LATE-TIME PHASE-TRANSITION AND THE GALACTIC HALO AS A BOSE-LIQUID

We consider the ultralight pseudo Nambu-Goldstone boson appearing in t he late-time cosmological phase transition theories as a major dark ma tter candidate. Since it is almost massless, its nature is more waveli ke than particlelike. We study quantum mechanically how they form a ga lactic halo. Three predictions are made: (i) the mass profile rho simi lar to r(-1.6); (ii) there are ripplelike fine structures in the rotat ion curve; (iii) the rotation velocity multiplied by the ripple's wave length is galaxy independent.