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Perturbation level interacting dark energy model and its consequence on late-time cosmological parameters

In the present paper, we study the capability of interacting dark energy model with pure momentum transfer in the dark sector to reconcile tensions between low redshift observations and cosmic microwave background (CMB) results. This class of interacting model with pure momentum exchange introduces modifications to the standard model in the level of perturbation. We investigate the model by comparing to observational data, including integrated Sachs-Wolfe-galaxy cross-correlation, galaxy power spectrum, $f σ_8$, and CMB data. It is shown that this model can alleviate the observed tension between local and global measurements of $σ_8$. According to our results, the best fit value of $σ_8$ for interacting model is $0.700$, which is lower than the one for $Λ$CDM model and also is consistent with low redshift observations. Furthermore, we perform a forecast analysis to find the constraints on parameters of the interacting model from future experiments.