Spontaneous oscillations and geometric cutoff in confined bacterial swarms
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arXiv
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| Format: | Preprint |
| Published: |
2026
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| _version_ | 1866915894720987136 |
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| author | Miao, Bing Tang, Lei-Han |
| author_facet | Miao, Bing Tang, Lei-Han |
| contents | Self-organized dynamic patterns in dense active matter are striking manifestations of non-equilibrium physics. A prominent example is the macroscopic elliptical motion observed in quasi-2D bacterial suspensions, which has lacked a physical explanation. Here, we examine a minimal linear response framework coupling bacterial swimming dynamics with fluid flow, treating long-range hydrodynamic interactions as a macroscopic communication channel. We demonstrate that microscopic swim motion, via Jeffery coupling, manifests as a ``phase-leading'' response to local shear flows. System-wide sustained oscillations, on the other hand, require both a critical bacterial density and strict geometric confinement. By analytically predicting the onset cell density and maximum film thickness, our model achieves excellent quantitative agreement with experiments, establishing a unified physical framework for self-organized periodic motion of elongated body in active fluids. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_26025 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Spontaneous oscillations and geometric cutoff in confined bacterial swarms Miao, Bing Tang, Lei-Han Soft Condensed Matter Biological Physics Fluid Dynamics Self-organized dynamic patterns in dense active matter are striking manifestations of non-equilibrium physics. A prominent example is the macroscopic elliptical motion observed in quasi-2D bacterial suspensions, which has lacked a physical explanation. Here, we examine a minimal linear response framework coupling bacterial swimming dynamics with fluid flow, treating long-range hydrodynamic interactions as a macroscopic communication channel. We demonstrate that microscopic swim motion, via Jeffery coupling, manifests as a ``phase-leading'' response to local shear flows. System-wide sustained oscillations, on the other hand, require both a critical bacterial density and strict geometric confinement. By analytically predicting the onset cell density and maximum film thickness, our model achieves excellent quantitative agreement with experiments, establishing a unified physical framework for self-organized periodic motion of elongated body in active fluids. |
| title | Spontaneous oscillations and geometric cutoff in confined bacterial swarms |
| topic | Soft Condensed Matter Biological Physics Fluid Dynamics |
| url | https://arxiv.org/abs/2603.26025 |