@article{14377,
  abstract     = {Coherent flows of self-propelled particles are characterized by vortices and jets that sustain chaotic flows, referred to as active turbulence. Here, we reveal a crossover between defect-free active turbulence and active turbulence laden with topological defects. Interestingly, we show that concurrent to the crossover from defect-free to defect-laden active turbulence is the restoration of the previously broken SO(2) symmetry signaled by the fast decay of the two-point correlations. By stability analyses of the topological charge density field, we provide theoretical insights on the criterion for the crossover to the defect-laden active turbulent state. Despite the distinct symmetry features between these two active turbulence regimes, the flow fluctuations exhibit universal statistical scaling behaviors at large scales, while the spectrum of polarity fluctuations decays exponentially at small length scales compared to the active energy injection length. These findings reveal a dynamical crossover between distinct spatiotemporal organization patterns in polar active matter.},
  author       = {Andersen, Benjamin H. and Renaud, Julian B and Rønning, Jonas and Angheluta, Luiza and Doostmohammadi, Amin},
  issn         = {2469-990X},
  journal      = {Physical Review Fluids},
  keywords     = {Fluid Flow and Transfer Processes, Modeling and Simulation, Computational Mechanics},
  number       = {6},
  publisher    = {American Physical Society},
  title        = {{Symmetry-restoring crossover from defect-free to defect-laden turbulence in polar active matter}},
  doi          = {10.1103/physrevfluids.8.063101},
  volume       = {8},
  year         = {2023},
}

@article{14087,
  abstract     = {Polar active matter of self-propelled particles sustain spontaneous flows through the full-integer topological defects. We study theoretically the incompressible flow profiles around ±1 defects induced by polar and dipolar active forces. We show that dipolar forces induce vortical flows around the +1 defect, while the flow around the −1 defect has an 8-fold rotational symmetry. The vortical flow changes its chirality near the +1 defect core in the absence of the friction with a substrate. We show analytically that the flow induced by polar active forces is vortical near the +1 defect and is 4-fold symmetric near the −1 defect, while it becomes uniform in the far-field. For a pair of oppositely charged defects, this polar flow contributes to a mutual interaction force that depends only on the orientation of the defect pair relative to the background polarization, and that enhances defect pair annihilation. This is in contradiction with the effect of dipolar active forces which decay inversely proportional with the defect separation distance. As such, our analyses reveals a long-ranged mechanism for the pairwise interaction between topological defects in polar active matter.},
  author       = {Rønning, Jonas and Renaud, Julian B and Doostmohammadi, Amin and Angheluta, Luiza},
  issn         = {1744-6848},
  journal      = {Soft Matter},
  pages        = {7513--7527},
  publisher    = {Royal Society of Chemistry},
  title        = {{Spontaneous flows and dynamics of full-integer topological defects in polar active matter}},
  doi          = {10.1039/d3sm00316g},
  volume       = {39},
  year         = {2023},
}