Holographic dark energy model with Hubble horizon as an IR cut-off

Abstract

The main task of this paper is to realize a cosmic observational compatible universe in the framework of holographic dark energy model when the Hubble horizon H is taken as the role of an IR cut-off. When the model parameter c of a time variable cosmological constant (CC) Λ(t) = 3c2H2(t) becomes time or scale dependent, an extra term enters in the effective equation of sate (EoS) of the vacuum energy weffΛ = −c2−dln c2/3dln a. This extra term can make the effective EoS of time variable CC cross the cosmological boundary and be phantom-like at present. For the lack of a first principle and fundamental physics theory to obtain the form c2, we give a simple parameterized form of c2 as an example. Then the model is confronted by the cosmic observations including SN Ia, BAO and CMB shift parameter R. The result shows that the model is consistent with cosmic observations.