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14:00 Andrew Jamieson (Stony Brook University)
Title: The separate universe from low to high densities
Abstract: Upcoming surveys will map out the large scale structure of the universe over the next decade, providing a wealth of data that could greatly improve our constraints on cosmological parameters and potentially give evidence of new physics in cosmology. There are, however, some challenges in relating what we can predict from theory to what we observe in large scale structure surveys. These challenges include the nonlinearity of cosmic structure formation and the bias of the objects (e.g. galaxies) that we have access to observationally. In this talk I will present some results from past work (arXiv:1812.08765 and arXiv:1909.05313) using separate universe simulations to address these difficulties. The first is a study of the effects of dynamical dark energy isocurvature on the bias of halos in simulations, while the second is a study of the bias of cosmic voids. I will also present results from a new application of separate universe methods to study the probability distribution function (PDF) of the smoothed density field in simulations. The linear response of this PDF to the presence of long wavelength density modes can be used to identify regions of the density field that are most sensitive to different cosmological parameters.
14:30 Xiaolong Du (Carnegie Observatories)
Title: Collision of Fuzzy Dark Matter Halos
Abstract: Fuzzy dark matter (FDM), sometimes called wave dark matter, is an attractive dark matter candidate. The FDM particle is extremely light, 10^{-20}~10^{-22} eV, leading to observable wave phenomena on sub-galactic scales, e.g. suppression of small-scale structure formation, and flat cores in the center of dark matter halos. In this talk, I will show some of our latest studies of colliding FDM halos. Using a high-accuracy pseudospectral code we develop, we simulate the merging process of two FDM halos. Comparing with collisionless cold dark matter, we find interesting phenomena that are unique to the FDM model, and which can potentially be used to look for FDM features in merging galaxies, thereby placing constraints on the particle mass.