The global attractor of the Toner-Tu-Swift-Hohenberg equations of active turbulence and its properties

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Main Authors: Boutros, Daniel W., Kiran, Kolluru Venkata, Gibbon, John D., Pandit, Rahul
Format: Preprint
Published: 2026
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author Boutros, Daniel W.
Kiran, Kolluru Venkata
Gibbon, John D.
Pandit, Rahul
author_facet Boutros, Daniel W.
Kiran, Kolluru Venkata
Gibbon, John D.
Pandit, Rahul
contents The Toner-Tu-Swift-Hohenberg (TTSH) equations are one of the basic equations that are used to model turbulent behaviour in active matter, specifically the swarming of bacteria in suspension. They combine features of the incompressible Navier-Stokes, the Toner-Tu and Swift-Hohenberg equations, together with the important properties that they are linearly driven, and that the Laplacian diffusion is taken to be negative in combination with hyper-dissipation. We prove that the TTSH equations possess a finite-dimensional compact global attractor on the periodic domain $\mathbb{T}^d$ ($d=2,3$) and we establish explicit estimates for its Lyapunov dimension which agree with the heuristic prediction based on the Swift-Hohenberg length scale. The predominance of this length scale (as a vortex length scale) has been observed in both numerical and experimental studies of bacterial turbulence, so our methods and results provide a rigorous theoretical foundation for this phenomenon. We also carry out pseudospectral direct numerical simulations of these PDEs in dimension $d=2$ through which we obtain Lyapunov spectra for representative parameter values. We show that our numerical results are consistent with the analytically derived rigorous bounds.
format Preprint
id arxiv_https___arxiv_org_abs_2601_18233
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The global attractor of the Toner-Tu-Swift-Hohenberg equations of active turbulence and its properties
Boutros, Daniel W.
Kiran, Kolluru Venkata
Gibbon, John D.
Pandit, Rahul
Fluid Dynamics
Soft Condensed Matter
Analysis of PDEs
Dynamical Systems
Chaotic Dynamics
The Toner-Tu-Swift-Hohenberg (TTSH) equations are one of the basic equations that are used to model turbulent behaviour in active matter, specifically the swarming of bacteria in suspension. They combine features of the incompressible Navier-Stokes, the Toner-Tu and Swift-Hohenberg equations, together with the important properties that they are linearly driven, and that the Laplacian diffusion is taken to be negative in combination with hyper-dissipation. We prove that the TTSH equations possess a finite-dimensional compact global attractor on the periodic domain $\mathbb{T}^d$ ($d=2,3$) and we establish explicit estimates for its Lyapunov dimension which agree with the heuristic prediction based on the Swift-Hohenberg length scale. The predominance of this length scale (as a vortex length scale) has been observed in both numerical and experimental studies of bacterial turbulence, so our methods and results provide a rigorous theoretical foundation for this phenomenon. We also carry out pseudospectral direct numerical simulations of these PDEs in dimension $d=2$ through which we obtain Lyapunov spectra for representative parameter values. We show that our numerical results are consistent with the analytically derived rigorous bounds.
title The global attractor of the Toner-Tu-Swift-Hohenberg equations of active turbulence and its properties
topic Fluid Dynamics
Soft Condensed Matter
Analysis of PDEs
Dynamical Systems
Chaotic Dynamics
url https://arxiv.org/abs/2601.18233