Mesoscopic theory for fluctuating active nematics

Bertin, Éric; Chaté, Hugues; Ginelli, Francesco; Mishra, Sudhanshu; Peshkov, Anton; Ramaswamy, Sriraṁ

doi:10.1088/1367-2630/15/8/085032

Cited by 125 publications

(217 citation statements)

References 47 publications

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205

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“…This accounts for the curvature in the nematic order inducing a local polarity, and produces phase separation [34,35]. We obtain concentration ordering without the addition of this term or any free energy terms.…”

Section: Concentration Segregationmentioning

confidence: 97%

Intrinsic free energy in active nematics

Thampi¹,

Doostmohammadi²,

Golestanian

et al. 2015

EPL

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Basing our arguments on the theory of active liquid crystals, we demonstrate both analytically and numerically, that the activity can induce an effective free energy which enhances ordering in extensile systems of active rods and in contractile suspensions of active discs. We argue that this occurs because any ordering fluctuation is enhanced by the flow field it produces. A phase-diagram in the temperature-activity plane compares ordering due to a thermodynamic free energy to that resulting from the activity. We also demonstrate that activity can drive variations in concentration, but for a different physical reason that relies on the separation of hydrodynamic and diffusive timescales.

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Section: Concentration Segregationmentioning

confidence: 97%

Intrinsic free energy in active nematics

Thampi¹,

Doostmohammadi²,

Golestanian

et al. 2015

EPL

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“…Active nematics exhibit a complex spatiotemporal behavior [18] and even a long-range ordering of topological defects [19]. A theoretical understanding of active nematics was achieved by particle simulations [20], phenomenological hydrodynamic models [21,22], or by asymptotic reduction of the probabilistic Boltzmann equation for interacting particles to the Ginzburg-Landau-type model [23,24]. An equilibrium nematic liquid crystal (LC) model [25,26] supplemented by a phenomenological active stress was used in a number of works [27][28][29][30][31].…”

Section: Introductionmentioning

confidence: 99%

Topological Defects in a Living Nematic Ensnare Swimming Bacteria

et al. 2017

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Active matter exemplified by suspensions of motile bacteria or synthetic self-propelled particles exhibits a remarkable propensity to self-organization and collective motion. The local input of energy and simple particle interactions often lead to complex emergent behavior manifested by the formation of macroscopic vortices and coherent structures with long-range order. A realization of an active system has been conceived by combining swimming bacteria and a lyotropic liquid crystal. Here, by coupling the well-established and validated model of nematic liquid crystals with the bacterial dynamics, we develop a computational model describing intricate properties of such a living nematic. In faithful agreement with the experiment, the model reproduces the onset of periodic undulation of the director and consequent proliferation of topological defects with the increase in bacterial concentration. It yields a testable prediction on the accumulation of bacteria in the cores of þ1=2 topological defects and depletion of bacteria in the cores of −1=2 defects. Our dedicated experiment on motile bacteria suspended in a freestanding liquid crystalline film fully confirms this prediction. Our findings suggest novel approaches for trapping and transport of bacteria and synthetic swimmers in anisotropic liquids and extend a scope of tools to control and manipulate microscopic objects in active matter.

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“…[6] that includes the effects of the nonlinearities and noises should directly apply here. Lastly, dry active matters are characterised by density segregation in the steady states [43,44]. Our linearised treatment is unable to capture this.…”

Section: B Intermediate Frictionmentioning

confidence: 99%

Role of interfacial friction for flow instabilities in a thin polar-ordered active fluid layer

Sarkar

Basu

2015

Phys. Rev. E

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We construct a generic coarse-grained dynamics of a thin inflexible planar layer of polar-ordered suspension of active particles, that is frictionally coupled to an embedding isotropic passive fluid medium with a friction coefficient Γ. Being controlled by Γ, our model provides a unified framework to describe the long wavelength behaviour of a variety of thin polar-ordered systems, ranging from wet to dry active matters and free standing active films. Investigations of the linear instabilities around a chosen orientationally ordered uniform reference state reveal generic moving and static instabilities in the system, that can depend sensitively on Γ. Based on our results, we discuss estimation of bounds on Γ in experimentally accessible systems.

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Mesoscopic theory for fluctuating active nematics

Cited by 125 publications

References 47 publications

Intrinsic free energy in active nematics

Intrinsic free energy in active nematics

Topological Defects in a Living Nematic Ensnare Swimming Bacteria

Role of interfacial friction for flow instabilities in a thin polar-ordered active fluid layer

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