scholarly journals Collective Movement and Collective Information Acquisition With Signaling

2021 ◽  
Vol 9 ◽  
Author(s):  
Mohammad Salahshour ◽  
Shahin Rouhani
Keyword(s):  
Information Acquisition ◽  
Collective Motion ◽  
Large Fraction ◽  
Finite Size ◽  
Density Fluctuations ◽  
Movement Direction ◽  
Vicsek Model ◽  
High Fraction ◽  
Two Phases ◽  
Collective Information

We consider a population of mobile agents able to make noisy observations of the environment and communicate their observation by production and comprehension of signals. Individuals try to align their movement direction with their neighbors. Besides, they try to collectively find and travel towards an environmental direction. We show that, when the fraction of informed individuals is small, by increasing the noise in communication, similarly to the Vicsek model, the model shows a discontinuous order-disorder transition with strong finite-size effects. In contrast, for a large fraction of informed individuals, it is possible to go from the ordered phase to the disordered phase without passing any phase transition. The ordered phase is composed of two phases separated by a discontinuous transition. Informed collective motion, in which the population collectively infers the correct environmental direction, occurs for a high fraction of informed individuals. When the fraction of informed individuals is low, the misinformed collective motion, where the population fails to find the environmental direction, becomes stable as well. Besides, we show that an amount of noise in the production of signals is more detrimental for the inference capability of the population and increases temporal fluctuations, the density fluctuations, and the probability of group fragmentation, compared to the same amount of noise in the comprehension.

scholarly journals Symmetry-breaking phase transitions in highly concentrated semen

2016 ◽  
Vol 13 (123) ◽  
pp. 20160575 ◽  
Author(s):  
Adama Creppy ◽  
Franck Plouraboué ◽  
Olivier Praud ◽  
Xavier Druart ◽  
Sébastien Cazin ◽  
...  
Keyword(s):  
Collective Motion ◽  
Sperm Concentration ◽  
Vortex State ◽  
Local Alignment ◽  
Macroscopic Theory ◽  
Vicsek Model ◽  
Highly Active ◽  
Self Organized ◽  
Self Motion ◽  
Fresh Semen

New experimental evidence of self-motion of a confined active suspension is presented. Depositing fresh semen sample in an annular shaped microfluidic chip leads to a spontaneous vortex state of the fluid at sufficiently large sperm concentration. The rotation occurs unpredictably clockwise or counterclockwise and is robust and stable. Furthermore, for highly active and concentrated semen, richer dynamics can occur such as self-sustained or damped rotation oscillations. Experimental results obtained with systematic dilution provide a clear evidence of a phase transition towards collective motion associated with local alignment of spermatozoa akin to the Vicsek model. A macroscopic theory based on previously derived self-organized hydrodynamics models is adapted to this context and provides predictions consistent with the observed stationary motion.

Discontinuous and continuous transitions of collective behaviors in living systems

2021 ◽  
Author(s):  
Xu Li ◽  
Tingting Xue ◽  
Yu Sun ◽  
Jingfang Fan ◽  
Hui Li ◽  
...  
Keyword(s):  
Cognitive Abilities ◽  
Collective Motion ◽  
Finite Size ◽  
Continuous Phase ◽  
Living System ◽  
Living Systems ◽  
Finite Size Scaling ◽  
Continuous Transition ◽  
Collective Behaviors ◽  
Large Groups

Abstract Living systems are full of astonishing diversity and complexity of life. Despite differences in the length scales and cognitive abilities of these systems, collective motion of large groups of individuals can emerge. It is of great importance to seek for the fundamental principles of collective motion, such as phase transitions and their natures. Via an eigen microstate approach, we have found a discontinuous transition of density and a continuous transition of velocity in the Vicsek models of collective motion, which are identified by the finite-size scaling form of order-parameter. At strong noise, living systems behave like gas. With the decrease of noise, the interactions between the particles of a living system become stronger and make them come closer. The living system experiences then a discontinuous gas-liquid like transition of density. The even stronger interactions at smaller noise make the velocity directions of particles become ordered and there is a continuous phase transition of collective motion in addition.

