This seminar is a part of the activities of Center for Strings, Gravitation and Cosmology of IIT Madras
After an introduction of the relevant concepts, we are going to discuss recent progress in the construction of relativistic spin hydrodynamics. Using the second law of local thermodynamics and the first-order Palatini formalism, we will formulate relativistic spin hydrodynamics for quantum field theories with Dirac fermions, such as QED and QCD, in a torsionful curved background. Spin density is assumed to relax much slower than other non-hydrodynamic modes in some regimes of experiments. We are going to work in such a regime, and treat spin density as an independent degree of freedom in an extended hydrodynamic description. A new transport coefficient controls the spin relaxation: the rotational viscosity. Lastly, we will outline how holography can significantly contribute to the construction and testing of spin hydrodynamics.