Speaker
Description
Mostly based on: F. Becattini, W. Florkowski, Phys. Lett. B 789 (2019) 419-425
The search for and the recent evidence of polarization in relativistic heavy
ion collisions has raised fundamental questions about the most general theoretical
description of a relativistic polarizable neutral medium and especially about
the role of the spin tensor in relativistic hydrodynamics. The so-called pseudo-
gauge invariance under transformations of the stress-energy and spin tensors
prescribes that all final state measurements should be independent of the particular
tensor operators chosen to describe the relativistic fluid. In this talk, I will
review the subject and discuss the fundamental definitions of local equilibrium,
spin potential and polarization in a Quantum Field Theory framework. As the local
equilibrium density operator turns out not to be pseudo-gauge invariant, I will
discuss the phenomenological consequences for polarization.
