Combining measurements of the Cosmic Microwave Background with galaxy clustering to probe the nature of gravity and neutrinos in the universe.

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Upcoming galaxy surveys and Cosmic Microwave Background (CMB) experiments will shortly produce complementary 3D maps of the distribution and motion of matter in unparalleled detail. This presents an unprecedented opportunity to address some of the most fundamental and profound questions in astrophysics, to understand: the origins of the cosmos’ accelerating expansion, if Einstein’s general theory of relativity (GR) breaks down on cosmological scales, and the nature of dark matter and neutrinos. Scientists at Cornell University propose to expand the armory of discriminating tools spanning both dense (clusters of galaxies) and under-dense (void) environments in which deviations from GR and the effects of neutrino masses manifest differently. This proposal will also include an “Afterschool Universe” program for school students in upstate New York that introduces and applies basic astronomical and physics concepts.This project is tailored to fully utilize the range of astrophysical scales, tracers and environments made newly accessible by the next generation large scale structure and CMB surveys. Products from this research will include the highest signal-to-noise pairwise kinematic Sunyaev-Zel’dovich (kSZ) measurements to-date by analyzing the final CMB maps from the Atacama Cosmology Telescope (ACT) combined with Year-1 survey data from the Dark Energy Spectroscopic Instrument (DESI). The work will also use simulations to yield accurate predictions of the effects on the pairwise kSZ signal and void redshift space distortion (RSD) profile, from a variety of modified gravity and massive neutrino cosmologies. It will involve analytic work to extend Lagrangian perturbation theory and Gaussian streaming model approaches to accurately model RSD correlations in dark sector theories, the measurement of void RSD correlations from the DESI Year-1 data and cosmological constraints from them. Finally, this project includes theoretical work to investigate the potential of combining weak lensing data from the Vera Rubin Observatory’s Legacy Survey of Space and Time and/or CMB lensing observations, and DESI RSD measurements, in order to break degeneracies and reveal distinctive signatures of the dark sector in voids.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.