Ludovic Dumoulin | Searcharxiv

arXiv2026

Active topological strings in renewing nematopolar fluids

Active matter often simultaneously exhibits different kinds of orientational order and, in many cases of biological interest, undergoes continuous material renewal. In renewing nematopolar fluids we find stable topological strings, structures consisting of two nematic point defects connected by a defect line in the polar field. We identify the mechanism underlying string stabilization and unveil how string length is determined. In the presence of active stress, we observe active-string chaos. Our work identifies continuous material renewal as a generic mechanism underlying the stabilization of topological defect structures in systems with mixed order parameters. It could be used for orchestrating living matter during development and other biological processes.

cond-mat.soft↗

arXiv2025

Defect states in compressible active polar fluids with turnover

Biological active matter like the cytoskeleton or tissues are characterized by their ability to transform chemical energy into mechanical stress. In addition, it often exhibits orientational order, which is essential for many cellular and morphogenetic processes. Experimental evidence suggests that defects in the orientational order field play an important role in organizing active stress. However, defects tend to annihilate unless the material is in a chaotic state or hydrodynamic interactions are suppressed. Using a hydrodynamic description of compressible active polar fluids, we show that turnover readily leads to a stabilization of defects. Depending on the turnover rate, topological defects arrange in a multitude of different phases, including lattices, active foams, and vortex glasses. Our work suggests that turnover plays a crucial role for organizing biological active matter.

physics.bio-ph↗