Emergence of Local Ordering and Mesoscale Giant Number Fluctuations in Active Turbulence
Phys. Rev. Lett. 136, 108301 – Published 11 March, 2026
DOI: https://doi.org/10.1103/ylbh-8v74
Abstract
We study spatiotemporal chaos in two-dimensional dense active suspensions using a generalized hydrodynamic model. Increasing activity induces a structural transition marked by the formation of intense vortices and giant number fluctuations at the mesoscale. The flow self-organizes into locally polar-ordered regions coexisting with chaotic domains, producing a bimodal velocity distribution and enhanced correlations. This mixed-state morphology underlies the universal statistical behavior observed beyond a critical activity threshold. Reducing the instability timescale yields similar transitions, showing that both activity and instability act as control parameters for pattern formation. An energy-based order parameter derived from the system’s budget quantifies and unifies these structural transitions across the phase space of activity and instability timescales.
