Dynamics of a homogeneous active dumbbell system

Suma, Antonio; Gonnella, Giuseppe; Laghezza, Gianluca; Lamura, A.; Mossa, Alessandro; Cugliandolo, Leticia F.

doi:10.1103/physreve.90.052130

Cited by 42 publications

(87 citation statements)

References 87 publications

(185 reference statements)

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“…Therefore it would be very interesting to see if the entropy production description also applies to passive-AOUP mixtures or to what extent this would be violated by the non-Boltzmann distribution of the AOUPs. Another interesting and possibly relevant extension would be to incorporate velocity correlations along the chain [38].Consistent with symmetry considerations (SM), our data suggest that the entropy production scales asṠ ∼ γχ 2 M N for small χ. Entropy produced on the relevant microscopic timescale γ −1 i.e. S ∼ χ 2 M N competes with the mixing entropy proportional to T M only.…”

supporting

confidence: 81%

Small Activity Differences Drive Phase Separation in Active-Passive Polymer Mixtures

2017

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Recent theoretical studies found that mixtures of active and passive colloidal particles phase separate but only at very high activity ratio. The high value poses serious obstacles for experimental exploration of this phenomenon. Here we show using simulations that when the active and passive particles are polymers, the critical activity ratio decreases with the polymer length. This not only facilitates the experiments but also has implications on the DNA organization in living cell nuclei. Entropy production can be used as an accurate indicator of this non-equilibrium phase transition.PACS numbers: 64.75. Va, 87.15.Zg, 05.70.Ln Active matter consists of microscopic constituents, such as bacteria, micro-swimmers or molecular motors that transform energy from the surroundings or their own sources into mechanical work. The energy is fed into the system on the particle scale producing local spatiotemporal gradients which give rise to a number of interesting macroscopic non-equilibrium phenomena such as emergence of spatial structures through dynamical phase transitions [1], directed rotational motion [2], propagating waves [3,4] and phase separation of mixtures of active and passive particles with purely repulsive interactions [5][6][7][8][9][10].The latter phenomenon, that we focus on here, is particularly interesting as often the active particles reside in a passive environment or the level of their activity is heterogeneous. Moreover, the mixture of active and passive polymers was hypothesised to play a role in the DNA organization within the cell nucleus during the interphase (metabolic phase of the cells life) [11][12][13]. Indeed, DNA transcription or the hypothesised active loop extrusion [14] involve continual energy influx and dissipation on microscopic length scales. Observations of living cells [15,16] and the "C-experiments" [17] confirm that euchromatin -the active DNA, is colocalized and separated from the inactive denser heterochromatin by an unknown mechanism. The chemical difference of the hetero-and euchromatin [16] could play a role in the chromatin separation [18], and, as first shown by Ganai et al [11], the active process that we are focusing on here too, could bring an additional contribution to the separation.Recently, two works [6, 10] modelled active colloidal particles as having higher diffusivity as their passive counterparts, by simply connecting them to a higher temperature thermostat. Both, simulations and analytical theory predict phase separation at a temperature ratio of about 30. Similarly, high critical activity contrast is observed also for other, "vectorial" activity models such as active Brownian particles (ABP) [5] (Péclet number over 50) and Vicsek model [9,19] where the generated force or velocity acting on the particle has a specific direction that randomises on longer time scales. These models are more complex due to other effects like pressure dependence on the interaction details of the particles with the container [20][21][22]. Thus we here restrict ourselves to the...

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supporting

confidence: 81%

Small Activity Differences Drive Phase Separation in Active-Passive Polymer Mixtures

2017

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“…Therefore, the scaling with persistence time at finite density is qualitatively different from the linear behaviour found in the dilute regime. In a model of repulsive active dumbbells studied recently in the fluid regime, T eff has a non-monotonic dependence on the activity that becomes more pronounced by increasing the density [18]. In our model, many-body effects alter the scaling of T eff with τ in a simpler manner, monotonically reducing the effective "heating" of the system.…”

mentioning

confidence: 87%

“…This question is natural because if some mapping to an equilibrium situation exists, then the whole arsenal of equilibrium statistical mechanics becomes available for further theoretical treatment. In particular the definition of a non-equilibrium temperature [13][14][15][16][17][18], of an active pressure [8,19,20], of activityinduced interactions [8,21] and non-equilibrium free energies [22,23] have been investigated for self-propelled particles. …”

