  We consider the ultra light pseudo Nambu-Goldstone boson appearing in the
late time cosmological phase transition theories as a dark matter candidate.
Since it is almost massless, its nature is more wave like than particle like.
Hence we apply quantum mechanics to study how they form the galactic halos.
Three predictions are made; (1)the mass profile $\rho\sim r^{-1.6}$, (2)there
are ripple-like fine structures in rotation curve, (3) the rotation velocity
times ripple's wave length is largely galaxy independent. We compare the
rotation curves predicted by our theory with the data observed.
