2023/11/24 by Deng Wang, Olga Mena, Wang, Deng +1
Physics and Astronomy · #Astronomy and Astrophysical Research #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Radio Astronomy Observations and Technology
paper · pdf · doi:10.48550/arxiv.2311.14423
openalex publication_date 2023/11/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Current cosmological tensions show that it is crucial to test the predictions from the canonical ΛCDM paradigm at different cosmic times. One very appealing test of structure formation in the universe is the growth rate of structure in our universe f, usually parameterized via the growth index γ, with f≡ Ωm(a)γ and γ≃ 0.55 in the standard ΛCDM case. Recent studies have claimed a suppression of the growth of structure from a variety of cosmological observations, characterized by γ>0.55. By employing different self-consistent growth parameterizations schemes, we show here that γ<0.55, obtaining instead an enhanced growth of structure today. This preference reaches the 3σ significance using Cosmic Microwave Background observations, Supernova Ia and Baryon Acoustic Oscillation measurements. The addition of Cosmic Microwave Background lensing data relaxes such a preference to the 2 σ level, since a larger lensing effect can always be compensated with a smaller structure growth, or, equivalently, with γ>0.55. We have also included the lensing amplitude A\rm L as a free parameter in our data analysis, showing that the preference for A\rm L>1 still remains, except for some particular parameterizations when lensing observations are included. We also not find any significant preference for a multipole dependence of A\rm L. To further reassess the effects of a non-standard growth, we have computed by means of N-body simulations the dark matter density fields, the dark matter halo mass functions and the halo density profiles for different values of γ. Future observations from the Square Kilometer Array, reducing by a factor of three the current errors on the γ parameter, could finally settle the issue.