HEP Colloquia 2021

by Dr Riccardo Murgia (LUPM Montpellier)

Thursday 8 Apr 2021, 14:30 → 16:30 Europe/Rome

Online

Hitchhiker’s Guide to Cosmological Concordance

According to the standard cosmological (ΛCDM) model, the present universe is mainly composed of a cosmological constant, denoted by Λ, and by Cold DarkMatter (CDM). Such a paradigm is in tremendous agreement with Cosmic Microwave Background(CMB) and Large-Scale Structure (LSS) data, yet some tensions exist: namely, on the local, direct determinations of the expansion rate of the universe, H0, and the amplitude of the matter fluctuations today,σ8, which are ∼ 4−5σ higher and ∼2−3σ lower, respectively, compared to the values inferred from early universe observations within ΛCDM. Furthermore, the amount of gravitational lensing determined from the CMB temperature and polarization power spectra from Planckis∼2−3σ higher than that measured from the lensing potential reconstruction, and expected in ΛCDM. Finally, assuming purely CDM, cosmological N-body simulations show some limits in reproducing the observed astrophysical properties on (sub-)galactic scales. In the absence of fully satisfactory solutions within the CDM framework, and driven by the fact that the nature of the dark sector is still unknown, a number of alternative scenarios have emerged as a possible way to explain the discrepancies. I will discuss why these tensions could hint to new physics, outline paths towards restoring cosmological concordance, and present up-to-date bounds on some of the most promising proposed resolutions, such as early dark energy, sterile neutrinos, DM interacting with dark radiation, decaying DM

 

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