Nonlinear hydrodynamics of axion dark matter: Relative velocity effects and quantum forces
Nonlinear hydrodynamics of axion dark matter: Relative velocity effects and quantum forces
The nonlinear hydrodynamic equations for axion/scalar field dark matter (DM) in the nonrelativistic Madelung-Shcr\"odinger form are derived in a simple manner, including the effects of universal expansion and Hubble drag. The hydrodynamic equations are used to investigate the relative velocity between axion DM and baryons, and the moving-background perturbation theory …