Joint cosmology seminar at Tufts:

Tuesday, April 30, 2024, 2:30 pm
\large\sf Zoom link will be distributed to joint cosmology seminar mailing list. See\\
https://cosmos.phy.tufts.edu/mailman/listinfo/cosmology-seminar to join.\\Or watch with us in Room 402, 574 Boston Ave.,
Tufts University
Refreshments at 2:00 outside the building, at the corner of Harvard St. and Boston Ave.

Dark Radiation with Baryon Acoustic Oscillations from DESI 2024 and the H0 tension

Itamar Allali
Brown

Abstract:

We investigate the presence of extra relativistic degrees of freedom in the early Universe, contributing to the effective number of neutrinos $N_{eff}$, as $\Delta N_{eff}$ = $N_{eff}-3.044 \ge 0$, in light of the recent measurements of Baryon Acoustic Oscillations (BAO) by the DESI collaboration. We analyze one-parameter extensions of the $\Lambda$CDM model where dark radiation (DR) is free streaming or behaves as a perfect fluid, due to self-interactions. In this talk, I will report on the significant relaxation of upper bounds on $\Delta N_{eff}$ with respect to previous BAO data from SDSS+6dFGS. I will comment on the effects of constraints from primordial element abundances. Considering also dark radiation produced after the epoch of Big Bang Nucleosynthesis (BBN), I will discuss the impacts of these new data on the Hubble tension, and potential evidence for dark radiation beyond $\Lambda$CDM.