Article
Mechanics
Miguel Angel Lopez-Castano, Alejandro Marquez Seco, Alicia Marquez Seco, Alvaro Rodriguez-Rivas, Francisco Vega Reyes
Summary: We studied the velocity autocorrelations in confined two-dimensional active rotors (disks). Small scale oscillations were observed in both rotational and translational velocity autocorrelations, with the characteristic frequency increasing as rotational activity increased. At stronger particle rotational activity, large scale particle spin fluctuations tended to vanish, while small oscillations around zero persisted, and spins remained predominantly and strongly anti-correlated at longer times. For weaker rotational activity, spin fluctuations became larger, and angular velocities remained de-correlated at longer times. The autocorrelation oscillations were found to be related to the rotational activity and indicative of the emergence of chirality in the dynamics of the particulate system.
Article
Chemistry, Multidisciplinary
Zhihan Chen, Hongru Ding, Pavana Siddhartha Kollipara, Jingang Li, Yuebing Zheng
Summary: Researchers propose a novel optical feedback control system that can mimic collective motion observed in living objects. This system allows for experimental investigation of velocity alignment in a perturbed environment, and spontaneous formation of different moving states and dynamic transitions were observed.
ADVANCED MATERIALS
(2023)
Article
Mechanics
Pawan Kumar Mishra, Shradha Mishra
Summary: In this study, a collection of self-propelled polar particles with birth and death behavior is investigated through modeling and calculations. The system undergoes a transition from disorder to order with temperature tuning, and a crossover from first order to continuous transition is observed by adjusting the birth and death parameter. The dependence of the nature of phase transition on the birth and death parameter is confirmed through perturbative calculation of the effective free energy.
Article
Chemistry, Physical
Francis Jose, Shalabh K. Anand, Sunil P. Singh
Summary: The study investigates the impact of concentration-dependent motility on the phase separation and dynamics of colloids, revealing that the system can phase separate at very low packing fractions at higher self-propulsion speeds. In the phase-separated regime, the effective diffusivity shows a crossover behavior with the self-propulsion speed, and decreases exponentially with packing fraction.
Article
Physics, Multidisciplinary
Prashant Singh, Anupam Kundu
Summary: The study examines the motion of tagged particles in a harmonic chain of active particles, considering three different active particle dynamics models. It demonstrates a crossover in mean squared displacement from super-diffusive to sub-diffusive scaling and explains it with appropriate crossover functions. Furthermore, interesting scaling forms of equal and unequal time autocorrelation and cross-correlations are found in appropriate limits of observation time.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2021)
Article
Physics, Fluids & Plasmas
Elena Sese-Sansa, Demian Levis, Ignacio Pagonabarraga
Summary: In this study, a model system of repulsive self-propelled disks in two dimensions with ferromagnetic and nematic velocity alignment interactions is comprehensively analyzed. It is found that strong alignment leads to orientational order, while moderate alignment with high self-propulsion results in motility-induced phase separation (MIPS). The microscopic theory derived for these systems accurately predicts the occurrence of MIPS, showing the predictive power of such theories in describing complex active matter systems.
Article
Physics, Fluids & Plasmas
Ydan Ben Dor, Sunghan Ro, Yariv Kafri, Mehran Kardar, Julien Tailleur
Summary: We found that disordered boundaries disrupt bulk phase separation in scalar active systems in dimensions less than the critical dimension d(c) = 3. This is in contrast to the equilibrium case where boundaries have no impact on bulk phase-separated systems. Long-range correlations of the density field and a cascade of eddies prevent bulk phase separation in low dimensions.
Article
Physics, Fluids & Plasmas
Diego M. Fieguth, Timo Schlachter, Daniel S. Brady, James R. Anglin
Summary: This study examines a Hamiltonian system representing an active particle that can move in noisy and dissipative environments by drawing energy from an internal depot. Despite energy dissipation to the environment, it can help stabilize the dynamic process of the active particle.
Article
Physics, Multidisciplinary
G. Fausti, E. Tjhung, M. E. Cates, C. Nardini
Summary: In passive fluid-fluid phase separation, a single interfacial tension governs both capillary fluctuations of the interface and the rate of Ostwald ripening. However, in active systems, these phenomena are governed by two different tensions, and strong enough activity can result in negative capillary tension for interfacial fluctuations. Depending on the global composition, the system can self-organize into either a microphase-separated state with inhibited coalescence, or an active foam state.
