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arXiv · 2503.05208

Impact of Interacting Dark Energy on the Growth of Matter Density Perturbations: Observational Constraints from DESI and Multi-Probe Data

Fan Yang·Rongrong Zhai·Xiangyun Fu·Bing Xu·Kaiwen Liu·Chikun Ding·Yang Huang
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Abstract

We investigate the impact of a non-gravitational dark sector interaction on the growth of matter density perturbations within both the interacting $w$CDM and the dynamical Chevallier-Polarski-Linder (CPL) scenarios. For $w$CDM model, we develop a parameterization for the growth rate based on a second-order approximation for the growth index $\gamma$ that explicitly includes the coupling constant $\alpha$. Our analysis reveals a theoretical degeneracy: the coupling induces a correction $\Delta\gamma \simeq 1.1\alpha$ in both models, allowing an interacting dark energy model to mimic the growth index predicted by certain modified gravity theories. Then, we confront the models with the latest multi-probe observations, including the Pantheon+ sample of Type Ia supernovae, Baryon Acoustic Oscillation (BAO) data from the Sloan Digital Sky Survey (SDSS) and the second data release (DR2) of the Dark Energy Spectroscopic Instrument (DESI), Cosmic Microwave Background (CMB) measurements, Hubble parameter $H(z)$ data, and redshift-space distortion (RSD) measurements. Our analysis finds that the coupling constant is consistent with zero at approximately the $3\sigma$ and $2\sigma$ confidence levels for $w$CDM and CPL models, respectively, showing no definitive statistical evidence for a departure from the standard $\Lambda$CDM cosmology. The observational constraints strongly disfavor the region of parameter space where interacting dark energy can mimic modified gravity, restricting the growth index to a common approximate interval of $0.53 \lesssim \gamma \lesssim 0.60$ for both models. This reinforces the growth index as a robust diagnostic for distinguishing between a non-minimal interaction in the dark sector and a genuine modification of gravity with current data.

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Fan Yang, Rongrong Zhai, Xiangyun Fu, Bing Xu, Kaiwen Liu, Chikun Ding, Yang Huang. 2025-03-07. Impact of Interacting Dark Energy on the Growth of Matter Density Perturbations: Observational Constraints from DESI and Multi-Probe Data. https://arxiv.org/abs/2503.05208

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