Revealing Cosmic Structure Growth and the Early Universe with the CMB Backlight

With pioneering measurements of Cosmic Microwave Background (CMB) gravitational lensing and scattering, this project will address two of the most important questions in cosmology.Do we understand how cosmic structure grows over time? The growth of large-scale structure with time is one of the most powerful tests of our standard cosmological model and of new physics. Intriguingly, claims of tensions between observations of structure growth and standard model predictions persist. By measuring CMB lensing spectra and cross-correlations with the Simons Observatory (SO) that are five times more precise than the current state-of-the-art, we will place the tightest constraints on structure growth over a wide redshift range. Our ERC-funded innovations, which will enable the use of data that are usually discarded and get more from the data with new statistics, will be crucial for such powerful results. Our work will definitively test whether the standard cosmological model correctly predicts structure growth out to high redshifts z~5.5 and will determine or tightly bound the unknown neutrino mass.What is the physics of the early universe? Measurements of the non-Gaussianity of the primordial density perturbations are a unique test of whether the very early universe is described by the simplest inflation models or by more complex new physics. By reconstructing the cosmic velocity field using the kinetic Sunyaev-Zel’dovich (kSZ) scattering effect in SO data and correlating it with galaxies, my team will obtain powerful constraints on non-Gaussianity (3-5 times tighter than the state-of-the-art) and provide new insights into early-universe physics. With kSZ measurements we will also probe astrophysics at early times: we will provide leading constraints on the duration of reionization by detecting, for the first time, the kSZ four-point function with SO. Our ERC-funded effort will advance kSZ science from first demonstrations to a mature probe of the early universe.