PHYSICAL REVIEW LETTERS
(2021)
Article
Chemistry, Physical
Lorenzo Caprini, Alexander R. Sprenger, Hartmut Loewen, Rene Wittmann
Summary: We propose a new model that generates a complete family of descendants flexibly. This model unifies two commonly used models for active matter, revealing a deep stochastic relationship between them. It provides more suitable models for various active matter systems and explains their characteristic distribution features. We evaluate the model in a reference example and demonstrate the transition in the shape of positional density distribution.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Review
Mechanics
Ilham Essafri, Bappa Ghosh, Caroline Desgranges, Jerome Delhommelle
Summary: This article reviews recent advances in the design, synthesis, and modeling of active fluids, highlighting the development of biomimetic nano- and micro-machines and swimmers inspired by biological systems. The study of these far-from-equilibrium systems has brought about new simulation methods and theoretical models in nonequilibrium physics. These advancements have paved the way for the design, synthesis, and modeling of autonomous systems at the nano- and micro-scale and the development of soft matter robotics.
Article
Chemistry, Physical
Federico Fadda, Daniel A. A. Matoz-Fernandez, Rene van Roij, Sara Jabbari-Farouji
Summary: Many motile microorganisms communicate with each other and their environments through chemical signaling and self-generated chemical gradients. The interplay between crowding and chemotactic interactions on their collective behavior remains poorly understood. In this study, we use simulations to investigate the effect of packing fraction on the formation of non-equilibrium structures in a monolayer of diffusiophoretic self-propelled colloids. We observe a new phase-separated state resulting from a competition between long-range diffusiophoretic interactions and motility.
Article
Physics, Multidisciplinary
R. A. KoPP, S. H. L. Klapp
Summary: Based on Brownian dynamics simulations, this study investigates the collective behavior of two-dimensional system of repulsively interacting colloidal particles propelled by a repulsive feedback force with time delay. Despite purely isotropic pair interactions, a spontaneous, large-scale alignment of velocity vectors is observed, persisting for long times without steady-state clustering. The observations are explained by the combined effect of steric interactions yielding local velocity ordering and the effect of time delay generating cluster dissolution, velocity persistence, and large distance velocity alignment. Overall, the behavior shows interesting similarities, as well as differences, with those observed in models of active matter such as active Brownian particles and the Vicsek model.
Article
Physics, Multidisciplinary
Umberto Marini Bettolo Marconi, Lorenzo Caprini, Andrea Puglisi
Summary: Researchers derived the hydrodynamics for a system of N active, spherical, underdamped particles, considering density, polarization, velocity, and kinetic temperature fields, and predicting spatial equal-time velocity correlations in active liquids. In active liquids, the correlation length of transverse velocity fluctuations is significantly shorter than that of longitudinal fluctuations, with the latter depending on sound speed and persistence time, while the former shows weaker dependence on these parameters. They also derived the dynamical structure factors and intermediate scattering functions within the same framework, finding that velocity decorrelates on a much longer time-scale compared to passive fluids.
NEW JOURNAL OF PHYSICS
(2021)
Article
Physics, Fluids & Plasmas
Koushik Goswami
Summary: We study the underdamped motion of a passive particle in an active environment using the phase space path integral method. The probability distribution function of position and velocity for a free and a harmonically bound particle is derived. Two similar OUP models are considered to investigate the effects of inertia and other parameters on the particle dynamics. The work fluctuations of a harmonically trapped particle are also analyzed, and the fluctuation theorem of work is validated with an effective temperature in the steady-state limit.
Article
Biology
Colin R. Twomey, Andrew T. Hartnett, Matthew M. G. Sosna, Pawel Romanczuk
Summary: Collective systems in nature are made up of many interacting individuals, producing large-scale coordinated behavior. However, existing measures of coordination are system-specific, making broad comparisons challenging. By using an information-theoretic measure of multivariate dependence, a system-independent measure of coordination can be identified, facilitating the understanding of intrasystem organizational structure.
THEORY IN BIOSCIENCES
(2021)
Article
Multidisciplinary Sciences
Zahra Alirezaeizanjani, Robert Grossmann, Veronika Pfeifer, Marius Hintsche, Carsten Beta
Article
Biology
Jolle W. Jolles, Nils Weimar, Tim Landgraf, Pawel Romanczuk, Jens Krause, David Bierbach
Article
Multidisciplinary Sciences
Robert Grossmann, Igor S. Aranson, Fernando Peruani
NATURE COMMUNICATIONS
(2020)
Article
Biochemical Research Methods
Pascal P. Klamser, Pawel Romanczuk
Summary: Research shows that animal collectives perform optimally at criticality, not due to optimal collective response but due to the emergent group structure. Strong spatial self-sorting effects at the critical point lead to strong selection gradients, making it an evolutionary unstable state.
PLOS COMPUTATIONAL BIOLOGY
(2021)
Article
Physics, Multidisciplinary
Parisa Rahmani, Fernando Peruani, Pawel Romanczuk
Summary: The study reveals that in active systems with topological interactions, spatial heterogeneities can maintain long-range order and enhance the emergence of traveling bands. Topological flocking models in heterogeneous environments exhibit features similar to metric models, with spatial heterogeneities inducing an effective density-order coupling that facilitates the emergence of traveling bands.
