Reduced Hubble Tension in Dark Radiation Models after DESI 2024
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| Natura: | Preprint |
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2024
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| author | Allali, Itamar J. Notari, Alessio Rompineve, Fabrizio |
| author_facet | Allali, Itamar J. Notari, Alessio Rompineve, Fabrizio |
| contents | We investigate the presence of extra relativistic degrees of freedom in the early Universe, contributing to the effective number of neutrinos $N_\text{eff}$, as $ΔN_\text{eff}\equiv N_\text{eff}-3.044\geq 0$, in light of the recent measurements of Baryon Acoustic Oscillations (BAO) by the DESI collaboration. We analyze one-parameter extensions of the $Λ$CDM model where dark radiation (DR) is free streaming or behaves as a perfect fluid, due to self-interactions. We report a significant relaxation of upper bounds on $ΔN_\text{eff}$, with respect to previous BAO data from SDSS+6dFGS, when additionally employing Planck data (and supernovae data from Pantheon+), setting $ΔN_\text{eff}\leq 0.39$ ($95\%$ C.L.) for free streaming DR, and a very mild preference for fluid DR, $ΔN_\text{eff} = 0.221^{+0.088}_{-0.18}$ ($\leq 0.46$, $95\%$ C.L.). Applying constraints from primordial element abundances leads to slightly tighter constraints on $ΔN_\text{eff}$, but they are avoided if DR is produced after Big Bang Nucleosynthesis (BBN). For fluid DR we estimate the tension with the SH$_0$ES determination of $H_0$ to be less than $3σ$ and as low as $2σ$, and for free-streaming DR the tension is below $3σ$ if production occurs after BBN. This lesser degree of tension motivates a combination with SH$_0$ES in these cases, resulting in a $4.4σ-5σ$ evidence for dark radiation with $ΔN_\text{eff}\simeq 0.6$ and large improvements in $χ^2$ over $Λ$CDM, $-18\lesssim Δχ^2\lesssim -25$. Upcoming data releases by DESI and other CMB and LSS surveys will decisively confirm or disfavour this conclusion. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2404_15220 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Reduced Hubble Tension in Dark Radiation Models after DESI 2024 Allali, Itamar J. Notari, Alessio Rompineve, Fabrizio Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology We investigate the presence of extra relativistic degrees of freedom in the early Universe, contributing to the effective number of neutrinos $N_\text{eff}$, as $ΔN_\text{eff}\equiv N_\text{eff}-3.044\geq 0$, in light of the recent measurements of Baryon Acoustic Oscillations (BAO) by the DESI collaboration. We analyze one-parameter extensions of the $Λ$CDM model where dark radiation (DR) is free streaming or behaves as a perfect fluid, due to self-interactions. We report a significant relaxation of upper bounds on $ΔN_\text{eff}$, with respect to previous BAO data from SDSS+6dFGS, when additionally employing Planck data (and supernovae data from Pantheon+), setting $ΔN_\text{eff}\leq 0.39$ ($95\%$ C.L.) for free streaming DR, and a very mild preference for fluid DR, $ΔN_\text{eff} = 0.221^{+0.088}_{-0.18}$ ($\leq 0.46$, $95\%$ C.L.). Applying constraints from primordial element abundances leads to slightly tighter constraints on $ΔN_\text{eff}$, but they are avoided if DR is produced after Big Bang Nucleosynthesis (BBN). For fluid DR we estimate the tension with the SH$_0$ES determination of $H_0$ to be less than $3σ$ and as low as $2σ$, and for free-streaming DR the tension is below $3σ$ if production occurs after BBN. This lesser degree of tension motivates a combination with SH$_0$ES in these cases, resulting in a $4.4σ-5σ$ evidence for dark radiation with $ΔN_\text{eff}\simeq 0.6$ and large improvements in $χ^2$ over $Λ$CDM, $-18\lesssim Δχ^2\lesssim -25$. Upcoming data releases by DESI and other CMB and LSS surveys will decisively confirm or disfavour this conclusion. |
| title | Reduced Hubble Tension in Dark Radiation Models after DESI 2024 |
| topic | Cosmology and Nongalactic Astrophysics High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2404.15220 |