Synthetic magnetism for photon fluids
  We develop a theory of artificial gauge fields in photon fluids for the cases of both second-order and third-order optical nonlinearities. This applies to weak excitations in the presence of pump fields carrying orbital angular momentum, and is thus a type of Bogoliubov theory. The resulting artificial gauge fields experienced by the weak excitations are an interesting generalization of previous cases and reflect the PT-symmetry properties of the underlying non-Hermitian Hamiltonian. We illustrate the observable consequences of the resulting synthetic magnetic fields for examples involving both second-order and third-order nonlinearities. 
N. Westerberg, C. Maitland, D. Faccio, K. Wilson, P. \"Ohberg, E. M.   Wright
cond-mat.quant-gas cond-mat.other physics.flu-dyn physics.optics quant-ph