kinetically arrested and phase-separated states.
[1] A. Liluashvili, J. Onody, and Th. Voigtmann, Phys. Rev. E 96, 062608 (2017).
[2] S. Mandal, T. Franosch, and Th. Voigtmann, Soft Matter 14, 9153 (2018).
study the effect of "active" self-propulsion forces in classical statistical
physics and hence the features of intrinsically non-equilibrium condensed
matter. They combine passive Brownian motion with directed motion along a
randomly reorienting body axis. We specifically study active Brownian disks (in
two spatial dimensions) to investigate the influence of spherically symmetric
steric repulsion with the active driving force. A lot of emphasis has been
placed so far on the collective dynamics of ABP at intermediate densities,
where a clustering phenomenon termed motility-induced phase separation (MIPS)
is seen. Less is known at high densities. Here, simulations of ABP systems show
a transition from the homogeneous fluid to an "active glass" state.
We discuss the high-density dynamics of ABP with the help of Brownian dynamics
simulations and of a mode-coupling theory for the active glass transition [1].
The theory predicts kinetic arrest that depends non-trivially on the interplay
between the persistence length of the active motion and the caging length set
by excluded-volume interactions. Simulations reveal that the kinetic-arrest
transition predicted by the theory separates qualitatively different regimes
for the long-time dynamics with regard to the dependence of the paramters
controlling the particles' activity. This can be linked to a discussion in how
far kinetic parameters of the motion (such as short-time diffusivities) enter
the long-time fate (fluid or glassy) of high-density states [2].
Combined with the integration-through transients (ITT) mechanism, a formalism
to systematically derive Green-Kubo like expressions for transport coefficients
also far from equilibrium, and standard effective free-energy arguments, the
mode-couping theory makes predictions for a state diagram for ABP comprising
both kinetically arrested and phase-separated states.
[1] A. Liluashvili, J. Onody, and Th. Voigtmann, Phys. Rev. E 96, 062608 (2017).
[2] S. Mandal, T. Franosch, and Th. Voigtmann, Soft Matter 14, 9153 (2018).