Interference of Dark Matter Solitons and Galactic Offsets
  By performing numerical simulations, we discuss the collisional dynamics of
stable solitary waves in the Schrodinger-Poisson equation. In the framework of
a model in which part or all of dark matter is a Bose-Einstein condensate of
ultralight axions, we show that these dynamics can naturally account for the
relative displacement between dark and ordinary matter in the galactic cluster
Abell 3827, whose recent observation is the first empirical evidence of dark
matter interactions beyond gravity. The essential assumption is the existence
of solitonic galactic cores in the kiloparsec scale. For this reason, we
present simulations with a benchmark value of the axion mass $m_a = 2 \times
10^{-24}$ eV, which is somewhat lower than the one preferred for cosmological
structure formation if the field is all of dark matter ($m_a \approx
10^{-22}$eV). We argue that future observations might bear out or falsify this
coherent wave interpretation of dark matter offsets.
