Presented By: Leinweber Center for Theoretical Physics
Cosmology, Astro seminar | Massive neutrinos and cosmic composition
Zach Weiner (Perimeter)
Cosmological observations provide a leading method to measure the only unknown mass parameters in the Standard Model---the neutrino masses, whose measurement is a major goal of experiments in the coming decade. Recent data, however, hint at an unexpected incompatibility with the expected cosmological signatures of massive neutrinos, even if they were as light as allowed by neutrino oscillation experiments. I will describe the physical effects of massive neutrinos, clarifying the distinct roles of geometry and the growth of structure in determining joint constraints from various cosmological observations. Highlighting the importance of geometry, discrepancies in current measurements of the late-time expansion history lead to surprisingly tight constraints on neutrino masses for some dataset combinations, but for others instead yield marginal detections thereof. I will also comment on the implications of these findings for the possibility of nonminimal neutrino physics at play in the late Universe.