Statistical properties of swarms of self-propelled particles with repulsions across the order-disorder transition

Romenskyy, Maksym; Lobaskin, Vladimir

doi:10.1140/epjb/e2013-30821-1

Cited by 38 publications

(42 citation statements)

References 49 publications

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“…For P < P c , CSD can be well fitted with p(m, P ) ∼ m −γ exp(−m/m(P )) withm(P ) the characteristic cluster size at P , while for P > P c , CSD is non-monotonic and has a bump for relatively large cluster size, as shown in Fig. 14. Similar CSD behaviors below, at and above transition threshold are observed in various experimental [69] and simulation [52,[70][71][72] works of spherical ABP and SPR systems. Besides, the phase with a fat tails in the CSD appears always leading to GNF, while GNF does not always produce a fat tail.…”

Section: Density Fieldsupporting

confidence: 73%

Structure and Dynamics of a Phase-Separating Active Colloidal Fluid

2013

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We examine a minimal model for an active colloidal fluid in the form of self-propelled Brownian spheres that interact purely through excluded volume with no aligning interaction. Using simulations and analytic modeling, we quantify the phase diagram and separation kinetics. We show that this nonequilibrium active system undergoes an analog of an equilibrium continuous phase transition, with a binodal curve beneath which the system separates into dense and dilute phases whose concentrations depend only on activity. The dense phase is a unique material that we call an active solid, which exhibits the structural signatures of a crystalline solid near the crystal-hexatic transition point, and anomalous dynamics including superdiffusive motion on intermediate timescales.Active fluids composed of self-propelled units occur in nature on many scales ranging from cytoskeletal filaments and bacterial suspensions to macroscopic entities such as insects, fish and birds [1]. These systems exhibit strange and exciting phenomena such as dynamical self regulation [2], clustering [3], anomalous density fluctuations [4], unusual rheological behavior [5][6][7], and activitydependent phase boundary changes [8]. Motivated by these findings, recent experiments have focused on realizing active fluids in nonliving systems, using chemically propelled particles undergoing self-diffusophoresis [9-11], Janus particles undergoing thermophoresis [12,13], as well as vibrated monolayers of granular particles [14][15][16].In this letter we explore a minimal active fluid model: a system of self-propelled smooth spheres interacting by excluded volume alone and confined to two dimensions. Unlike self-propelled rods [18][19][20][21][22], these particles cannot interchange angular momentum and thus lack a mutual alignment mechanism. Recent simulation and experimental studies have shown that this system exhibits giant number fluctuations [23] and athermal phase separation [23,24] that are characteristic of active fluids [4,25,26]. Here we employ extensive Brownian dynamics simulations to characterize the phase diagram of this system and we develop an analytic model that captures its essential features. We show that this nonequilibrium system undergoes a continuous phase transition, analogous to that of equilibrium systems with attractive interactions, and that the phase separation kinetics demonstrate equilibrium-like coarsening. These structural and dynamic signatures of phase separation and coexistence enable an unequivocal definition of phases in this nonequilibrium, active system. Finally, we find that the dense phase is a dynamic new form of material that we call an "active solid". This material exhibits structural properties consistent with a 2D colloidal crystal near the crystal-hexatic transition point [27,28], but is characterized by such anomalous features as superdiffusive transport at intermediate timescales and a heterogeneous and dynamic stress distribution (see Fig. (1)).Model and Simulation Method : Our system consists of

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Section: Density Fieldsupporting

confidence: 73%

Structure and Dynamics of a Phase-Separating Active Colloidal Fluid

2013

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“…Here we can note that some authors suggest that even the motion of swarms of animal or human crowds follow the Newton's law, but our new law of gravity may be more appropriate in such a case [12,13].…”

Section: Determination Of the Distance Where The Coulomb Corrected Fomentioning

confidence: 89%

A Theoretical Confirmation of the Gravitation New Origin Having a Dipolar Electrical Nature with Coulomb Law Corrected

Haş¹

2015

AJMP

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Abstract:The paper starts by analyzing the actual justification of the separation existing between electrical and gravitational forces, considering that for neutral bodies the electrical interaction force at long distances r, totally cancels as equal and opposed +/-forces F C , given by Coulomb law. Initially it was demonstrated that the type of the force F D , attraction or repulsion, between two electrical dipoles, having the same orientation, is given by the variation mode of the electrical forces F C with the r distance. In this paper one demonstrates that this electrical dipole force F D may exist at any distance r, by reciprocal orientation of any two dipoles. But such dipole force F D depends on a term in 1/r 4 or greater power, being negligible compared to the gravitational force F N , which in Newton's law depends on 1/r 2 . In order to obtain the principal term in 1/r 2 , for dipole interaction F D , it was necessary and sufficiently to admit a hypothesis which considers a new Coulomb law force F CC , as a series of terms of powers of r, including a new term of the form -ln r. With this corrected Coulomb law force F CC , for dipole interaction new force F DC , an expression having the principal term in 1/r 2 results, as in Newton's law. In order to verify the above hypothesis, numerical checking for the new dipole force F DC with first 4 terms of series was performed, utilizing actual electric permeability, the constant ε 0 corrected, in all the terms. These calculations made for an astronomical distance (10 9 m), showed a good agreement (relative ratio R=F N /F DC ≈ 0.626) between the force F N given by Newton's law and the dipole force F DC obtained with the corrected Coulomb law. On the basis of this gravity theory, some important consequences result, such as the inexistence of the gravitational waves, of the black holes, of the space gravitational curvature, and of the big-bang. This gravity theory with more than 4 terms of series yield all of the four known forces in nature, so unifying them. The new dipolar gravity theory is physically possible only in quantum manifestation of the charges, and admitting the presence of a continuum media (a modern ether) as physical support of electromagnetic interactions.

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“…Understanding the interface between physics and biologically inspired algorithms is crucial towards developing 'living' computer vision systems. Recently, a new study of animal swarms has uncovered a new characteristic of their collective behavior when overcrowding sets in [180]. This study was inspired by the condensed matter models, used for example in the study of magnetism in physics.…”

Section: Resultsmentioning

confidence: 99%

Crowd behavior analysis: A review where physics meets biology

2016

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Although the traits emerged in a mass gathering are often non-deliberative, the act of mass impulse may lead to irrevocable crowd disasters. The two-fold increase of carnage in crowd since the past two decades has spurred significant advances in the field of computer vision, towards effective and proactive crowd surveillance. Computer vision studies related to crowd are observed to resonate with the understanding of the emergent behavior in physics (complex systems) and biology (animal swarm). These studies, which are inspired by biology and physics, share surprisingly common insights, and interesting contradictions. However, this aspect of discussion has not been fully explored. Therefore, this survey provides the readers with a review of the state-of-the-art methods in crowd behavior analysis from the physics and biologically inspired perspectives. We provide insights and comprehensive discussions for a broader understanding of the underlying prospect of blending physics and biology studies in computer vision.

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Statistical properties of swarms of self-propelled particles with repulsions across the order-disorder transition

Cited by 38 publications

References 49 publications

Structure and Dynamics of a Phase-Separating Active Colloidal Fluid

Structure and Dynamics of a Phase-Separating Active Colloidal Fluid

A Theoretical Confirmation of the Gravitation New Origin Having a Dipolar Electrical Nature with Coulomb Law Corrected

Crowd behavior analysis: A review where physics meets biology

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