Analytical and EZmock covariance validation for the DESI 2024 results

Understand

The estimation of uncertainties in cosmological parameters is an important challenge in Large-Scale-Structure (LSS) analyses.

• For standard analyses such as Baryon Acoustic Oscillations (BAO) and Full Shape, two approaches are usually considered.
• First: analytical estimates of the covariance matrix use Gaussian approximations and (nonlinear) clustering measurements to estimate the matrix, which allows a relatively fast and computationally cheap way to generate matrices that adapt to an arbitrary clustering measurement.
• On the other hand, sample covariances are an empirical estimate of the matrix based on en ensemble of clustering measurements from fast and approximate simulations.