Coincidence Problem in YM Field Dark Energy Model
  The coincidence problem is studied in the effective Yang-Mills condensate dark energy model. As the effective YM Lagrangian is completely determined by quantum field theory, there is no adjustable parameter in this model except the energy scale, and the cosmic evolution only depends on the initial conditions. For generic initial conditions with the YM condensate subdominant to the radiation and matter, the model always has a tracking solution, the Universe transits from matter-dominated into the dark energy dominated stage only recently $z\sim 0. 3$, and evolve to the present state with $\Omega_{y}\sim 0.73$ and $\Omega_m\sim 0.27$. 
Wen Zhao, Yang Zhang