The rapid distortion of two-way coupled particle-laden turbulence

2019 ◽  
Vol 877 ◽  
pp. 82-104 ◽  
Author(s):  
M. Houssem Kasbaoui ◽  
Donald L. Koch ◽  
Olivier Desjardins
Keyword(s):  
Single Phase ◽  
Density Fluctuations ◽  
Gravitational Potential Energy ◽  
Inertial Particles ◽  
Mass Loading ◽  
Number Density ◽  
Turbulence Statistics ◽  
Preferential Sampling ◽  
Gravitational Loading ◽  
Two Phases

In this study, we address the modification of sheared turbulence by dispersed inertial particles. The preferential sampling of the straining regions of the flow by inertial particles in turbulence leads to an inhomogeneous distribution of particles. The strong gravitational loading exerted by the highly concentrated regions results in anisotropic alteration of turbulence at small scales in the direction of gravity. These effects are investigated in a rapid distortion theory (RDT) extended for two-way coupled particle-laden flows. To make the analysis tractable, we assume that particles have small but non-zero inertia. In the classical results for single-phase flows, the RDT assumption of fast shearing compared to the turbulence time scales leads to the distortion and shear-induced production of turbulence. In particle-laden turbulence, the coupling between the two phases under rapid shearing induces number density fluctuations that convert gravitational potential energy to turbulent kinetic energy and modulate the turbulence spectrum in a manner that increases with mass loading. Turbulence statistics obtained from RDT are compared with Euler–Lagrange simulations of homogeneously sheared particle-laden turbulence.

scholarly journals The Turbulent Star Formation Model - Outline and Tests

2004 ◽  
Vol 221 ◽  
pp. 51-58 ◽  
Author(s):  
Enrique Vázquez-Semadeni
Keyword(s):  
Star Formation ◽  
Column Density ◽  
Large Fraction ◽  
Density Fluctuations ◽  
Current Status ◽  
Density Profiles ◽  
Magnetic Turbulence ◽  
Cloud Cores ◽  
Formation Efficiency ◽  
Internal Velocity

We summarize the current status of the turbulent model of star formation in turbulent molecular clouds. In this model, clouds, clumps and cores form a hierarchy of nested density fluctuations caused by the turbulence, and either collapse or re-expand. Cores that collapse can be either internally sub- or super-sonic. The former cannot further fragment, and can possibly be associated with the formation of a single or a few stars. The latter, instead, can undergo turbulent fragmentation during their collapse, and probably give rise to a cluster of bound objects. The star formation efficiency is low because only a small fraction of the density fluctuations proceed to collapse. Those that do not may constitute a class of “failed” cores that can be associated with the observed starless cores. “Synthetic” observations of cores in numerical simulations of non-magnetic turbulence show that a large fraction of them have subsonic internal velocity dispersions, can be fitted by Bonnor-Ebert column density profiles, and exhibit “coherence” (an apparent independence of linewidth with column density near the projected core centers), in agreement with observed properties of molecular cloud cores.

Modeling collective motion: variations on the Vicsek model

2008 ◽  
Vol 64 (3-4) ◽  
pp. 451-456 ◽  
Author(s):  
H. Chaté ◽  
F. Ginelli ◽  
G. Grégoire ◽  
F. Peruani ◽  
F. Raynaud
Keyword(s):  
Collective Motion ◽  
Vicsek Model

Scaling behavior of non-equilibrium phase transitions in spontaneously ordered motion of self-propelled particles

2016 ◽  
Vol 30 (24) ◽  
pp. 1650304 ◽  
Author(s):  
R. Bakir ◽  
I. Tarras ◽  
A. Hader ◽  
H. Sbiaai ◽  
M. Mazroui ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Collective Motion ◽  
Equilibrium Phase ◽  
Deposition Process ◽  
Scaling Behavior ◽  
Scaling Exponents ◽  
Vicsek Model ◽  
Self Similar ◽  
Ordered Motion ◽  
Non Equilibrium

