Disentangling Massive Neutrino Cosmologies with Higher-Order Clustering Statistics

Free-streaming of cosmic neutrinos on small scales affects the distribution and growth of cosmic structures, allowing constraints on the sum of their masses from clustering studies. In this context, it is of particular interest to explore the contribution of higher-order clustering statistics, and in particular of the 3-point correlation function (3PCF), since it is the first order capable of quantifying the non-Gaussian properties of the Large-Scale Structure. In this Thesis, we investigate for the first time the possibility of disentangling massive neutrino cosmologies with the 3PCF. We measure the isotropic 3PCF ζ and the reduced 3PCF Q of halos in the Quijote simulations, which include neutrinos as particles, with Mν = 0.1, 0.2, and 0.4 eV. We develop a framework to quantify the detectability of massive neutrinos for different triangle configurations and shapes, finding that, as an effect of free-streaming, the largest signal is found in isosceles triangles on scales smaller than ∼ 30 h-1 Mpc, and in quasi-isosceles and squeezed triangles, increasing for decreasing redshift. For these configurations, we find that elongated triangles, tracing the filamentary structure of the cosmic web, are the most affected by neutrinos, with a 3PCF signal increasing with Mν. A complementary source of information comes from perpendicular configurations in Q. We also investigate whether the 3PCF can break the degeneracy between Mν and σ8 by measuring both ζ and Q for an additional set of Quijote halo catalogues with σ8 = 0.819, 0.849. We find that they respond to variations of Mν and σ8 differently as a function of triangle shapes and scales. In particular, the signature of neutrinos on perpendicular configurations in Q results significantly different in varying-σ8 cosmologies, and hence can be used to effectively break their degeneracy.