Novel Approach to Cosmological Nonlinearities as an Effective Fluid

Area of Science:

• Cosmology
• Astrophysics
• Theoretical Physics

Background:

• The standard Lambda Cold Dark Matter (ΛCDM) model faces challenges, including the Hubble and σ8 tensions.
• Cosmic structures and matter inhomogeneities may impact cosmological inference beyond the standard model.

Purpose of the Study:

• To propose and test an extended cosmological model that incorporates the effects of matter inhomogeneities.
• To investigate if this new model can resolve existing cosmological tensions.

Main Methods:

• Developed a two-parameter extension of the flat ΛCDM model using effective fluids to describe cosmic web regions.
• Coupled these fluids to pressureless matter, simulating an interacting dark matter-dark energy scenario.
• Fit the model's parameters using supernova, Baryon Acoustic Oscillation, and fσ8 measurements, with initial conditions from Planck 2018 data.

Main Results:

• The proposed model, accounting for backreaction from the cosmic web, shows potential for resolving inconsistencies in the standard model.
• Demonstrated the possibility of a simultaneous resolution for the Hubble and σ8 tensions.
• Found that cosmic web effects can reconcile early and late Universe cosmological probes.

Conclusions:

• The extended cosmological model offers a promising alternative to the standard ΛCDM model.
• Backreaction effects from cosmic web inhomogeneities are crucial for cosmological concordance.
• This framework could provide a unified solution to major cosmological tensions.