COMMUNICATIONS PHYSICS
(2021)
Article
Physics, Multidisciplinary
Niklas H. Kitzmann, Pawel Romanczuk, Nico Wunderling, Jonathan F. Donges
Summary: Only through a fast and global transformation towards decarbonization and sustainability can the Earth be maintained in a civilization-friendly state. Cities, as hotspots for (green) innovation and experimentation, play a crucial role in this transition. They can be seen as nodes in a globe-spanning learning network.
EUROPEAN PHYSICAL JOURNAL-SPECIAL TOPICS
(2022)
Article
Physics, Multidisciplinary
Eduardo Moreno, Robert Grossmann, Carsten Beta, Sergio Alonso
Summary: This study extends the previous single cell motility model to describe the collective motion of large populations of interacting amoebae, revealing that increasing cell density decreases cell motility due to the formation of cell clusters.
FRONTIERS IN PHYSICS
(2022)
Article
Physics, Applied
Valeriia Muraveva, Marek Bekir, Nino Lomadze, Robert Grossmann, Carsten Beta, Svetlana Santer
Summary: This article reports on a system that uses thermo-osmotic and diffusio-osmotic mechanisms to generate opposing flows in microfluidics. By adjusting the laser intensity, the liquid flow can be reversibly switched from outward to inward, allowing for precise transport of particles to desired locations. This optofluidic system demonstrates a high degree of controllability and opens up innovative possibilities for advanced microfluidic applications.
APPLIED PHYSICS LETTERS
(2022)
Article
Multidisciplinary Sciences
Winnie Poel, Bryan C. Daniels, Matthew M. G. Sosna, Colin R. Twomey, Simon P. Leblanc, Iain D. Couzin, Pawel Romanczuk
Summary: The study finds that startle cascades in fish schools are subcritical and that the distance to criticality decreases as perceived risk increases. Considering the costs associated with both true and false alarms, being subcritical and modulating the distance to criticality can be understood as managing a trade-off between sensitivity and robustness based on the riskiness and noisiness of the environment.
Article
Engineering, Multidisciplinary
David Bierbach, Luis Gomez-Nava, Fritz A. Francisco, Juliane Lukas, Lea Musiolek, Verena V. Hafner, Tim Landgraf, Pawel Romanczuk, Jens Krause
Summary: Through experimental research, it was found that live fish can anticipate the actions of a robot, including its final destination and turning movements, and can adaptively change their own behavior. This suggests that anticipation in fish may have evolved as a mechanism to adapt to different social interaction partners.
BIOINSPIRATION & BIOMIMETICS
(2022)
Article
Physics, Multidisciplinary
Luis Gomez-Nava, Robert T. Lange, Pascal P. Klamser, Juliane Lukas, Lenin Arias-Rodriguez, David Bierbach, Jens Krause, Henning Sprekeler, Pawel Romanczuk
Summary: Groups of animals exhibit coordinated collective behaviors that benefit individuals through social information exchange and protection. The study finds that collective dive cascades in fish shoals resemble a stochastic excitable system, suggesting that they operate at a critical point between high individual activity and low overall activity. The best fitting model at the critical point allows effective propagation of external perturbations, such as predator attacks, indicating that criticality may be a plausible principle for information processing in large animal collectives.
Article
Biology
Juliane Lukas, Jens Krause, Arabella Sophie Traeger, Jonas Marc Piotrowski, Pawel Romanczuk, Henning Sprekeler, Lenin Arias-Rodriguez, Stefan Krause, Christopher Schutz, David Bierbach
Summary: Collective behaviour in multi-species fish shoals can provide antipredator benefits. The presence of multiple species offers an opportunity to study the evolution of collective behaviour. This study found that mixed-species fish shoals performing collective dives can generate water waves that reduce predator attacks. The behaviour of the species in the shoal influences the overall effectiveness of wave production.
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
(2023)
Article
Biochemistry & Molecular Biology
Petro Sarkanych, Mariana Krasnytska, Luis Gomez-Nava, Pawel Romanczuk, Yurij Holovatch
Summary: In this paper, the spin model for collective decision making among higher organisms is reconsidered. The authors provide a statistical physics interpretation of the model and find exact solutions for its thermodynamics on a complete graph. Individual-based simulations confirm the analytical predictions and also shed light on the impact of system size and initial conditions on the convergence of collective decision making.
Article
Physics, Fluids & Plasmas
Yinong Zhao, Thomas Ihle, Zhangang Han, Cristian Huepe, Pawel Romanczuk
Summary: This study investigates a group of self-propelled particle models that achieve collective motion through alignment-based dynamics, analyzing their phase space across a range of parameters. The study compares models with and without repulsive interactions, identifying differences and previously uncharacterized regimes. The results suggest deviations from theoretical predictions may be attributed to remaining inhomogeneities or finite-size effects, providing a comprehensive perspective on the phases and states in alignment-based self-propelled particle models.