2021/07/19 by Jie Zheng, Yun Chen, Zheng, Jie +3
Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Gamma-ray bursts and supernovae #Pulsars and Gravitational Waves Research
paper · pdf · doi:10.48550/arxiv.2107.08916
openalex publication_date 2021/07/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
In the framework of a phenomenological cosmological model with the assumption of ρX ∝ ρm aξ (ρX and ρm are the energy densities of dark energy and matter, respectively.), we intend to diagnose the cosmic coincidence problem by using the recent samples of Type Ia supernovae (SNe Ia), baryon acoustic oscillation (BAO) and cosmic microwave background (CMB). ξ is a key parameter to characterize the severity of the coincidence problem, wherein ξ=3 and 0 correspond to the ΛCDM scenario and the self-similar solution without the coincidence problem, respectively. The case of ξ= Constant has been investigated in the previous studies, while we further consider the case of ξ(z) = ξ0 + ξz*(z)/(1+z) to explore the possible evolution. A joint analysis of the Pantheon SNe Ia sample with the recent BAO and CMB data figures out that ξ=3.28±0.15 in the case of ξ= Constant at 68% confidence level (CL), in addition, ξ0 = 2.78-1.01+0.28 and ξz = 0.93-0.91+1.56 in the case of ξ(z) at 68% CL. It implies that the temporal evolution of the scaling parameter ξ is accepted by the joint sample at 68% CL; however, the joint sample also cannot distinguish whether the scaling parameter ξ is variable or not at 95% CL. Moreover, the ΛCDM scenario is accepted by the joint sample at 95% CL in both cases, and the coincidence problem still exists. In addition, we apply the Bayesian evidence to compare the models with the analysis of the joint sample, it turns out that the ΛCDM scenario is most supported by the joint sample; furthermore, the joint sample prefers the scenario with a constant ξ to the one with a variable ξ(z).