Title: The Physics of Living Fluid Turbulence

Speaker: Dr. Siddhartha Mukherjee, International Centre for Theoretical Sciences, Bangalore

Abstract: Living fluids, a complex organization of matter driven at the scale of its constituent agents, exhibit confounding states like "active turbulence". Analogies with high Reynolds number, inertial (Kolmogorovean) turbulence, however, have not survived beyond the qualitative. Using a continuum hydrodynamic model for dense bacterial suspensions, we investigate features distinguishing active from inertial turbulence. We find a flow transition to universality beyond a critical activity, which is accompanied by intermittency and maximal chaos. Interestingly, this asymptotic flow state manifests superdiffusion via Lévy walks, and consequently other Lagrangian anomalies, which we trace back to oscillatory streaks emerging in the Eulerian flow field - features that set living flows distinctly apart from inertial turbulence limited to classical diffusion. All of this makes the phenomenology of living matter rich and riddled with surprising nuances, which at times bridge the analogy with inertial turbulence, and at others break them. Broad-brushed parallels, therefore, obfuscate what may be biologically relevant strategies for survival and growth.