Constraining modified gravity with cosmic voids

Author(s)

Rodrigo Voivodic

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2021-09-21

Examining board members

Marcos Vinicius Borges Teixeira Lima; Eduardo Serra Cypriano; Rogério Rosenfeld

• Advisor: Marcos Vinicius Borges Teixeira Lima

Abstract

In this work, we investigated observables related to the large-scale structure of the Universe, especially those sensitive to gravitational effects, and can be used to constrain gravity theories. Our main goal was the study of cosmological voids, both the development of codes for detecting them in N-body simulation and observations, as well as the construction of theoretical predictions for these observables as functions of cosmological and gravity parameters. Given these measurements and theoretical predictions, we studied the constraining power of voids, in comparison with other observables, and we assessed the effects of observational complications. We constructed algorithms to find halos and voids, using a Voronoi tessellation, as well as codes to measure the power spectrum and the bispectrum of a catalogue of voids, halos, and matter. We also produced codes to measure the density and velocity profiles of halos and voids, and we proposed a new theoretical prediction for the void abundance in f(R) and Symmetron models of modified gravity. These tools allowed us to put constraints on modified gravity parameters using void abundance. We also developed a generalization of the standard Halo model to include the effects of cosmic voids, in the so-called Halo-Void model. In addition, we computed the turnaround radius of halos in f(R) gravity and related the theoretical computations with current observations. Finally, we constructed a new method for the fast generation of halo catalogues, which are crucial for the computation of covariance matrices in next-generation galaxy surveys. (AU)

• FAPESP's process: 16/19647-2 - Constraining modified gravity theories with void properties
• Grantee: Rodrigo Voivodic
• Support Opportunities: Scholarships in Brazil - Doctorate