Shear induced polarization: collisional contributions

It has been realized that thermal shear plays a similar role as vorticity in polarizing spin of particles heavy ion collisions. We point out fundamental difference it leads to particle redistribution the medium. The gives rise an additional contribution polarization through self-energy, which is parametrically same order one considered so far literature. self-energy general gauge dependent. introduce double links stretching along Schwinger-Keldysh contour restore invariance. also generalize straight path adapt contour. find another associated with link, order. illustrate two contributions massive probe fermion massless QED plasma shear. A modest suppression found from combined when momentum much greater than temperature.