Transport Meeting

The measurement of spin polarization in heavy-ion collisions spurred theoretical research in different directions. Among these, spin hydrodynamics advocates for including the spin tensor as an independent degree of freedom in hydrodynamics. However, the definition of the spin tensor is not unique, an ambiguity known as pseudogauge symmetry that hinders the interpretation of spin hydrodynamics. Here, I show that the a rotating NJL model with axial current interactions is equivalent to a theory of spin hydrodynamics with a specific choice of spin tensor. This duality suggests that the underlying QCD dynamics can automatically select the spin tensor for the statistical description of hadrons, solving the pseudogauge ambiguity. The conclusions of this study favor the use of the canonical spin tensor.