Institute for Advanced Study/Princeton University Early Universe/Cosmology Lunch Discussion

Abstract 1: Massive neutrinos suppress the growth of cosmic structure on small, non-linear, scales. There is thus much interest in using statistics beyond the power spectrum to tighten constraints on the neutrino mass by extracting additional information from these non-linear scales. In this talk, I will first explore the information in the non-linear matter field using the Quijote simulations. I will show how the matter power spectrum, halo mass function, and void size function can be combined to break degeneracies between cosmological parameters and give considerably tighter constraints on the neutrino mass compared to the power spectrum alone. I will then explore how much of this non-linear information we can expect to find in upcoming surveys which observe galaxy clustering and weak lensing. In turn, I will introduce the Half Dome simulations as a tool to study cross-correlations between large-scale structure and the cosmic microwave background. Finally, I will motivate field-level inference with differentiable forward modeling as a method to optimally extract information from cosmic structure.

Abstract 2: Observing the Universe at large scales, a considerable fraction of its volume is dominated by almost empty space. Alongside the luminous filamentary structures of the Universe, there are vast underdense zones commonly known as cosmic voids. Although essentially devoid of matter, voids enclose fundamental information about the cosmological framework. In this talk I will present the first cosmological constraints derived from the analysis of the void size function, i.e. the number of cosmic voids as a function of their radius. These results are obtained from the modeling of voids identified in the final BOSS DR12 data set, adopting a state-of-the-art methodology to take into account a number of observational effects. I will showcase the constraining power achieved on the main parameters of the $\Lambda$CDM and the $w$CDM models. This includes the first estimate of the parameters $H_0$ and $S_8 \equiv \sigma_8\sqrt{\Omega_{\rm m}/0.3}$ derived from cosmic voids, providing new insights on the rising tensions in Cosmology.