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Geometric confinement and topological constraints present promising means of controlling active materials. By combining analytical arguments derived from the Born-Oppenheimer approximation with numerical simulations, we investigate the…

Soft Condensed Matter · Physics 2023-10-11 Farzan Vafa , David R. Nelson , Amin Doostmohammadi

We study the dynamics of topological defects in active nematic films with spatially-varying activity and consider two setups: i) a constant activity gradient, and ii) a sharp jump in activity. A constant gradient of extensile (contractile)…

Soft Condensed Matter · Physics 2022-09-02 Jonas Rønning , M. Cristina Marchetti , Luiza Angheluta

We investigate the ground state configurations of $p$-atic liquid crystals on fixed curved surfaces. We focus on the intrinsic geometry and show that isothermal coordinates are particularly convenient as they explicitly encode a geometric…

Soft Condensed Matter · Physics 2022-08-31 Farzan Vafa , Grace H. Zhang , David R. Nelson

We study the spatiotemporal patterns that emerge when an active nematic film is topologically constraint. These topological constraints allow to control the non-equilibrium dynamics of the active system. We consider ellipsoidal shapes for…

Soft Condensed Matter · Physics 2017-03-13 Francesco Alaimo , Christian Köhler , Axel Voigt

Inspired by epithelial morphogenesis, we consider a minimal model for the shaping of a surface driven by $p$-atic topological defects. We show that a positive (negative) defect can dynamically generate a (hyperbolic) cone whose shape…

Soft Condensed Matter · Physics 2023-03-02 Farzan Vafa , L. Mahadevan

Topological defects in systems with liquid-crystalline order are crucial in determining their large-scale properties. In active systems, they are known to have properties impossible at equilibrium: for example, $+1/2$ defects in…

Soft Condensed Matter · Physics 2026-02-17 Giacomo Marco La Montagna , Sumeja Burekovic , Ananyo Maitra , Cesare Nardini

As a method for controlling active materials, researchers have suggested designing patterns of activity on a substrate, which should guide the motion of topological defects. To investigate this concept, we model the behavior of a single…

Soft Condensed Matter · Physics 2021-02-10 Xingzhou Tang , Jonathan V. Selinger

In pulsating active matter, topological defects are motile despite the absence of any macroscopic flows and microscopic self-propulsion. We reveal that this motility arises from a ratchet effect: the mechanochemical coupling between local…

Soft Condensed Matter · Physics 2026-05-26 Luca Casagrande , Alessandro Manacorda , Etienne Fodor

Inspired by recent experiments that highlight the role of nematic defects in the morphogenesis of epithelial tissues, we develop a minimal framework to study the dynamics of an active curved surface driven by its nematic texture. Allowing…

Soft Condensed Matter · Physics 2022-09-14 Farzan Vafa , L. Mahadevan

We consider active nematodynamics on deformable surfaces. Based on a thermodynamically consistent surface Beris-Edwards model we add nematic activity and focus on the emerging additional coupling mechanism between the nematic field, the…

Soft Condensed Matter · Physics 2024-05-24 Ingo Nitschke , Axel Voigt

We develop an approximate, analytical model for the velocity of defects in active nematics by combining recent results for the velocity of topological defects in nematic liquid crystals with the flow field generated from individual defects…

Soft Condensed Matter · Physics 2024-11-27 Cody D. Schimming , C. J. O. Reichhardt , C. Reichhardt

To enhance the understanding of the behavior of active nematic, it is important to understand the behavior of topological defects. In this paper, we study the configuration of topological defects of a two-dimensional active nematic around a…

Soft Condensed Matter · Physics 2026-02-16 Hiroki Matsukiyo , Jun-ichi Fukuda

We formulate the statistical dynamics of topological defects in the active nematic phase, formed in two dimensions by a collection of self-driven particles on a substrate. An important consequence of the non-equilibrium drive is the…

Soft Condensed Matter · Physics 2018-09-12 Suraj Shankar , Sriram Ramaswamy , M. Cristina Marchetti , Mark J. Bowick

We describe the flows and morphological dynamics of topological defect lines and loops in three-dimensional active nematics and show, using theory and numerical modelling, that they are governed by the local profile of the orientational…

Soft Condensed Matter · Physics 2020-03-13 Jack Binysh , Žiga Kos , Simon Čopar , Miha Ravnik , Gareth P. Alexander

Collectively moving cellular systems often contain a proportion of dead cells or non-motile genotypes. When mixed, nematically aligning motile and non-motile agents are known to segregate spontaneously. However, the role that topological…

The self-propulsion of +1/2 topological defects is a hallmark of active nematic fluids, where the defects are advected by the flow field they themselves generate. In this paper we propose a minimal model for defect self-propulsion in a…

Soft Condensed Matter · Physics 2025-08-08 Fridtjof Brauns , Myles O'Leary , Arthur Hernandez , Mark J. Bowick , M. Cristina Marchetti

Topological defects in active liquid crystals can be confined by introducing gradients of activity. Here, we examine the dynamical behavior of two defects confined by a sharp gradient of activity that separates an active circular region and…

Soft Condensed Matter · Physics 2021-06-16 Ali Mozaffari , Rui Zhang , Noe Atzin , Juan J. de Pablo

We characterise the particlelike kinematics of charge-carrying topological defects in nematic media via a geometric field theory. This differs from the theory of electromagnetism, with which it is often compared, due to the absence of…

Soft Condensed Matter · Physics 2026-05-22 Joseph Pollard , Richard G. Morris

A nematic liquid crystal confined to the surface of a sphere exhibits topological defects of total charge $+2$ due to the topological constraint. In equilibrium, the nematic field forms four $+1/2$ defects, located at the corners of a…

Soft Condensed Matter · Physics 2020-07-22 Yi-Heng Zhang , Markus Deserno , Zhan-Chun Tu

Defect dynamics in a thin active nematic layer is studied by asymptotic matching of solutions in the defect core and the far field. The analysis is facilitated by the correspondence between the 2D nematic and complex scalar field models.…

Soft Condensed Matter · Physics 2015-06-16 L. M. Pismen
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