Precision Cosmology With Galaxy Surveys

This thesis is dedicated to the design and development of efficient and robust precision tools to analyze the cosmological large-scale structure(LSS).I will present how I applied a perturbative approach describing gravitational clustering in the mildly nonlinear regime,called the Effective Field Theory of Large-Scale Structure(EFTofLSS),to LSS data,in order to extract reliable cosmological information.In particular,I will focus on the analyses of the Baryon Oscillation Spectroscopic Survey(BOSS)data from the EFTofLSS that I carried.First,I will show how I was able to measure all parameters of the standard model,ΛCDM,from LSS data only,at a precision rivaling other cosmological probes.Importantly,these constraints from the LSS,that I obtained independently from the cosmic microwave background(CMB)anisotropies or the cosmic distance ladder(CDL),are consistent with the measurements from the CMB.I will put special emphasis on the efficiency of the analysis tools I built to that end,and on the tests I conducted to assert the reliability of the methods.Second,I will present cosmological explorations I made beyond ΛCDM,that were enabled by this technology.Focusing on late-time acceleration,I will show that cosmological data,together with strong physical priors imposed by quantum field theory,restrict deviation from a cosmological constant within a limited range.As another illustration of the analysis methods that I developed,I will also discuss the Hubble tension between the CMB and the CDL in light of LSS data.I will show how the BOSS data together with the EFTofLSS break the degeneracy between the Hubble constant and the sound horizon at decoupling introduced by early dark energy models,that were designed to uplift the value seen in the CMB,making them less opportune to reduce the tension.Third,I will present how I analyzed the BOSS data from the EFTofLSS in configuration space,in contrast to the previous analyses that I performed in Fourier space.Indeed,It is not completely equivalent in terms of information and measurement systematics.Consistency between the two results highlights the robustness of the cosmological measurements.Finally,I will scrutiny the time dependence of the LSS observables,which are usually computed at a single,approximate,effective redshift.Precisely,I will show how to go beyond this approximation,by computing the LSS observables with exact-time dependence.I will argue that for future large-volume surveys,exact-time evaluation might be necessary to get unbiased cosmological constraints.Besides the cosmological results presented here,the work reported in this thesis enables efficient and reliable cosmological explorations in the next stage of LSS surveys.