Single mechanism for generating large-scale structure and providing dark missing matter

We consider a boson field with a phase transition driven by a cosmologically small quartic self-coupling. While its short-wavelength components are stabilized, its very-long-wavelength components start a ``slow-rolling'' phase transition as soon as they come within their horizon. The Universe becomes filled with a critical density of ``soft-boson'' particles with a Compton wavelength of tens of kiloparsecs. Large-scale structure with present size tens of megaparsecs is inescapably formed by the wave-packet dynamics of such soft bosons. Baryons are gravitationally coupled to this structure. The Heisenberg uncertainty principle prevents soft bosons from falling into clusters of galaxies.