Redshift drift exploration for interacting dark energy
Jia-Jia Geng, Yun-He Li, Jing-Fei Zhang, Xin Zhang
TL;DR
The paper evaluates how future redshift-drift measurements from the Sandage-Loeb test, using a CODEX-like spectrograph, can constrain interacting dark energy models across four coupling forms. By simulating SL data based on fiducial fits to current SN, BAO, CMB, and $H_0$ data, it shows that SL observations substantially reduce degeneracies and improve constraints on $\Omega_m$ and $H_0$ (roughly $60\%$ and $30$-$40\%$), with modest gains for $w$ and $\gamma$. In a forward-looking scenario with WFIRST-like SN/BAO data, SL data further enhance precision, especially for the interaction parameter $\gamma$ in at least one model, indicating SL drift measurements are a crucial supplement to geometric probes. Overall, the study demonstrates the SL test’s potential to significantly sharpen cosmological constraints on interacting dark energy and guide future observational strategies.
Abstract
By detecting redshift drift in the spectra of Lyman-$α$ forest of distant quasars, Sandage-Loeb (SL) test directly measures the expansion of the universe, covering the "redshift desert" of $2 \lesssim z \lesssim5$. Thus this method is definitely an important supplement to the other geometric measurements and will play a crucial role in cosmological constraints. In this paper, we quantify the ability of SL test signal by a CODEX-like spectrograph for constraining interacting dark energy. Four typical interacting dark energy models are considered: (i) $Q=γHρ_c$, (ii) $Q=γHρ_{de}$, (iii) $Q=γH_0ρ_c$, and (iv) $Q=γH_0ρ_{de}$. The results show that for all the considered interacting dark energy models, relative to the current joint SN+BAO+CMB+$H_0$ observations, the constraints on $Ω_m$ and $H_0$ would be improved by about 60\% and 30--40\%, while the constraints on $w$ and $γ$ would be slightly improved, with a 30-yr observation of SL test. We also explore the impact of SL test on future joint geometric observations. In this analysis, we take the model with $Q=γHρ_c$ as an example, and simulate future SN and BAO data based on the space-based project WFIRST. We find that in the future geometric constraints, the redshift drift observations would help break the geometric degeneracies in a meaningful way, thus the measurement precisions of $Ω_m$, $H_0$, $w$, and $γ$ could be substantially improved using future probes.