Chen, Alice2020-09-032020-09-032020-09-032020-08-13http://hdl.handle.net/10012/16237Dark matter makes up around a quarter of the total energy density in the universe, but its identity remains elusive. Current ways of studying dark matter have centered around its macroscopic properties, such as density distribution and large scale structure formation. The halo model of large scale structure is an important tool that cosmologists use to study the phenomenological behaviour and nonlinear evolution of structure in the universe. However, it is well known that there is no simple way to impose conservation laws in the halo model. This can severely impair the predictions on large scales for observables such as weak lensing or the kinematic Sunyaev-Zel’dovich effect, which should satisfy mass and momentum conservation, respectively. For example, the standard halo model overpredicts weak lensing power spectrum by > 8% on scales > 20 degrees. To address this problem, we present an Amended Halo Model, explicitly separating the linear perturbations from compensated halo profiles. This is guaranteed to respect conservation laws, as well as linear theory predictions on large scales. We also provide a simple fitting function for the compensated halo profiles, and discuss the modified predictions for 1- halo and 2-halo terms, as well as other cosmological observations such as weak lensing power spectrum. Similar to previous and recent works centered around the halo model, this work is physically motivated and matches simulation data to a greater degree of accuracy than the standard halo model currently does. We compare our results to previous work, and argue that the amended halo model provides a more efficient and accurate framework to capture physical effects that happen in the process of large scale cosmological structure formation.enMaster Thesis