Ravi ShethMartino, Matthew C2023-05-222009-12-032009-12-222009-12-03https://repository.upenn.edu/handle/20.500.14332/32372Recent observations indicate that the expansion rate of the universe is accelerating. For this to be the case, either the universe needs to be dominated by an unusual substance dubbed "dark energy", or our model of gravity needs to be changed. There are many consequences that result from modifying gravity, and these need to be considered when we consider a modified gravity model. In particular, this thesis will examine environmental effects in standard gravity with an interest in understanding how these effects might be changed in a modified gravity model, and will also consider the formation of clusters and voids in a particular modified gravity model with the goal of calculating mass functions that can be used in halo model calculations.Large scale structurecosmologymodified gravityAstrophysics and AstronomyCosmology, Relativity, and GravityDissertation/Thesis