Free-Streaming Neutrinos in the Early Universe

Speaker(s) Benjamin Wallisch (Stockholm University & UT Austin)

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Standard Model neutrinos decoupled from the primordial plasma about one second after the big bang and have been free-streaming through the cosmos ever since. This leaves a subtle imprint in the baryon acoustic oscillations as observed in the cosmic microwave background (CMB) and large-scale structure (LSS) of the universe. Through careful theoretical considerations of the underlying physics and observables, we have been able to extract and measure the neutrino-induced phase shift in current CMB and LSS observations. In this talk, I will present the theoretical background, new data analyses and forecasts for the free-streaming nature of neutrinos, and discuss some implications for physics beyond the Standard Model.