Extended complex scalar field as quintessence
  In this paper, we show the possibility that an extended complex scalar field can be considered as an extended complex quintessence. For this model, we derive the basic equations with a parameter $\eta $ which govern the evolution of the Universe. Our model may contain a complex quintessence model for $\eta =-1$ and a real quitessence model for $\eta =0$. 
Yi-Huan Wei