Do we need soft cosmology?

Abstract

We examine the possibility of "soft cosmology", namely small deviations from the usual framework due to the effective appearance of soft-matter properties in the Universe sectors. One effect of such a case would be the dark energy to exhibit a different equation-of-state parameter at large scales (which determine the universe expansion) and at intermediate scales (which determine the sub-horizon clustering and the large scale structure formation). Concerning soft dark matter, we show that it can effectively arise due to the dark-energy clustering, even if dark energy is not soft. We propose a novel parametrization introducing the "softness parameters" of the dark sectors. As we see, although the background evolution remains unaffected, due to the extreme sensitivity and significant effects on the global properties even a slightly non-trivial softness parameter can improve the clustering behavior and alleviate e.g. the $f{\sigma }_8$ tension. Lastly, an extension of the cosmological perturbation theory and a detailed statistical mechanical analysis, in order to incorporate complexity and estimate the scale-dependent behavior from first principles, is necessary and would provide a robust argumentation in favour of soft cosmology.

5 pages, 2 figures

References in corpus (6)

• Dynamics of dark energy
• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• Beyond the Cosmological Standard Model
• Testing cosmological structure formation using redshift-space distortions
• The Nature of Primordial Fluctuations from Anisotropic Inflation
• Fractal Analysis of the UltraVISTA Galaxy Survey

Cited by in corpus (4)

• Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies
• Gravitationally Induced Particle Production through a Nonminimal Torsion-Matter Coupling
• A short review on clustering dark energy
• Gravitational Wave Propagation and Polarizations in the Teleparallel analog of Horndeski Gravity