Enhancing the analysis of the large-scale structure of the Universe for cutting-edge cosmological surveys with two-point correlation function and beyond

Abstract

For many years, we have known that the Universe is vast and expands with acceleration on the largest scales. However, dark energy, the substance supposedly driving this acceleration, might also weaken with time. Or at least the current standard model of cosmology has a problem explaining all the highest-quality data available. We present one of the key technical ingredients that enabled the Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillation (BAO) distance measurements — the semi-analytic covariance matrices for the two-point correlation functions of point tracers. We then briefly discuss the cosmological implications of DESI BAO results, including the suggestion of dark energy. Then, we discuss a curious possibility of relieving the Hubble tension, the discrepancy in the expansion rate of the Universe today obtained directly from a Hubble diagram versus inferred indirectly from the CMB, without introducing fundamentally new physics. In the end, we explore a novel analysis technique combining galaxy redshift surveys with the data from the thermal Sunyaev-Zeldovich effect, a secondary anisotropy in the CMB. We aim to interpretably extract more valuable cosmological information from both than standard 2-point summary statistics allow. This would enable better consistency tests for the concordance model of cosmology and potentially new, exciting discoveries.