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Constraining Neutrino Mass with the Bispectrum

Massive neutrinos suppress the growth of structure below their free-streaming scale and leave an imprint on large-scale structure. Measuring this imprint allows us to constrain the sum of neutrino masses, Mnu, a key parameter in particle physics beyond the Standard Model. However, degeneracies among cosmological parameters, especially between Mnu and sigma8, limit the constraining power of standard two-point clustering statistics. I will present whether we can break these degeneracies and constrain Mnu with the next higher-order correlation function - the bispectrum. I first examine the redshift-space halo bispectrum of 800 N-body simulations from the HADES suite and demonstrate that the bispectrum helps break the Mnu-sigma8 degeneracy. Then I will present the full information content of the redshift-space halo bispectrum down to nonlinear scales using a Fisher matrix forecast of {Om, Ob, h, ns, sigma8, Mnu} with 22,000 N-body simulations of the Quijote suite. For kmax=0.5 h/Mpc, the bispectrum provides Om, Ob, h, ns, and sigma8 constraints 1.9, 2.6, 3.1, 3.6, and 2.6 times tighter than the power spectrum. For Mnu, the bispectrum improves the 1sigma constraint from 0.2968 to 0.0572 eV - over 5 times tighter than the power spectrum. Lastly, I will present ongoing projects that are laying down the framework for a full bispectrum analysis of DESI: including a comprehensive bias model, data compression for the bispectrum, paired-fixed simulations for the bispectrum, and efficient simulation-based inference methods.

Speaker: ChangHoon Hahn, UC Berkeley

Monday, 10/21/19


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