Crossing $w=-1$ by a single scalar field coupling with matter and the   observational constraints
  Motivated by Yang-Mills dark energy model, we propose a new model by introducing a logarithmic correction. we find that this model can avoid the coincidence problem naturally and gives an equation of state $w$ smoothly crossing -1 if an interaction between dark energy and dark matter exists. It has a stable tracker solution as well. To confront with observations based on the combined data of SNIa, BAO, CMB and Hubble parameter, we obtain the best fit values of the parameters with $1\sigma, 2\sigma, 3\sigma$ errors for the noncoupled model: $\Omega_m=0.276\pm0.008^{+0.016+0.024}_{-0.015-0.022}$, $h=0.699\pm0.003\pm0.006\pm0.008$, and for the coupled model with a decaying rate $\gamma=0.2$: $\Omega_m=0.291\pm0.004^{+0.008+0.012}_{-0.007-0.011}$, $h=0.701\pm0.002\pm0.005\pm0.007$. In particular, it is found that the non-coupled model has a dynamic evolution almost undistinguishable to $\Lambda$CDM at the late-time Universe. 
Ming-Lei Tong, Yang Zhang, Zheng-Wen Fu
astro-ph.CO gr-qc hep-ph hep-th