TY  - JOUR
A1  - Großmann, Robert
A1  - Aranson, Igor S.
A1  - Peruani, Fernando
T1  - A particle-field approach bridges phase separation and collective motion in active matter
JF  - Nature Communications
N2  - Whereas self-propelled hard discs undergo motility-induced phase separation, self-propelled rods exhibit a variety of nonequilibrium phenomena, including clustering, collective motion, and spatio-temporal chaos. In this work, we present a theoretical framework representing active particles by continuum fields. This concept combines the simplicity of alignment-based models, enabling analytical studies, and realistic models that incorporate the shape of self-propelled objects explicitly. By varying particle shape from circular to ellipsoidal, we show how nonequilibrium stresses acting among self-propelled rods destabilize motility-induced phase separation and facilitate orientational ordering, thereby connecting the realms of scalar and vectorial active matter. Though the interaction potential is strictly apolar, both, polar and nematic order may emerge and even coexist. Accordingly, the symmetry of ordered states is a dynamical property in active matter. The presented framework may represent various systems including bacterial colonies, cytoskeletal extracts, or shaken granular media. Interacting self-propelled particles exhibit phase separation or collective motion depending on particle shape. A unified theory connecting these paradigms represents a major challenge in active matter, which the authors address here by modeling active particles as continuum fields.
Y1  - 2020
U6  - https://doi.org/10.1038/s41467-020-18978-5
SN  - 2041-1723
VL  - 11
IS  - 1
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Aranson, Igor S.
A1  - Pikovskij, Arkadij
T1  - Confinement and collective escape of active particles
JF  - Physical review letters
N2  - Active matter broadly covers the dynamics of self-propelled particles. 
While the onset of collective behavior in homogenous active systems is relatively well understood, the effect of inhomogeneities such as obstacles and traps lacks overall clarity. 
Here, we study how interacting, self-propelled particles become trapped and released from a trap. 
We have found that captured particles aggregate into an orbiting condensate with a crystalline structure. As more particles are added, the trapped condensates escape as a whole. 
Our results shed light on the effects of confinement and quenched disorder in active matter.
Y1  - 2022
U6  - https://doi.org/10.1103/PhysRevLett.128.108001
SN  - 0031-9007
SN  - 1079-7114
SN  - 1092-0145
VL  - 128
IS  - 10
PB  - American Physical Society
CY  - College Park, Md.
ER  -