Unified Dark Matter, Dark Energy and baryogenesis via a cosmological wetting transition

In a recent publication [1], a cosmological scenario featuring a scalar field, phi, that is a source for Dark Matter and Dark Energy has been proposed. In this paper, a concrete realization of that scenario is presented. As in many models of scalar-field driven Dark Energy, the effective Lagrangian of the field phi contains a potential proportional to e(-phi/integral) This potential is modulated in such a way that, in the absence of other matter fields, it has a local minimum at a small value of phi. Fluctuations of phi around this minimum give rise to a gas of dark-matter particles. The field phi is coupled to another scalar field chi in such a way that the minimum in the effective potential of phi disappears when, after a continuous phase transition accompanied by spontaneous symmetry breaking, chi develops a non-vanishing expectation value. This triggers slow growth of a homogeneous component of phi accompanied by the emergence of Dark Energy, a phenomenon analogous to the wetting transition in statistical mechanics. Inside regions of the Universe where the pressure is small and the energy density is large enough to stall expansion, in particular around galaxies and galaxy clusters, the phase transition in the state of chi does not take place, and a gas of cold dark-matter particles persists. The evolution of phi at very early times may tune the rate of baryogenesis.