A generalized Theory of Diffusion based on Kinetic Theory

Understand

We propose to use spin hydrodynamics, a two-fluid model of spin propagation, as a generalization of the diffusion equation.

• We show that in the dense limit spin hydrodynamics reduces to Fick's law and the diffusion equation.
• In the opposite limit spin hydrodynamics is equivalent to a collisionless Boltzmann treatment of spin propagation.
• Spin hydrodynamics avoids unphysical effects that arise when the diffusion equation is used to describe to a strongly interacting gas with a dilute corona.