Spin-thermal shear coupling in a relativistic fluid

We show that spin polarization of a fermion in a relativistic fluid at local thermodynamic equilibrium can be generated by the symmetric derivative of the four-temperature vector, defined as thermal shear. As a consequence, besides vorticity, acceleration and temperature gradient, also the shear tensor contributes to the polarization of particles in a fluid. This contribution to the spin polarization vector, which is entirely non-dissipative, adds to the well known term proportional to thermal vorticity and may thus have important consequences for the solution of the local polarization puzzles observed in relativistic heavy ion collisions. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

It is shown that the shear tensor in a relativistic fluid contributes to the spin polarization of particles in addition to vorticity, acceleration, and temperature gradient. This non-dissipative contribution to the spin polarization vector may have important consequences for solving local polarization puzzles seen in relativistic heavy ion collisions.