Relieving the S8S_8 Tension: Exploring the Surface-type DBI Model as a Dark Matter Paradigm

Abstract

Recent observations of weak gravitational lensing surveys indicate a smoother Universe compared to the predictions of the Cosmic Microwave Background (CMB). This is known as Οƒ8\sigma_8 tension or S8S_8 tension, where Οƒ8\sigma_8 represents the present root-mean-square matter fluctuation averaged over a sphere of radius 8hβˆ’1Mpc8 h^{-1} \mathrm{Mpc} and S8≑σ8Ξ©m/0.3S_8 \equiv \sigma_8\sqrt{\Omega_m/0.3}. In this letter, we investigate a kind of general Dirac-Born-Infeld (DBI) Lagrangian referred as surface-type DBI (s-DBI) model. We have found that, up to the linear order, the constraints on the s-DBI model with CMB from Planck2018 and low-redshift probes (WL and GC) yield S8=0.7685βˆ’0.0066+0.0077S_8= 0.7685_{-0.0066}^{+0.0077} and S8=0.766βˆ’0.0376+0.0471S_8=0.766_{-0.0376}^{+0.0471}, respectively, which are not only self-consistent but also consistent with the values derived from most low-redshift probes. Furthermore, we provide an outlook for searching the non-linear effects of this model, which could be helpful to resolve other issues by Cold Dark Matter on small scales.Comment: Submitted, comments welcom

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