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Short-time dynamics of topological defects in Bacillus subtilis swarms

Ascertain the dynamical regime of topological defect motion at short time scales in Bacillus subtilis swarms, determining whether the trajectories are ballistic, superdiffusive, or diffusive and quantifying the corresponding scaling behavior.

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Background

The authors analyze defect trajectories and find that +1/2 defects appear superdiffusive (possibly ballistic) over 0.3–1 s, while −1/2 defects appear diffusive; at longer times, rotational diffusion is observed. However, short-time behavior could not be resolved due to detection noise.

Clarifying the short-time dynamics would refine the comparison with active nematic theory, which predicts superdiffusive behavior for both defect types at sufficiently short times.

References

On shorter time scales, the nature of the dynamics is unclear due to the inherent noise in identifying defects.

— Topological defects in multi-layered swarming bacteria (2401.05560 - Yashunsky et al., 10 Jan 2024) in Results, Single-layer analysis; paragraph on defect trajectories near Fig. 4