Cosmic Covariance Matrices from (Mostly) First Principles

Counts-in-cells contain cosmological information complementary to that in the power spectrum, but calculating their covariance matrix requires knowledge of the correlation functions at each count level. On linear scales we characterize these “indicator correlations” given two simple assumptions; we also find that we can extend the characterization to non-linear scales using a simple fit. The result is an essentially first-principles recipe for the counts-in-cells covariance matrix.