Kinetic theory of topological defects in active nematics

Active nematics are fluids of elongated active agents that exhibit self-sustained flows
and liquid crystalline order. Realizations include suspensions of cytoskeletal filaments
and motor proteins, biological tissue, and vibrated layers of granular rods. At high
activity, active nematics exhibit spatio-temporal chaotic, turbulent-like flows with
proliferation of topological defects. In this talk I will show that, focusing on the defects as
the relevant quasiparticles driving the non-equilibrium dynamics, we can formulate a
kinetic theory of the active defect gas and describe the onset of active turbulence as
activity-driven defect unbinding. By coarse-graining the kinetic theory, we obtain a
hydrodynamic description of the active defect gas.