Critical state of phantom universe
  The late-time evolution behavior of the autonomous system in the SO(1,1) dark energy model with power-law potential is studied. Big Rip may be a critical point of the autonomous system. This means that such a Big Rip may be considered as the middle state between the expanding and contracting phases of phantom universe. This result is also valid for some special interactions between matter and dark energy. 
Yi-Huan Wei