The cumulant generating function as a novel observable to cumulate weak lensing information

Key non-Gaussian properties of cosmological fields can be captured by their one-point statistics, providing a complement to two-point statistical measurements from power spectra or correlation functions. Large deviation theory can robustly predict the one-point statistics of cosmological density fields on mildly non-linear scales from first principles. It provides a direct prediction for the cumulant generating function (CGF) of such fields, from which a prediction for the more commonly used probability density function (PDF) is extracted through an inverse Laplace transform. For joint one-point statistics of multiple fields, the inverse Laplace transform rapidly becomes more cumbersome and computationally expensive. In this work, we demonstrate for the first time that the CGF itself can be used as an observable that captures an equal amount of cosmological information to the PDF. We use the weak-lensing convergence field as an example but in practice this result should be generally applicable for a multi-scale tomographic analysis of weak lensing and galaxy clustering.