Ordering and Correlations of Active Nematic Defects in 2D Flat Space

Topological defects are regions in an ordered material where the characteristic order is undefined. These defects are of significant interest in understanding the dynamics of active nematics, which are intrinsically out of equilibrium. One of the aims of our work is to address the orientation of defects in curved geometries. However, in this talk, I will discuss our results in flat space.We first explain how we prepare and image the system and how we identify defects using image analysis techniques. We focus on their orientation calculated directly from the divergence of the nematic tensor order parameter. We then use the defect positions and orientations to define relevant order parameters – polar and nematic order for the +1/2 defects, and a 3-fold bond angle order for the -1/2 defects. These quantities give us insights on the average orientational ordering of our system of defects. We then proceed to look at orientational correlations, and present insights into the configurations adopted by the defects as a function of the inter-defect spacing. Remarkably, we find that the local orientational order persists irrespective of the defect density.