SO (1, 1) dark energy model and the universe transition

We suggest a scalar model of dark energy with the SO (1, 1) symmetry. The model may be reformulated in terms of a real scalar field and the scale factor a so that the Lagrangian may be decomposed as that of the real quintessence model plus the negative coupling energy term of to a. The existence of the coupling term Lᶜ leads to a wider range of w_ and overcomes the problem of negative kinetic energy in the phantom universe model. We propose a power-law expansion model of univese with time-dependent power, which can describe the phantom universe and the universe transition from ordinary acceleration to super acceleration.