Nonlinear gravity in the late Universe

James Mertens (York University)

May 30, 2019

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Abstract: Theoretical models of our Universe often rely on approximate treatments of gravity. In this talk, I will describe recent progress modelling spacetimes without such assumptions. This allows us to not only study the nonlinear behaviour of general relativity, but to probe the validity of fundamental assumptions underlying our cosmological models, such as the cosmological principle. This work provides some validation of our standard cosmological models, as well as a measure of the importance of relativistic effects. These relativistic effects can lead to biases in our cosmological inferences, affecting observations ranging from galaxy surveys to kSZ tomography.