Upadhyay, Vikram (2017) Testing Modified Gravity with the Sunyaev Zel'dovich Effect. [Magistrali biennali]
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): In this thesis, we present a method to test modified-gravity models. Growth of large-scale structures is directly related to the governing gravity theory. Any modification to the General Relativity equations, suggested by modified gravity models, will have an affect on the growth of the structures. This change in the dynamics of formation of structures can be tested using tools of cosmological probe, like the Sunyaev-Zel’dovich effect. When a low-energy CMB photon travels through the intracluster medium (ICM), it receives an average boost of energy after collisions with the high energy cluster electrons. This effect is known as the SZ effect, and the distortion of the CMB spectrum that it causes can be measured, giving us a tool to probe dense clusters of galaxies. Hence, we can constrain the signals of modified gravity by looking at its predicted SZ power spectrums. In this thesis we consider a particular class of modified gravity models called the f(R) models. We use the popular Hu-Sawicki parameterization to describe our f(R) model. We look at the modifications made by this gravity to the halo model, specifically the halo mass function, which describes the distribution of halos by mass and redshift in our universe. We use this modified halo model to compute the 1-halo and 2-halo terms of the thermal-SZ power spectrum. By comparing it to the power spectrum in GR gravity, we are able to constrain the parameters of the f(R) model, and provide forecasts to measure the f(R) signal in future experiments.
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