http://arxiv.org/abs/1612.00752
In many astrophysical settings covariance matrices of large datasets have to be determined empirically from a finite number of mock realisations. The resulting noise degrades inference and precludes it completely if there are fewer realisations than data points. This work applies a recently proposed non-linear shrinkage estimator of covariance to a realistic example from large-scale structure cosmology. After optimising its performance for the usage in likelihood expressions, the shrinkage estimator yields subdominant bias and variance comparable to that of the standard estimator with a factor $\sim 50$ less realisations. This is achieved without any prior information on the properties of the data or the structure of the covariance matrix, at negligible computational cost.
B. Joachimi
Mon, 5 Dec 16
46/61
Comments: 5 pages, 5 figures; accepted for publication in MNRAS