Defect line coarsening and refinement in active nematics

Three-dimensional active nematics are based on self-propelled building blocks that exhibit orientational order, characterized by the continuously evolving of topological defects. We focus on the dynamics towards and between dynamic steady state of 3D active nematic turbulence, determined by the coarsening and refinement of topological defect lines and loops. We construct an analytical model of the shrinking and expanding of an isolated active defect loop and then generalize it to the coarsening and refinement dynamics of the 3D active defect network. Our work provides analytic insight into the dynamics of 3D active nematic systems, from the perspective of the emergence of topological defects triggered by changes in the main material parameters, such as activity or even nematic elasticity and viscosity.