“…Estimation of correlation matrices is among the most fundamental statistical tasks, basic to standard methods and widely used in applications. Modern examples include viral sequence analysis and vaccine design in biology (Dahirel et al, 2011;Quadeer et al, 2014Quadeer et al, , 2018, large portfolio design in finance (Plerou et al, 2002), signal detection in radio astronomy (Leshem and van der Veen, 2001), and collaborative filtering (Liu et al, 2014;Ruan et al, 2016), among many others. In classical statistical settings, with a limited number of variables p and a large sample size n, the sample correlation matrix performs well.…”