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A novel approach to cosmological non-linearities as an effective fluid

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arxiv 2410.15295 v2 pith:QWEHHCHP submitted 2024-10-20 astro-ph.CO gr-qc

classification astro-ph.COgr-qc
keywords cosmologicalmodelparameterseffectivefluidslambdasigmaabundance
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abstract

We propose a two parameters extension of the flat $\Lambda$CDM model to capture the impact of matter inhomogeneities on our cosmological inference. Non virialized but non-linearly evolving overdense and underdense regions, whose abundance is quantified using the Press-Schechter formalism, are collectively described by two effective perfect fluids $\rho_{\rm{c}},\rho_{\rm{v}}$ with non vanishing equation of state parameters $w_{\rm{c,v}}\neq 0$. These fluids are coupled to the pressureless dust, akin to an interacting DM-DE scenario. The resulting phenomenology is very rich, and could potentially address a number of inconsistencies of the standard model, including a simultaneous resolution of the Hubble and $\sigma_8$ tensions. To assess the viability of the model, we set initial conditions compatible to the Planck 2018 best fit $\Lambda$CDM cosmology and fit its additional parameters using SN~Ia observations from DESY5, BAO distances from DESI DR2 and a sample of uncorrelated $f\sigma_8$ measurements. Our findings show that backreaction effects from the cosmic web could restore the concordance between early and late Universe cosmological probes.

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Cited by 4 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. The matter with(in) CPL

    astro-ph.CO 2025-05 conditional novelty 5.0 of 10

    A model where ordinary matter acquires a negative effective pressure below z_t about 1.1 matches current cosmological data as well as the standard CPL dark energy model, without phantom crossing.

  2. Sign Switching in Dark Sector Coupling Interactions as a Candidate for Resolving Cosmological Tensions

    astro-ph.CO 2025-01 conditional novelty 5.0 of 10

    A sign-switching dark-sector coupling, fitted to CMB, DESI BAO, and supernova data, can simultaneously raise H0 and lower S8, but the preference over LambdaCDM depends on using SH0ES-calibrated supernovae.

  3. Dark Energy Is Not That Into You: Variable Couplings after DESI DR2 BAO

    astro-ph.CO 2025-08 conditional novelty 4.0 of 10

    With DESI DR2 data, one interacting dark sector model with a time-dependent coupling shows a nonzero coupling at more than 95% CL, but Bayesian evidence still favors Lambda-CDM.

  4. Encyclopedia of Astrophysics: The Expanding Universe

    astro-ph.CO 2025-09 unverdicted novelty 1.0 of 10

    An encyclopedia chapter restating the standard derivations of cosmic expansion: Hubble's law from the cosmological principle, the Friedmann equations, distances, and horizons.

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