Alleviating the Hubble tension with the ${\Lambda }_{{\omega }_s}$CDM model

Abstract

We formulate a novel extension of the $\Lambda$CDM model, named ${\Lambda }_{{\omega }_s}$CDM, in which we consider an additional term at early times in order to alleviate the Hubble tension. This additional component, referred to as \emph{matter with pressure}, indicates a barotropic fluid that is subdominant to dust and radiation as the Universe expands, thereby recovering the $\Lambda$CDM paradigm at late times. We constrain the ${\Lambda }_{{\omega }_s}$CDM cosmology by performing a Markov Chain Monte Carlo analysis with Planck 2018 CMB, DESI DR2, and Pantheon+\texttt{SH0ES} data. The results suggest that the barotropic factor and the normalized density of the new fluid are given, respectively, by ${\omega }_s=0.294_{-0.004(0.023)}^{+0.014(0.015)}$ and $10^5{\Omega }_s=1.62_{-0.56(0.91)}^{+0.36(1.02)}$. With these two additional parameters, the Hubble constant is increased to $H_0=71.51_{-0.74(1.46)}^{+0.72(1.43)}$ km/s/Mpc, alleviating \emph{de facto} the Hubble tension.

Proceeding AstroMarche2 conference, September 2025, Accepted for publication in IJMPA, 7 pages, 2 figures, 1 table