The Fluid Manifesto: Topological sigma models and dissipative hydrodynamics

I will describe how to arrive at an effective action for dissipative hydrodynamics starting from the microscopic Schwinger-Keldysh construction. The essential ingredients will the doubling of degrees of freedom, an emergent abelian symmetry that is associated with entropy, and a BRST supersymmetry that ensures fluctuation-dissipation relation. I will show how these elements combine to lead to a non-linear viscous fluid effective action and outline some interesting applications of this line of thought.