Ja n 20 07 Accelerating cosmologies tested by distance measures

We test if the latest Gold set of 182 SNIa or the combined " Platinum " set of 192 SNIa from the ESSENCE and Gold sets, in conjunction with the CMB shift parameter show a preference between the ΛCDM model, three wCDM models, and the DGP model of modified gravity as an explanation for the current accelerating phase of the universe's expansion. We consider flat wCDM models with an equation of state w(a) that is (i) constant with scale factor a, (ii) varies as w 0 + w a (1 − a) for redshifts probed by supernovae but is fixed at −1 at earlier epochs and (iii) varies as w 0 + w a (1 − a) since recombination. We find that all five models explain the data with comparable success.