On tachyon and sub-quantum phantom cosmologies
  This paper deals with dark and phantom energy in the tachyon and sub-quantum models for dark energy. We obtain that the simplest condition for such a regime to occur in these scenarios is that the scalar field be Wick rotated to imaginary values which correspond to an axionic field classically. By introducing analytical expressions for the scale factor or the Hubble parameter that satisfy all constraint equations of the used models we show that such models describe universes which develop a big rip singularity in the finite future. 
Pedro F. Gonzalez-Diaz (IMAFF, CSIC, Madrid)