Spatiotemporal Chaos and Defect Proliferation in Polar-Apolar Active Mixture

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Hauptverfasser: Mondal, Partha Sarathi, Vicsek, Tamas, Mishra, Shradha
Format: Preprint
Veröffentlicht: 2025
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author Mondal, Partha Sarathi
Vicsek, Tamas
Mishra, Shradha
author_facet Mondal, Partha Sarathi
Vicsek, Tamas
Mishra, Shradha
contents Chaotic transitions in inertial fluids typically proceed through a direct energy cascade from large to small scales. In contrast, active systems, composed of self propelled units, inject energy at microscopic scales and therefore exhibit an inverse cascade, giving rise to distinctly unconventional flow patterns. Here, we investigate an active mixture consisting of both apolar and polar self driven components, a setting expected to display richer behaviours than those found in living liquid crystal (LLC) systems, where the apolar constituent is passive. Using numerical solutions of the corresponding hydrodynamic equations, we uncover a variety of complex dynamical states. Our results reveal a non-monotonic response of the apolar species to changes in the density and activity of the polar component. In an intermediate regime, reminiscent of LLC-induced disorder, the system develops a dynamically disordered phase characterised by high-density, chaotically evolving band-like structures and by the continual creation and annihilation of half integer topological defects. We show that this regime exhibits spatiotemporal chaos, which we quantify through two complementary measures: the spectral properties of density fluctuations and the maximal Lyapunov exponent. Together, these findings broaden the understanding of complex transitions in active matter and suggest potential experimental realisations in bacterial suspensions or synthetic microswimmer assemblies.
format Preprint
id arxiv_https___arxiv_org_abs_2512_20289
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Spatiotemporal Chaos and Defect Proliferation in Polar-Apolar Active Mixture
Mondal, Partha Sarathi
Vicsek, Tamas
Mishra, Shradha
Soft Condensed Matter
Statistical Mechanics
Biological Physics
Computational Physics
Chaotic transitions in inertial fluids typically proceed through a direct energy cascade from large to small scales. In contrast, active systems, composed of self propelled units, inject energy at microscopic scales and therefore exhibit an inverse cascade, giving rise to distinctly unconventional flow patterns. Here, we investigate an active mixture consisting of both apolar and polar self driven components, a setting expected to display richer behaviours than those found in living liquid crystal (LLC) systems, where the apolar constituent is passive. Using numerical solutions of the corresponding hydrodynamic equations, we uncover a variety of complex dynamical states. Our results reveal a non-monotonic response of the apolar species to changes in the density and activity of the polar component. In an intermediate regime, reminiscent of LLC-induced disorder, the system develops a dynamically disordered phase characterised by high-density, chaotically evolving band-like structures and by the continual creation and annihilation of half integer topological defects. We show that this regime exhibits spatiotemporal chaos, which we quantify through two complementary measures: the spectral properties of density fluctuations and the maximal Lyapunov exponent. Together, these findings broaden the understanding of complex transitions in active matter and suggest potential experimental realisations in bacterial suspensions or synthetic microswimmer assemblies.
title Spatiotemporal Chaos and Defect Proliferation in Polar-Apolar Active Mixture
topic Soft Condensed Matter
Statistical Mechanics
Biological Physics
Computational Physics
url https://arxiv.org/abs/2512.20289