Cosmological Information Disappearing Behind Origami Folds and Optimal Statistics to Analyze What Remains

Mark Neyrinck (Johns Hopkins)

November 03, 2014

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Abstract: Structures in the Universe like galaxies, and filaments and clusters of galaxies, are essential components of the arrangement of matter on large scales. They form in analogy to the origami folding of a sheet of dark matter. I will discuss some new results into the kinds of structures that form, and the spins that can arise within them, that come from an “origami approximation” in which the Lagrangian-to-Eulerian displacement field is a piecewise isometry. One practical motivation for studying this is for weak-lensing intrinsic alignments. While these structures are fascinating, and conveniently allow observers like us to exist, they also make it harder to extract cosmological information on small scales. This nonlinear-scale information is sensitive, for example, to galaxy formation details, exotic models of dark energy, parameters of inflation, neutrino masses, and whether the dark matter is cold or warm. I will discuss a “transformational” method for recovering this information, using a nonlinear transformations such as a logarithm, or more generally, PDF-Gaussianization.