MSc defense by Lasse F. Bonn

Title: Fluctuation-induced motility of topological defects

Abstract: Topological defects are increasingly being discovered in biological systems and are being shown to play a functional role in e.g. tissue homeostasis or limb origination due to induced flow and stress patterns. In this work, we show that for a wet passive nematic, fluctuations in orientation or velocity, along with elastic effects can result in defects showing self propulsion and stress patterns similar to those in active nematics. Using  continuum simulations of fluctuating nematohydrodynamics, we can reproduce the self-propelled defect chaos phase, characteristic of active nematics. Both hydrodynamic and orientational fluctuations reproduce this phase along with the flow patterns and the functional stress patterns. We show the possibility of both extensile and contractile defect motion arising from fluctuations and the essential role that elastic effects play in establishing this new phenomenon.