Modelo com interação do sector escuro do Universo com acoplamento quadrático: viabilidade teórica e observacional

Abstract

Models proposing a non-gravitational interaction between dark energy (DE) and cold dark matter (CDM) have been extensively studied as alternatives to the standard cosmological model. A common approach to describing the DE-CDM coupling assumes it to be linearly proportional to the dark energy density. In this thesis, we consider the model with the interaction term Q = 3Hγρ2 x /(ρc +ρx). We show that for positive values of γ, this model predicts a future violation of the Weak Energy Condition (WEC) for the dark matter component, and for a specific range of negative values of γ, the CDM energy density can be negative in the past. In this work, we conducted two different analyses. In the first, we performed a parameter selection analysis for this model using data from Type Ia supernovae (SNe Ia) from the Pantheon sample, 30 measurements of H(z) from the Cosmic Chronometers (CC) sample, Baryon Acoustic Oscillations (BAO) from the DESI Data Release 1 (DR1), and Cosmic Microwave Background (CMB) data from the Planck collaboration, combined with a prior on the Hubble constant H0. Imposing a prior to ensure that the WEC is not violated, our model is consistent with ΛCDM within 2σ confidence levels (C.L.), but it exhibits a preference for smaller values of σ8, alleviating the σ8 tension between the CMB results from Planck 2018 and the cosmic shear observations from KiDS-1000. In the second analysis, we used data from SNe Ia from the Pantheon+ sample, 32 measurements of H(z) from the CC sample, BAO from DESI Data Release 2 (DR2), and CMB data from Planck. In this analysis, we considered the Equation of State (EoS) parameter ωx as a free parameter and included the WEC prior in the analyses as well. Our results are consistent within 2.5σ C.L. with the results from the DESI DR2 analysis for the ωCDM model.