2025/08/15 by R. Noemí Villalobos, Yerko Vásquez, Villalobos, R. Noemí +5 · 1 citation
Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae #General Relativity and Quantum Cosmology (gr-qc)
paper · doi:10.48550/arxiv.2508.11614
openalex publication_date 2025/08/15 · openalex created_date 2026/03/27 · openalex updated_date 2026/07/28
We investigate whether viscous cold dark matter (vCDM) in a Λ-dominated FLRW universe can alleviate the Hubble tension while satisfying thermodynamic constraints, examining both flat and curved geometries. We model vCDM with bulk viscosity ζ= ζ0 (Ωvc/Ωvc0)m, where m determines the viscosity evolution and Ωvc is the density parameter of vCDM. We explore two particular scenarios: constant viscosity (m=0), and variable viscosity (m free). Using Bayesian inference, we constrain these models with the latest datasets: the Pantheon+ SN Ia sample (both with SH0ES calibration, PPS, and without it, PP), H(z) measurements from CC and BAO as separate datasets, and a Gaussian prior on H0 from 2022 SH0ES baseline, H0=73.04 ± 1.04 km/s/Mpc (R22 prior). We compare the models via information criteria such as AIC, BIC, DIC, and Bayesian evidence. Our results reveal that the Hubble tension persists, although it shows partial alleviation (∼ 1σ tension) in all investigated scenarios when local measurements are included. For the flat m=0 case, the joint analysis yields H0 = 71.05+0.62-0.60 km/s/Mpc. Curved model initially favors ΩK0 > 0 (at more than 2σ), but this preference shifts toward flatness once the PPS+R22 prior are included. Notably, the current viscosity is constrained to ζ0 ∼ 106 Pa s in all scenarios, in agreement with the thermodynamic requirements. Although model selection via BIC and Bayesian evidence favors ΛCDM, AIC and DIC show mild support for viscous models in some datasets. Bulk viscous models moderately improve fits but neither resolve the Hubble tension nor outperform the ΛCDM model. To achieve more robust constraints, future analyses should incorporate CMB observations, which are expected to break parameter degeneracies involving m and ζ0.