Condensate cosmology: Dark energy from dark matter

Imagine a scenario in which the dark energy forms via the condensation of dark matter at some low redshift. The Compton wavelength therefore changes from small to very large at the transition, unlike quintessence or metamorphosis. We study cosmic microwave background (CMB), large scale structure, supernova and radio galaxy constraints on condensation by performing a four parameter likelihood analysis over the Hubble constant and the three parameters associated with Q, the condensate field: ${\Omega }_Q,$ $w_f$ and $z_t$ (energy density and equation of state today, and redshift of transition). Condensation roughly interpolates between $\Lambda \mathrm{CDM}$ (for large $z_t)$ and SCDM (low $z_t)$ and provides a slightly better fit to the data than $\Lambda \mathrm{CDM}.$ We confirm that there is no degeneracy in the CMB between H and $z_t$ and discuss the implications of late-time transitions for the Lyman-$\alpha$ forest. Finally we discuss the nonlinear phase of both condensation and metamorphosis, which is much more interesting than in standard quintessence models.