1,874 research outputs found
Criticality and the Onset of Ordering in the Standard Vicsek Model
Experimental observations of animal collective behavior have shown stunning
evidence for the emergence of large-scale cooperative phenomena resembling
phase transitions in physical systems. Indeed, quantitative studies have found
scale-free correlations and critical behavior consistent with the occurrence of
continuous, second-order phase transitions. The Standard Vicsek Model (SVM), a
minimal model of self-propelled particles in which their tendency to align with
each other competes with perturbations controlled by a noise term, appears to
capture the essential ingredients of critical flocking phenomena. In this
paper, we review recent finite-size scaling and dynamical studies of the SVM,
which present a full characterization of the continuous phase transition
through dynamical and critical exponents. We also present a complex network
analysis of SVM flocks and discuss the onset of ordering in connection with
XY-like spin models.Comment: 15 pages, 4 figures. To appear in Interface Focu
Active Brownian Particles. From Individual to Collective Stochastic Dynamics
We review theoretical models of individual motility as well as collective
dynamics and pattern formation of active particles. We focus on simple models
of active dynamics with a particular emphasis on nonlinear and stochastic
dynamics of such self-propelled entities in the framework of statistical
mechanics. Examples of such active units in complex physico-chemical and
biological systems are chemically powered nano-rods, localized patterns in
reaction-diffusion system, motile cells or macroscopic animals. Based on the
description of individual motion of point-like active particles by stochastic
differential equations, we discuss different velocity-dependent friction
functions, the impact of various types of fluctuations and calculate
characteristic observables such as stationary velocity distributions or
diffusion coefficients. Finally, we consider not only the free and confined
individual active dynamics but also different types of interaction between
active particles. The resulting collective dynamical behavior of large
assemblies and aggregates of active units is discussed and an overview over
some recent results on spatiotemporal pattern formation in such systems is
given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte
Identifying manifolds underlying group motion in Vicsek agents
Collective motion of animal groups often undergoes changes due to
perturbations. In a topological sense, we describe these changes as switching
between low-dimensional embedding manifolds underlying a group of evolving
agents. To characterize such manifolds, first we introduce a simple mapping of
agents between time-steps. Then, we construct a novel metric which is
susceptible to variations in the collective motion, thus revealing distinct
underlying manifolds. The method is validated through three sample scenarios
simulated using a Vicsek model, namely switching of speed, coordination, and
structure of a group. Combined with a dimensionality reduction technique that
is used to infer the dimensionality of the embedding manifold, this approach
provides an effective model-free framework for the analysis of collective
behavior across animal species.Comment: 12 pages, 6 figures, journal articl
The role of neighbours selection on cohesion and order of swarms
We introduce a multi-agent model for exploring how selection of neighbours
determines some aspects of order and cohesion in swarms. The model algorithm
states that every agents' motion seeks for an optimal distance from the nearest
topological neighbour encompassed in a limited attention field. Despite the
great simplicity of the implementation, varying the amplitude of the attention
landscape, swarms pass from cohesive and regular structures towards fragmented
and irregular configurations. Interestingly, this movement rule is an ideal
candidate for implementing the selfish herd hypothesis which explains
aggregation of alarmed group of social animals.Comment: 15 pages, 9 figures, Plos One, May 201
- …