A closer look at the cosmological implications of the ΛHDE model

Abstract

In a previous paper Hu et al. (2015), we proposed a heterotic dark energy model, called ΛHDE, in which dark energy is composed of two components: cosmological constant (CC) and holographic dark energy (HDE). The aim of this work is to give a more comprehensive and systematic investigation on the cosmological implications of the ΛHDE model. Firstly, we make use of the current observations to constrain the ΛHDE model, and compare its cosmology-fit results with the results of the ΛCDM and the HDE model. Then, by combining a qualitative theoretical analysis with a quantitative numerical study, we discuss the impact of considering curvature on the cosmic evolutions of fractional HDE density Ω hde and fractional CC density Ω Λ , as well as on the ultimate cosmic fate. Finally, we explore the effects of adopting different types of observational data. We find that: (1) the current observational data cannot distinguish the ΛHDE model from the ΛCDM and the HDE model; this indicates that DE may contain multiple components. (2) the asymptotic solution of Ω hde and the corresponding cosmic fate in a flat universe can be extended to the case of a non-flat universe; moreover, compared with the case of a flat universe, considering curvature will make HDE closer to a phantom dark energy. (3) compared with JLA dataset, SNLS3 data more favor a phantom type HDE; in contrast, using other types of observational data have no significant impact on the cosmic evolutions of the ΛHDE model.1 The original HDE model have the circular logic problem. In other words, the existence of the future event horizon needs the accelerating expansion, while the dark energy component that cause accelerating expansion is given by the future event horizon. Due to this problem, the original HDE model cannot be derived by the action principle. But in a paper of our group Li & Miao (2012), we have constructed a action, which can derive the energy density form of HDE from the first principle. This means that, although it seems that the original HDE model has the circular logic problem, this problem is not a real problem in the framework of HDE. c 0000 RAS arXiv:1605.04356v2 [astro-ph.CO]

Holographic dark energy

“…A most distinct feature of this table is that all the combinations of observational data mildly favor the case of C < 1, which corresponds to a phantom universe with big rip. Similar results were obtained in [228,229,230,231,232,233]. Moreover, along with the rapid increase of the number of observed data points in recent years, the error bar of parameter C has become smaller and smaller, thus this feature has become more and more obvious.…”

Searching for cosmological preferred axis using cosmographic approach

“…The results for preferred direction in other models are presented for contrast. Point denotes the result of [33], point denotes the result of [38] and [28] ,point denotes the result of [50], point denotes the result of [37], point × denotes the result of [47], point • denotes the result of [47], .…”

“…5 dipole+monopole fit approach ( ∆µ µ = dcosθ + m) [38], [33], [37] 6 hemisphere comparison method [38], [28] 7 hemisphere comparison method…”

“…Ref. [37] have studied dipolar anisotropic expansion with cosmographic parameters, and found the preffered direction of (l = 309 • , b = −8.6 • ). The athours of [38] choosed two simple cosmological models, ΛCDM and ωCDM for the hemisphere comparison approach, and ΛCDM for the dipole fit.…”

Probing the isotropy of cosmic acceleration using different supernova samples

“…Generally, there are two different ways to study the possible anisotropy from SNe Ia. The first one is directly fitting the data to a specific anisotropic model (AM) [15][16][17]. Many anisotropic cosmological models have been proposed to match the observations, including the Bianchi I type cosmological model [15,18] and the Rinders-Finsler cosmological model [19].…”