Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X53: Geometry and Topology of Active MatterInvited
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Sponsoring Units: GSOFT Chair: Vincenzo Vitelli, Univ of Chicago Room: BCEC 253C |
Friday, March 8, 2019 8:00AM - 8:36AM |
X53.00001: Curvature-driven topological protection Invited Speaker: Mark Bowick Active systems on curved geometries are ubiquitous in the living world. Ordered polar flocks in the presence of spatial curvature are forced to be inhomogeneous and must also exhibit topological defects, even in the steady state, when the curved manifold is topologically non-trivial. I will discuss how dynamical symmetry breaking via spontaneous flow (flocking), together with spatial curvature, are the only ingredients necessary to produce long-wavelength symmetry-protected gapped sound modes. The steady state profile of an active polar flock on a two-sphere and a catenoid will be presented. The topologically-protected sound modes are localized to special geodesics on the surface (the equator or the neck respectively). These modes are the analogue of edge states in electronic quantum Hall systems and provide unidirectional channels for information transport in the flock, robust against disorder and backscattering. |
Friday, March 8, 2019 8:36AM - 9:12AM |
X53.00002: Defect ordering and geometrical control in passive and active nematic liquid crystals Invited Speaker: Luca Giomi In this talk, I will discuss some recent theoretical and experimental work on active nematic liquid crystals confined on two-dimensional curved interfaces and highlight how the geometrical and topological structure of the environment can substantially affect collective motion in active materials, leading to spectacular life-like functionalities. |
Friday, March 8, 2019 9:12AM - 9:48AM |
X53.00003: Odd Elasticity in Active Metamaterials Invited Speaker: Colin Scheibner The theory of elasticity provides a foundation for describing the mechanics of deformations of continuous media. However, elastic theories of active matter must confront a fundamental challenge: the starting point of elasticity, the elastic energy, is not well defined due to microscopic activity. We introduce Odd Elasticity as a generalized theory of continuum mechanics that breaks key symmetries of the elastic (stiffness) tensor otherwise required by conservation of energy. We show that odd elasticity describes solids in which activity depends on the deformation of microscopic bonds. As a minimal model that produces odd elasticity upon coarse graining, we consider active metamaterials in which internal torques are actuated in response to compression or extension of the beams. Our odd-elastic theory, corroborated by simulations, sheds light on a rich phenomenology, including activity-induced auxetic behavior, active elastic waves and instabilities. Our work revisits the foundations of continuum mechanics and provides a blueprint for the design of active elastic engines, which utilize a strain cycle to convert microscopic activity into useful mechanical work. |
Friday, March 8, 2019 9:48AM - 10:24AM |
X53.00004: The odd free surface flows of a colloidal chiral fluid Invited Speaker: William T. M. Irvine TBD |
Friday, March 8, 2019 10:24AM - 11:00AM |
X53.00005: Topological defects in cell layers Invited Speaker: Julia Yeomans TBD |
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