Abstract
Two types of interacting dark energy models are investigated using the type Ia supernova (SNIa), observational $H(z)$ data (OHD), cosmic microwave background (CMB) shift parameter and the secular Sandage-Loeb (SL) test. We find that the inclusion of SL test can obviously provide more stringent constraint on the parameters in both models. For the constant coupling model, the interaction term including the SL test is estimated at $\delta=-0.01 \pm 0.01 (1\sigma) \pm 0.02 (2\sigma)$, which has been improved to be only a half of original scale on corresponding errors. Comparing with the combination of SNIa and OHD, we find that the inclusion of SL test directly reduces the best-fit of interaction from 0.39 to 0.10, which indicates that the higher-redshift observation including the SL test is necessary to track the evolution of interaction. For the varying coupling model, we reconstruct the interaction $\delta (z)$, and find that the interaction is also negative similar as the constant coupling model. However, for high redshift, the interaction generally vanishes at infinity. The constraint result also shows that the $\Lambda$CDM model still behaves a good fit to the observational data, and the coincidence problem is still quite severe. However, the phantom-like dark energy with $w_X<-1$ is slightly favored over the $\Lambda$CDM model.
Highlights
The SL test is in the inaccessible redshift zone for recent observations, such as the SNIa, observational H (z) data (OHD), and baryonic acoustic oscillation (BAO) at z < 2 and the cosmic microwave background (CMB) at z 1090
For the constant coupling model, the current observation combinations in the two sets of priors both give a weak interaction term, which is consistent with previous results [22]
By including the simulated SL test data, we find that they can more stringently constrain the corresponding parameters; the interaction in the WMAP-9 priors is δ = −0.01 ± 0.01 (1σ ) ± 0.02 (2σ ), which has been improved to be only half of the original scale on the errors
Summary
Different from the varying model, a constant coupling model with constant interaction term is provided [18,19] in which the matter density may not follow the common relationship ρm ∝ a−3. For the varying coupling model, investigations [23–25] found that SNIa and BAO data cannot provide stringent constraints on the parameter ξ until inclusion of the CMB data. One of them is to collect the secular variation of the expansion rate during the evolution of the universe from the wavelength shift of a quasar (QSO), Lyα absorption lines. This observation is usually named the Sandage–Loeb (SL) test.
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