Many animal groups, such as bird flocks, clearly present structural order and appear to move as a single coherent entity. In interest to understand the complex behavior of these systems, many models have been proposed and tested so far. The aim of this work is to study and discuss numerically the scaling behavior in the 2D non-equilibrium phase transitions in spontaneously ordered motion of self-propelled particles in the framework of Vicsek model. This model is an important tool to study the behavior of collective motion of live biological and physical organisms. The calculation of the scaling exponents is effected by using the scaling dynamic method. However, the time evolution of the particles velocity present two different regimes separated by a cross-over time which increases linearly with both applied noise and radius of repulsive zone, but it decreases exponentially with the radius of orientation zone. The results show that the obtained exponents are similar to the growth and roughness ones used in the interfaces growth and to the submonolayer deposition process. The obtained values of these exponents are not dependent on the noises value, which proves their universality characters. Hence the kinetic evolution of the spontaneously ordered motion of self-propelled particles is self-similar. Implications of these findings are discussed.

The combined effect of attraction and orientation zones in 2D flocking models

2016 ◽  
Vol 30 (04) ◽  
pp. 1650002 ◽  
Author(s):  
Tarras Iliass ◽  
Dorilson Cambui
Keyword(s):  
Collective Motion ◽  
Numerical Study ◽  
Biological Behavior ◽  
Behavior Patterns ◽  
Vicsek Model ◽  
Agent Based ◽  
Fish Schools ◽  
Behavioral Rules ◽  
Parallel Group ◽  
Kinetic Phase Transition

In nature, many animal groups, such as fish schools or bird flocks, clearly display structural order and appear to move as a single coherent entity. In order to understand the complex motion of these systems, we study the Vicsek model of self-propelled particles (SPP) which is an important tool to investigate the behavior of collective motion of live organisms. This model reproduces the biological behavior patterns in the two-dimensional (2D) space. Within the framework of this model, the particles move with the same absolute velocity and interact locally in the zone of orientation by trying to align their direction with that of the neighbors. In this paper, we model the collective movement of SPP using an agent-based model which follows biologically motivated behavioral rules, by adding a second region called the attraction zone, where each particles move towards each other avoiding being isolated. Our main goal is to present a detailed numerical study on the effect of the zone of attraction on the kinetic phase transition of our system. In our study, the consideration of this zone seems to play an important role in the cohesion. Consequently, in the directional orientation, the zone that we added forms the compact particle group. In our simulation, we show clearly that the model proposed here can produce two collective behavior patterns: torus and dynamic parallel group. Implications of these findings are discussed.

scholarly journals Individual and Collective Information Acquisition: An Experimental Study

2021 ◽  
Author(s):  
Pellumb Reshidi ◽  
Alessandro Lizzeri ◽  
Leeat Yariv ◽  
Jimmy Chan ◽  
Wing Suen
Keyword(s):  
Experimental Study ◽  
Information Acquisition ◽  
Collective Information

scholarly journals Casimir Force between Two Vortices in a Turbulent Bose–Einstein Condensate

Atoms ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 77
Author(s):  
José Tito Mendonça ◽  
Hugo Terças ◽  
João D. Rodrigues ◽  
Arnaldo Gammal
Keyword(s):  
Casimir Force ◽  
Occupation Number ◽  
Finite Size ◽  
Condensed Medium ◽  
Einstein Condensate ◽  
Density Fluctuations ◽  
Pitaevskii Equation ◽  
Phonon Modes ◽  
Bose Einstein Condensate ◽  
Bose Einstein

We consider the Casimir force between two vortices due to the presence of density fluctuations induced by turbulent modes in a Bose–Einstein condensate. We discuss the cases of unbounded and finite condensates. Turbulence is described as a superposition of elementary excitations (phonons or BdG modes) in the medium. Expressions for the Casimir force between two identical vortex lines are derived, assuming that the vortices behave as point particles. Our analytical model of the Casimir force is confirmed by numerical simulations of the Gross–Pitaevskii equation, where the finite size of the vortices is retained. Our results are valid in the mean-field description of the turbulent medium. However, the Casimir force due to quantum fluctuations can also be estimated, assuming the particular case where the occupation number of the phonon modes in the condensed medium is reduced to zero and only zero-point fluctuations remain.

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