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.

中文翻译：

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相对论流体中的自旋-热剪切耦合

我们表明，在局部热力学平衡的相对论流体中费米子的自旋极化可以通过四温度矢量的对称导数产生，定义为热剪切。因此，除了涡度、加速度和温度梯度之外，剪切张量也有助于流体中粒子的极化。这种对完全非耗散的自旋极化矢量的贡献增加了与热涡度成正比的众所周知的术语，因此可能对解决在相对论重离子碰撞中观察到的局部极化难题具有重要意义。