Sommaire:

What determines the mechanical properties of dense collections of active
particles? The answer to this
question is highly relevant to a wide range of physical and biological
phenomena from tissue formation
to the dynamics of vibrated granular layers. We present a numerical study of
the phases and dynamics
of a dense collection of self-propelled particles with soft repulsive
interactions with and without polar alignment.

The phase diagram of the confined aligning system consists of a polar liquid
phase at low
packing fraction and high self-propulsion speed, and an active jammed phase
at high density and low
self-propulsion speed. The liquid phase exhibits local alignment and giant
number fluctuations typical
of the Vicsek class of models. The dynamics of the jammed phase is dominated
by oscillations along
the low frequency modes of the underlying packing. We show analytically that
at long times the energy
is carried entirely by the lowest available excitations of the system. We
measure and compare the local stresses in our active system, with added
attraction, to both granular materials and the tissue experiments.

Pour plus d'informations, merci de contacter Berthier L.