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arXiv · 2606.17749

Alleviating the Hubble tension with the $\Lambda_{\omega_s}$CDM model

Youri Carloni
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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 $H_0 = 71.51^{+0.72(1.43)}_{-0.74(1.46)}$ km/s/Mpc, alleviating \emph{de facto} the Hubble tension.

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Youri Carloni. 2026-06-16. Alleviating the Hubble tension with the $\Lambda_{\omega_s}$CDM model. https://arxiv.org/abs/2606.17749

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