Exploring the Formation of Initial Disclination Loops of Active Nematics through Particle-Based Simulations

The dynamics of active nematics are dominated by the spontaneous creation and annihilation of defects, a phenomenon which does not occur in passive equilibrium systems. While the loops and networks formed by 3D disclinations in active nematics has recently become a research focus, the underlying mechanics governing the emergence of initial disclinations from an ordered background remains unclear. In this work, we propose a simple model for the formation of an initial disclination loop within the framework inspired by biaxial nematics. We analyze this model with large-scale particle-based simulations of 3D dry active nematic filaments, performed over a range of activity and filament bending modulus values. Surprisingly, we find that the topological properties of initial loops (the prevalence of wedge-twist or pure-twist type configurations) are highly sensitive to microscopic simulation parameters. By analyzing simulation trajectories, we attribute this correlation to the interplay of two competing time scales: the undulation of directors and the nucleation of defects.