Hidden velocity ordering in dense suspensions of self-propelled disks

Caprini, Lorenzo; Marconi, U.; Maggi, Claudio; Paoluzzi, Matteo; Puglisi, Andrea

doi:10.1103/physrevresearch.2.023321

Cited by 102 publications

(138 citation statements)

References 85 publications

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“…These domains have been observed numerically in Ref. [32] in two-dimensional systems of repulsive self-propelled disks [active Brownian particles (ABP)] both at moderate packing fraction in the phase-coexistence region and at large packing fraction in homogeneous active liquid, hexatic, and solid phases [33], where domains with aligned velocities can still be observed [34].…”

Section: Introductionmentioning

confidence: 82%

“…To characterize the size of the velocity domains, we study the spatial velocity correlation functions v(x)v(0) in the steady-state adapting the strategy of Ref. [34] to a onedimensional system. In this simple one-dimensional case, v(x)v(0) can be analytically predicted in the active harmonic crystal approximation, as shown in Appendix C. We find that, in the stationary regime, the fluctuation amplitude of each velocity mode has the following shape:…”

Section: A Spatial Velocity and Energy Correlationsmentioning

confidence: 99%

“…A nonequilibrium phase activity-density diagram has been introduced to represent both homogeneous and inhomogeneous regimes [34] and the structural properties of the system have been compared with the typical size of the aligned domains. The model reproduces several experimental results regarding confluent cell monolayers [35][36][37][38], whose velocity fields display alignment patterns quite similar to the corresponding predictions of the ABP model.…”

Section: Introductionmentioning

confidence: 99%

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Time-dependent properties of interacting active matter: Dynamical behavior of one-dimensional systems of self-propelled particles

Caprini

Marconi

2020

Phys. Rev. Research

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We study an interacting high-density one-dimensional system of self-propelled particles described by the active Ornstein-Uhlenbeck particle model where, even in the absence of alignment interactions, velocity and energy domains spontaneously form in analogy with those already observed in two dimensions. Such domains are regions where the individual velocities are spatially correlated as a result of the interplay between self-propulsion and interactions. Their typical size is controlled by a characteristic correlation length. In this work, we focus on a lesser-known aspect of the model, namely, its dynamical behavior. To this purpose, we investigate theoretically and numerically the time-dependent velocity autocorrelation and spatiotemporal velocity correlation functions. The study of these correlations provides a measure of the average lifetime and, thus, the stability in time of the velocity domains.

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Section: Introductionmentioning

confidence: 82%

Section: A Spatial Velocity and Energy Correlationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Time-dependent properties of interacting active matter: Dynamical behavior of one-dimensional systems of self-propelled particles

Caprini

Marconi

2020

Phys. Rev. Research

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“…Its connection with other popular models for self-propelled particles has been addressed by some authors [51,52]. For instance, the AOUP model can reproduce the accumulation near the boundaries of channels and obstacles [41,53], the non-equilibrium clustering or phase-separation [25,54,55] typical of active matter and the spatial velocity correlation spontaneously observed in dense active systems [56,57]. According to the AOUP scheme, the position in d dimensions x of the self-propelled particle evolves with the following stochastic equation,…”

Section: Self-propelled Particlesmentioning

confidence: 99%

Fluctuation–Dissipation Relations in Active Matter Systems

2021

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We investigate the non-equilibrium character of self-propelled particles through the study of the linear response of the active Ornstein–Uhlenbeck particle (AOUP) model. We express the linear response in terms of correlations computed in the absence of perturbations, proposing a particularly compact and readable fluctuation–dissipation relation (FDR): such an expression explicitly separates equilibrium and non-equilibrium contributions due to self-propulsion. As a case study, we consider non-interacting AOUP confined in single-well and double-well potentials. In the former case, we also unveil the effect of dimensionality, studying one-, two-, and three-dimensional dynamics. We show that information about the distance from equilibrium can be deduced from the FDR, putting in evidence the roles of position and velocity variables in the non-equilibrium relaxation.

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“…Studies on single-particle dynamics [31] and jamming transition [19,32,33] have also been extended for active systems. The current consensus in the field is that activity pushes the glass and jamming transitions to lower temperature or higher density, though the nature of an active glass seems to be qualitatively similar to an equilibrium glass and the difference lies in the quantitative description, such as in the form of long-ranged velocity correlation [30,34] or the evolving effective temperature, T ef f , much like a sheared system [25,26]. However, this apparent similarity of glassy dynamics in an active and equilibrium system is somewhat puzzling as activity is known to exhibit nontrivial behavior, such as flocking [35] or giant number fluctuation [17,18,36,37] in a dilute system, and calls for rigorous theoretical exploration of the problem.…”

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confidence: 99%

Dynamic heterogeneity in active glass-forming liquids is qualitatively different compared to its equilibrium behaviour

Paul

Nandi

Karmakar

2021

Preprint

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Activity driven glassy dynamics is ubiquitous in collective cell migration,intracellular transport, dynamics in bacterial and ants colonies as well as artificially driven synthetic systems such as vibrated granular materials, etc. Active glasses are hitherto assumed to be qualitatively similar to their equilibrium counterparts at a suitably defined effective temperature, ff. Combining large-scale simulations with analytical mode-coupling theory for such systems, we show that, in fact, an active glass is qualitatively different from an equilibrium glassy system. Although the relaxation dynamics can be similar to an equilibrium system at a ff, effects of activity on the dynamic heterogeneity (DH), which has emerged as a cornerstone of glassy dynamics, is quite nontrivial and complex. In particular, active glasses show dramatic growth of DH, and systems with similar relaxation time and ff can have widely varying DH. Comparison of our non-equilibrium extended mode-coupling theory for such systems with simulation results show that the theory captures the basic characteristics of such systems. Our study raises fundamental questions on the supposedly central role of DH in controlling the relaxation dynamics in a glassy system and can have important implications even for the equilibrium glassy dynamics.

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Hidden velocity ordering in dense suspensions of self-propelled disks

Cited by 102 publications

References 85 publications

Time-dependent properties of interacting active matter: Dynamical behavior of one-dimensional systems of self-propelled particles

Time-dependent properties of interacting active matter: Dynamical behavior of one-dimensional systems of self-propelled particles

Fluctuation–Dissipation Relations in Active Matter Systems

Dynamic heterogeneity in active glass-forming liquids is qualitatively different compared to its equilibrium behaviour

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