Incollection,
Out-of-equilibrium dynamics of self-propelled particles
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)
Abstract
Dynamics in the cell involve not only passive diffusive
processes ($E k_B T$) but also active transport
($Ek_B T$) which consumes chemical energy.
At the scale of a biological cell, in order to form and
function, structures such as the cytoskeleton require
activation of chemical motors which use and dissipate energy.
Due to the presence of these active processes, these systems
exhibit a rich variety of viscoelastic properties, i.e., they
are able to rearrange their structure and change
from plastic/fluid to elastic/solid phases and vice versa.
In order to understand the main properties of such complex
systems we consider a simple model: a system of spherical
particles interacting via a two-body Lennard Jones-like
potential, where the range of the attraction is much shorter
than the hard core radius. Particles are attached to
motors which activate and displace them, following a
stochastic process. The actual implementation of the stochastic
rules can be chosen in order to mimic the realistic chemical
processes. The non-conservative motor forces drive the system
in out-of-equilibrium conditions. The control of their intensity
and direction allows one to drive the system into steady states
(weak perturbation) or into states far from equilibrium
(strong perturbation).
We study structure and out-of-equilibrium dynamics of the above
system of self-propelled particles via Brownian molecular dynamics
computer simulations. We investigate the stability of the different
phases and the range of validity of the Fluctuation Dissipation
theorem for several realizations of the motor processes.
We finally speculate on the possibility to define an effective
temperature for this class of systems.
