Phenomenology of Unified Dark Matter models with fast transition
  A fast transition between a standard matter-like era and a late $\Lambda$CDM-like epoch generated by a single Unified Dark Matter component can explain the observed acceleration of the Universe. UDM models with a fast transition should be clearly distinguishable from $\Lambda$CDM (and alternatives) through observations. Here we focus on a particularly simple model and analyse its viability by studying features of the background model and properties of the adiabatic UDM perturbations. 
Alberto Rozas-Fern\'andez, Marco Bruni and Ruth Lazkoz
astro-ph.CO