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confidence: 99%

“…The simple fluid state has been analysed mostly by numerical simulations determining fluctuation-dissipation relations for different observables in various models of self-propelled particles [13,15,18]. Finally, in the limit of very large densities where self-propelled particles may undergo a non-equilibrium glass transition, the driven glassy dynamics should resemble the one of slowly driven glasses and a collective effective temperature was predicted to emerge from the analysis of a mean-field active glass model [31], but this prediction has not been tested in a rep-1 alistic model in finite dimension.…”

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confidence: 99%

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From single-particle to collective effective temperatures in an active fluid of self-propelled particles

Levis¹,

Berthier²

2015

EPL

101

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-We present a comprehensive analysis of effective temperatures based on fluctuationdissipation relations in a model of an active fluid composed of self-propelled hard disks. We first investigate the relevance of effective temperatures in the dilute and moderately dense fluids. We find that a unique effective temperature does not in general characterize the non-equilibrium dynamics of the active fluid over this broad range of densities, because fluctuation-dissipation relations yield a lengthscale-dependent effective temperature. By contrast, we find that the approach to a non-equilibrium glass transition at very large densities is accompanied by the emergence of a unique effective temperature shared by fluctuations at all lengthscales. This suggests that an effective thermal dynamics generically emerges at long times in very dense suspensions of active particles due to the collective freezing occurring at non-equilibrium glass transitions.Introduction. -Statistical mechanics provides a unified theoretical description of systems at thermal equilibrium in terms of the probability distribution over phase space, from which thermodynamic quantities such as temperature can be defined [1]. A similar framework is lacking for out-of-equilibrium systems for which the definition of a temperature remains an open issue [2]. Active matter formed by assemblies of living cells [3], bacteria [4], selfpropelled colloids [5][6][7][8] or grains [9,10], is a coherent class of non-equilibrium systems receiving increasing attention, because they raise fundamental issues and for potential applications in soft matter and biophysics [11,12]. A number of recent studies have addressed the question of whether "effective" thermodynamic concepts can be fruitfully applied to describe the phase behaviour and microscopic dynamics of active matter. This question is natural because if some mapping to an equilibrium situation exists, then the whole arsenal of equilibrium statistical mechanics becomes available for further theoretical treatment. In particular the definition of a non-equilibrium temperature [13][14][15][16][17][18], of an active pressure [8,19,20], of activityinduced interactions [8,21] and non-equilibrium free energies [22,23] have been investigated for self-propelled particles.

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“…1. It consists of N identical self-propelled dumbbells [5,[20][21][22][23][24][25][26] . A mobile wall of thickness e 2 separates this area into two non-communicating chambers.…”

Section: -Description Of the Modelmentioning

confidence: 99%

Pressure of a gas of underdamped active dumbbells

Joyeux

Bertin

2016

Phys. Rev. E

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Abstract:The pressure exerted on a wall by a gas at equilibrium does not depend on the shape of the confining potential defining the walls. In contrast, it has been shown recently [A.P. Solon et.al., Nat. Phys. 11, 673 (2015)] that a gas of overdamped active particles exerts on a wall a force that depends on the confining potential, resulting in a net force on an asymmetric wall between two chambers at equal densities. Here, considering a model of underdamped self-propelled dumbbells in two dimensions, we study how the behavior of the pressure depends on the damping coefficient of the dumbbells, thus exploring inertial effects.We find in particular that the force exerted on a moving wall between two chambers at equal density continuously vanishes at low damping coefficient, and exhibits a complex dependence on the damping coefficient at low density, when collisions are scarce. We further show that this behavior of the pressure can to a significant extent be understood in terms of the trajectories of individual particles close to and in contact with the wall. 02.70.Ns (Molecular dynamics and particle methods) (#)

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Dynamics of a homogeneous active dumbbell system

Cited by 42 publications

References 87 publications

Small Activity Differences Drive Phase Separation in Active-Passive Polymer Mixtures

Small Activity Differences Drive Phase Separation in Active-Passive Polymer Mixtures

From single-particle to collective effective temperatures in an active fluid of self-propelled particles

Pressure of a gas of underdamped active dumbbells

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