  Topological spin transport of electromagnetic waves (photons) in stationary
smoothly inhomogeneous isotropic medium is studied. By diagonalizing photon
kinetic energy in Maxwell equations we derive the non-Abelian pure gauge
potential in the momentum space, which in adiabatic approximation for
transverse waves takes the form of two Abelian U(1) potentials corresponding to
magnetic monopole-type fields. These fields act on circularly polarized waves
resulting in the topological spin transport of photons. We deduce general
semiclassical (geometrical optics) ray equations that take into account a
Lorentz-type force of the magnetic-monopole-like gauge field. Detailed analysis
of rays in 3D medium with 2D periodic inhomogeneity is presented. It is shown
that rays located initially in the inhomogeneity plane experience topological
deflections or splitting that move them out from this plane. The dependence of
the rays' deflection on the parameters of the medium and on the direction of
propagation is studied.
