Revisiting the holographic dark energy in a non-flat universe: alternative model and cosmological parameter constraints

摘要

We propose an alternative model for the holographic dark energy in a non-flat universe. This new model differs from the previous one in that the IR length cutoff (L) is taken to be exactly the event horizon size in a non-flat universe, which is more natural and theoretically/conceptually concordant with the model of holographic dark energy in a flat universe. We constrain the model using the recent observational data including the type Ia supernova data from SNLS3, the baryon acoustic oscillation data from 6dF, SDSS-DR7, BOSS-DR11, and WiggleZ, the cosmic microwave background data from Planck, and the Hubble constant measurement from HST. In particular, since some previous studies have shown that the color–luminosity parameter (eta ) of supernovae is likely to vary during the cosmic evolution, we also consider such a case that (eta ) in SNLS3 is time-varying in our data fitting. Compared to the constant (eta ) case, the time-varying (eta ) case reduces the value of (chi ^2) by about 35 and results in that (eta ) deviates from a constant at about 5(sigma ) level, well consistent with the previous studies. For the parameter (c) of the holographic dark energy, the constant (eta ) fit gives (c=0.65pm 0.05) and the time-varying (eta ) fit yields (c=0.72pm 0.06). In addition, an open universe is favored (at about 2(sigma )) for the model by the current data.