Brief History of Ultra-light Scalar Dark Matter Models
  This is a review on the brief history of the scalar field dark matter model
also known as fuzzy dark matter, BEC dark matter, wave dark matter, or
ultra-light axion.
  In this model ultra-light scalar dark matter particles with mass $m =
O(10^{-22})eV$ condense in a single Bose-Einstein condensate state and behave
collectively like a classical wave. Galactic dark matter halos can be described
as a self-gravitating coherent scalar field configuration called boson stars.
  At the scale larger than galaxies the dark matter acts like cold dark matter,
while below the scale quantum pressure from the uncertainty principle
suppresses the smaller structure formation so that it can resolve the small
scale crisis of the conventional cold dark matter model.
