Probing gravity with redshift surveys

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Dr White will use analytical modeling, informed by a series of large, high precision N-body simulations, to better understand dark energy and the growth of structure in the cosmos. When their distances are estimated from their redshifts, galaxies on large scales appear to be more strongly clumped along the line of sight than in the tangential direction. This 'redshift distortion' depends on both the gravitational attraction between the galaxies and the effect of dark energy in accelerating the cosmic expansion. In General Relativity, the redshift distortion depends on the same combination of cosmological parameters as does weak gravitational lensing, but in other theories the two dependences differ. Dr White will use different underlying theories of gravity to run cosmological N-body simulations, then 'observe' these, to explore how redshift distortions can best be used in testing alternatives to General Relativity. He and his team will also develop a perturbation theory to follow galaxy clustering into a mildly nonlinear regime, where the velocity perturbations are no longer strictly proportional to the density fluctuations. The project will address outstanding issues in the interpretation of surveys, the modeling of redshift space distortions, and the connection between galaxies and dark matter.A graduate student will be trained through participating in the research. Tests of General Relativity have broad implications throughout physics and astronomy. Dr White will continue his public outreach talks and popular articles on cosmology, and supply educational information on public web sites.