Observational Constraints on Purely Kinetic k-Essence Dark Energy Models

We consider constraints on purely kinetic k-essence models from the latest observational data (including 182 gold SNIa data, the shift parameter, and the acoustic scale). We find the best-fit values of the parameters are Ω_m=0.37±m0.01 and k₀=0.064±0.013 at 68.3% confidence level. The phase transition from deceleration to acceleration is found to occur at redshift z_q=0~0.48-0.52 in 68.3% confidence level limits. By applying model-comparison statistics (F-test, AIC_c, and BIC), we find that the purely kinetic k-essence scenario is favored over the ΛCDM model by the combined data. These results are also confirmed by combined data 307 SNIa+R+l_a.