Speaker
Description
We compare thermodynamic and kinetic approaches, that have been recently
used to study relations between the spin polarization and fluid
vorticity in systems consisting of spin-one-half particles. The
thermodynamic approach refers to general properties of global thermal
equilibrium with a rigid-like rotation and demonstrates that the
spin-polarization and thermal-vorticity tensors are equal. On the other
hand, the kinetic approach uses the concept of the Wigner function and
its semiclassical expansion. In most of the works done so far, the
Wigner functions satisfy kinetic equations with a vanishing collision
term. We show that this assumption restricts significantly applicability
of such frameworks and, in contrast to many claims found in the
literature, does not allow for drawing any conclusions regarding the
relation between the thermal-vorticity and spin-polarization tensors,
except for the fact that the two should be constant in global
equilibrium. We further show how the kinetic-theory equations including
spin degrees of freedom can be used to formulate a hydrodynamic
framework for particles with spin.
