A New Class of Parametrization for Dark Energy without Divergence
  In this paper, we propose a new class of parametrization of the equation of state of dark energy. In contrast with the famous CPL parametrization, these new parametrization of the equation of state does not divergent during the evolution of the Universe even in the future. Also, we perform a observational constraint on two simplest dark energy models belonging to this new class of parametrization, by using the Markov Chain Monte Carlo (MCMC) method and the combined latest observational data from the type Ia supernova compilations including Union2(557), cosmic microwave background, and baryon acoustic oscillation. 
Chao-Jun Feng, Xian-Yong Shen, Ping Li, Xin-Zhou Li
astro-ph.CO hep-th