Did the dark energy always have a large Compton wavelength?

Abstract

Until now all well-studied dark energy models proposed have very large Compton wavelengths, $λ_c > 100 Mpc$ at all time and hence show no clustering on small scales. Evidence against this would disfavour both $Λ$CDM and quintessence. We show however, that large $λ_c$ is actually favoured by current CMB, LSS and SN1a data by comparing quintessence with a condensate scenario with the same background dynamics. The condensate scenario has a very small $λ_c$ before making a transition to negative pressure and large $λ_c$ and therefore exhibits a rich CMB phenomenology which roughly interpolates between $Λ$CDM and flat CDM models.