Improving the precision matrix for precision cosmology
  The estimation of cosmological constraints from observations of the large
scale structure of the Universe, such as the power spectrum or the correlation
function, requires the knowledge of the inverse of the associated covariance
matrix, namely the precision matrix, $\mathbf{\Psi}$. In most analyses,
$\mathbf{\Psi}$ is estimated from a limited set of mock catalogues. Depending
on how many mocks are used, this estimation has an associated error which must
be propagated into the final cosmological constraints. For future surveys such
as Euclid and DESI, the control of this additional uncertainty requires a
prohibitively large number of mock catalogues. In this work we test a novel
technique for the estimation of the precision matrix, the covariance tapering
method, in the context of baryon acoustic oscillation measurements. Even though
this technique was originally devised as a way to speed up maximum likelihood
estimations, our results show that it also reduces the impact of noisy
precision matrix estimates on the derived confidence intervals, without
introducing biases on the target parameters. The application of this technique
can help future surveys to reach their true constraining power using a
significantly smaller number of mock catalogues.
