S₈ Tension in the Context of Dark Matter–Baryon Scattering

Abstract

We explore an interacting dark matter (IDM) model that allows for a fraction of dark matter (DM) to undergo velocity-independent scattering with baryons. In this scenario, structure on small scales is suppressed relative to the cold DM scenario. Using the effective field theory of large-scale structure, we perform the first systematic analysis of BOSS full-shape galaxy clustering data for the IDM scenario, and we find that this model ameliorates the S 8 tension between large-scale structure and Planck data. Adding the S 8 prior from the Dark Energy Survey (DES) to our analysis further leads to a mild ∼3σ preference for a nonvanishing DM–baryon scattering cross section, assuming ∼10% of DM is interacting and has a particle mass of 1 MeV. This result produces a modest ∼20% suppression of the linear power at k ≲ 1 h Mpc−1, consistent with other small-scale structure observations. Similar scale-dependent power suppression was previously shown to have the potential to resolve S 8 tension between cosmological data sets. The validity of the specific IDM model explored here will be critically tested with upcoming galaxy surveys at the interaction level needed to alleviate the S 8 tension.

The Atacama Cosmology Telescope: A Measurement of the DR6 CMB Lensing Power Spectrum and Its Implications for Structure Growth

“…The possibility remains that new physics suppresses structure only at very low redshifts, z < 1, or on nonlinear scales, k > 0.2h Mpc −1 , to which our CMB lensing measurements are much less sensitive than current cosmic shear, galaxy-galaxy lensing, or galaxy clustering constraints. An example of such physics could be the small-scale matter power spectrum suppression proposed in Amon & Efstathiou (2022) or He et al (2023) (along with systematics in CMB lensing cross-correlation analyses); modified gravity effects that become important at only very low redshifts are another example, although these need to be consistent with expansion and redshift-space distortion measurements.…”

The Atacama Cosmology Telescope: DR6 Gravitational Lensing Map and Cosmological Parameters

“…Different probes of the late universe access different redshifts or cosmic epochs (see Figure 1) and are also sensitive to different scales. Consequently, differences among the inferred values of σ 8 from various late-universe probes or with the early-universe prediction based on CMB anisotropies can hint at possibilities such as (1) nonstandard redshift evolution of the growth of structure, possibly due to modifications of general relativity (e.g., Pogosian et al 2022;Nguyen et al 2023); (2) a nonstandard power spectrum of matter fluctuations, e.g., due to axion dark matter (e.g., Rogers et al 2023) or dark matter-baryon scattering (e.g., He et al 2023); (3) incorrect modeling of small-scale fluctuations, e.g., due to nonlinear biasing (for galaxy observables) or baryonic feedback (for lensing observables; e.g., Amon & Efstathiou 2022); or (4) unaccounted-for systematic effects in one or more of these measurements. By providing a measurement of σ 8 with CMB lensing, we probe mainly linear scales with information from a broad range of redshifts z ∼ 0.5-5, which peaks around z = 2 as shown in Figure 1.…”

Seven Hints That Early-Time New Physics Alone Is Not Sufficient to Solve the Hubble Tension

“…Dark scattering-type scenarios studied in the literature include DM-DE scattering [293,, DM-photon scattering [83,[717][718][719], DM-neutrino scattering [71,[720][721][722][723][724], DM-baryon scattering [725][726][727][728][729][730][731][732][733][734][735], DM self-scattering and scattering with dark radiation [66,136,[736][737][738][739][740][741], "multi-interacting DM" scenarios featuring multiple similar interactions simultaneously [742], and DEbaryon scattering [743][744][745][746][747].…”