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Michael James Wilson (Institute of Astronomy, U. Edinburgh) "Extracting precision tests of gravity from the intricate pattern of galaxies"
January 10, 2017 @ 4:00 pm - 5:00 pm
Galaxy redshift surveys deliver increasingly precise tests of gravity on cosmological scales and shed light on the uncertain nature of Dark Energy. I will present the VIPERS (http://vipers.inaf.it) census of the galaxy distribution at redshift 0.8 and describe its consistency with the expansion history and rate of gravitational collapse predicted by General Relativity and a Planck (2015) cosmology. This is facilitated by the anisotropy of the observed clustering, which is sensitive to both the coherent infall of galaxies towards clusters and the assumption of an expansion history differing from the true one.
I will then present the results of including a simple density transform prior to this conventional analysis, which suppresses the most massive structures and extends the validity of the simplest models. Moreover, this has been shown to amplify signatures of modified gravity in ‘shielded’ theories and contains information beyond that available to the power spectrum. To do so requires correcting for many systematics that are characteristic of high-redshift surveys. I will describe the properties common to VIPERS, eBOSS and DESI and the potential of a density-weighted analysis with these next-generation surveys.
Finally, tests of gravity have predominantly focused on the large-scale velocities of galaxies to date, but that of clusters is imprinted on the Cosmic Microwave Background by the kinetic Sunyaev-Zel’dovich effect. The Simons Observatory and CMB-S4 experiments represent ideal test-beds for exploring the latter. I will discuss this and other future avenues for revealing the properties of Dark Energy with large-scale structure.