Axion Phantom Energy
  The existence of phantom energy in a universe which evolves to eventually show a big rip doomsday is a possibility which is not excluded by present observational constraints. In this letter it is argued that the field theory associated with a simple quintessence model is compatible with a field definition which is interpretable in terms of a rank-three axionic tensor field, whenever we consider a perfect-fluid equation of state that corresponds to the phantom energy regime. Explicit expressions for the axionic field and its potential, both in terms of an imaginary scalar field, are derived which show that these quantities both diverge at the big rip, and that the onset of phantom-energy dominance must take place just at present. 
Pedro F. Gonzalez-Diaz (IMAFF, CSIC, Madrid)