Fate of spin polarization in a relativistic fluid; An Entropy-current analysis

服部 恒一*; 本郷 優*; Huang, X.-G.*; 松尾 衛; 田屋 英俊*

Physics Letters B, 795, p.100 - 106, 2019/08

https://doi.org/10.1016/j.physletb.2019.05.040

We derive relativistic hydrodynamic equations with a dynamical spin degree of freedom on the basis of an entropy-current analysis. The first and second laws of local thermodynamics constrain possible structures of the constitutive relations including a spin current and the antisymmetric part of the (canonical) energy-momentum tensor. Solving the obtained hydrodynamic equations within the linear-mode analysis, we find spin-diffusion modes, indicating that spin density is damped out after a characteristic time scale controlled by transport coefficients introduced in the antisymmetric part of the energy-momentum tensor in the entropy-current analysis. This is a consequence of mutual convertibility between spin and orbital angular momentum.