A late-time transition in the equation of state versus Lambda-CDM
  We study a model of the dark energy which exhibits a rapid change in its equation of state w(z), such as occurs in vacuum metamorphosis. We compare the model predictions with CMB, large scale structure and supernova data and show that a late-time transition is marginally preferred over standard Lambda-CDM. 
B.A. Bassett, M. Kunz, J. Silk and C. Ungarelli