Defect Unbinding in Active Nematic Tori

Presented at the Workshop on Topological Protection in Messy Matter on May 15, 2018 at 9:00 a.m.-9:40 a.m. in the Marcus Nanotechnology Building, Rooms 1116-1118, Georgia Tech.Chairs: Massimo Ruzzene and Vincenzo VitelliAlberto Fernandez-Nieves is with the Georgia Institute of Technology, School of Physics.Runtime: 48:42 minutesWe will discuss our recent results with active nematics on toroidal surfaces and show how, despite the intrinsic activity and out-of-equilibrium character of our system, we still observe remnants of the expected curvature-induced defect unbinding predicted for nematics in their ground state. In our experiments, however, the number of defects is far larger than what one would expect for conventional nematics. In addition, these defects move throughout the toroidal surface and explore "phase space", bringing about interesting analogies with what we could call the high-temperature limit of a nematic liquid crystal. We unravel the role of activity by comparing our results to numerical simulations. Overall, our results illustrate the interplay between order, topological constraints, local geometry and activity