Transition of the dark energy equation of state in an interacting   holographic dark energy model
  A model of holographic dark energy with an interaction with matter fields has been investigated. Choosing the future event horizon as an IR cutoff, we have shown that the ratio of energy densities can vary with time. With the interaction between the two different constituents of the universe, we observed the evolution of the universe, from early deceleration to late time acceleration. In addition, we have found that such an interacting dark energy model can accommodate a transition of the dark energy from a normal state where $w_D>-1$ to $w_D<-1$ phantom regimes. Implications of interacting dark energy model for the observation of dark energy transition has been discussed. 
Bin Wang, Yungui Gong and Elcio Abdalla