Phantom Thermodynamics Revisited
  Although generalized Chaplygin phantom models do not show any big rip singularities, we investigated k-essence models together with noncanonical kinetic energy for which there might be a big rip future singularity in the phantom region. We present our results by finely tuning the parameter ($\beta$) which is closely related to the canonical kinetic term in $k$-essence formalism. The scale factor $a(t)$ could be negative and decreasing within a specific range of $\beta$ during the initial evolutional period. There will be no singularity for the scale factor for all times once $\beta$ is carefully selected. 
A. Kwang-Hua Chu