Phase separation and large deviations of lattice active matter

Whitelam, Stephen; Klymko, Katherine; Mandal, Dibyendu

doi:10.1063/1.5023403

Cited by 81 publications

(80 citation statements)

References 69 publications

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“…Albeit the model given by Eqs. (32), (47), and (48) being no special case of the 7th-order lowdensity model, relations between the phenomenological parameters of the former model and our predictive coefficients can be established by comparing the prefactors of the terms that occur in both models. This gives, among others, the relations…”

Section: Th-order Low-density Modelmentioning

confidence: 99%

“…Due to their self-propulsion, already the common simple ABPs with a spherical shape exhibit a variety of unusual effects like accumulation at nonattracting walls [4,5,26,27], superfluidity [28], anomalous Casimir forces [29], negative interfacial tension [30], reversed Ostwald ripening [31], non-state-function pressure [32,33], and motility-induced phase separation (MIPS) [3]. The latter effect originates from the complex nonequilibrium dynamics of interacting ABPs and gained particularly strong scientific attention in recent years [21,[33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49].…”

Section: Introductionmentioning

confidence: 99%

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Predictive local field theory for interacting active Brownian spheres in two spatial dimensions

Bickmann¹,

Wittkowski²

2020

J. Phys.: Condens. Matter

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We present a predictive local field theory for the nonequilibrium dynamics of interacting active Brownian particles with a spherical shape in two spatial dimensions. The theory is derived by a rigorous coarse-graining starting from the Langevin equations that describe the trajectories of the individual particles. For maximal accuracy and generality of the theory, it includes configurational order parameters and derivatives up to infinite order. In addition, we discuss possible approximations of the theory and present reduced models that are easier to apply. We show that our theory contains popular models such as Active Model B + as special cases and that it provides explicit expressions for the coefficients occurring in these and other, often phenomenological, models. As a further outcome, the theory yields an analytical expression for the density-dependent mean swimming speed of the particles. To demonstrate an application of the new theory, we analyze a simple reduced model of the lowest nontrivial order in derivatives, which is able to predict the onset of motility-induced phase separation of the particles. By a linear stability analysis, an analytical expression for the spinodal corresponding to motility-induced phase separation is obtained. This expression is evaluated for the case of particles interacting repulsively by a Weeks-Chandler-Anderson potential. The analytical predictions for the spinodal associated with these particles are found to be in very good agreement with the results of Brownian dynamics simulations that are based on the same Langevin equations as our theory. Furthermore, the critical point predicted by our analytical results agrees excellently with recent computational results from the literature. arXiv:1909.03369v1 [cond-mat.soft] 8 Sep 2019 2 The actual particle number density or number concentration of the ABPs is given by 2πρ( r, t).

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Section: Th-order Low-density Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Predictive local field theory for interacting active Brownian spheres in two spatial dimensions

Bickmann¹,

Wittkowski²

2020

J. Phys.: Condens. Matter

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“…This has been used extensively in kinetically constrained dynamics and glassy models where promoting atypical currents leads to probe system configurations otherwise inaccessible [71][72][73][74]. In active systems, the connexion between clustering and rare fluctuations has been explored only recently, thus shedding light on phase transitions at constant activity and density [75][76][77][78].…”

Section: Phase Transitions In Biased Ensemblesmentioning

confidence: 99%

Dissipation controls transport and phase transitions in active fluids: mobility, diffusion and biased ensembles

Fodor¹,

Nemoto²,

Vaikuntanathan³

2020

New J. Phys.

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Active fluids operate by constantly dissipating energy at the particle level to perform a directed motion, yielding dynamics and phases without any equilibrium equivalent. The emerging behaviors have been studied extensively, yet deciphering how local energy fluxes control the collective phenomena is still largely an open challenge. We provide generic relations between the activity-induced dissipation and the transport properties of an internal tracer. By exploiting a mapping between active fluctuations and disordered driving, our results reveal how the local dissipation, at the basis of self-propulsion, constrains internal transport by reducing the mobility and the diffusion of particles. Then, we employ techniques of large deviations to investigate how interactions are affected when varying dissipation. This leads us to shed light on a microscopic mechanism to promote clustering at low dissipation, and we also show the existence of collective motion at high dissipation. Overall, these results illustrate how tuning dissipation provides an alternative route to phase transitions in active fluids.

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“…Lattice models have repeatedly been used as minimal models for the analysis of various aspects of active matter [66,[74][75][76][77]. For our purpose of studying the extraction of work, we consider a one-dimensional lattice with L sites, periodic boundary conditions, and one active and one passive particle, as shown in Fig.…”

Section: A Setupmentioning

confidence: 99%

Autonomous Engines Driven by Active Matter: Energetics and Design Principles

et al. 2019

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Because of its nonequilibrium character, active matter in a steady state can drive engines that autonomously deliver work against a constant mechanical force or torque. As a generic model for such an engine, we consider systems that contain one or several active components and a single passive one that is asymmetric in its geometrical shape or its interactions. Generally, one expects that such an asymmetry leads to a persistent, directed current in the passive component, which can be used for the extraction of work. We validate this expectation for a minimal model consisting of an active and a passive particle on a one-dimensional lattice. It leads us to identify thermodynamically consistent measures for the efficiency of the conversion of isotropic activity to directed work. For systems with continuous degrees of freedom, work cannot be extracted using a one-dimensional geometry under quite general conditions. In contrast, we put forward two-dimensional shapes of a movable passive obstacle that are best suited for the extraction of work, which we compare with analytical results for an idealised work-extraction mechanism. For a setting with many noninteracting active particles, we use a mean-field approach to calculate the power and the efficiency, which we validate by simulations. Surprisingly, this approach reveals that the interaction with the passive obstacle can mediate cooperativity between otherwise noninteracting active particles, which enhances the extracted power per active particle significantly. arXiv:1905.00373v2 [cond-mat.stat-mech]

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Phase separation and large deviations of lattice active matter

Cited by 81 publications

References 69 publications

Predictive local field theory for interacting active Brownian spheres in two spatial dimensions

Predictive local field theory for interacting active Brownian spheres in two spatial dimensions

Dissipation controls transport and phase transitions in active fluids: mobility, diffusion and biased ensembles

Autonomous Engines Driven by Active Matter: Energetics and Design Principles

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