According to the current consensus cosmological model, dark matter and dark energy make up most of the energy density of the universe. However, their physical nature is still unknown and understanding them presents a grand challenge. Moreover, there are unresolved tensions between observations from the late-time and the early-time universe. Intriguingly, most weak lensing analyses favour a smoother matter distribution than Planck's Cosmic Microwave Background observations. In order to assess if this discrepancy is due to unaccounted systematics or new physics, it is essential to analyse the existing weak lensing datasets with a unified pipeline. This effort is especially required as we approach the next generation of dark energy surveys —including ESA's Euclid mission, the Vera C. Rubin Observatory Legacy Survey of Space and Time, and the Nancy Grace Roman Space Telescope— since they will provide unprecedented high-quality data that will increase the statistical power by orders of magnitude.
In this project, we aimed to combine for the first time the final data sets from the current generation of dark energy surveys (DES, KiDS and HSC) to obtain competitive cosmological constraints from the joint analysis of galaxy clustering and weak lensing. For this purpose, we have worked on developing a novel unified modelling and inference pipeline to fully exploit the statistical power of the different surveys in an optimal way. The methodology developed and employed in this project will be crucial to shed light on the existing tensions with Planck and the nature of dark energy with ESA's Euclid mission, the Rubin Observatory and the other upcoming dark energy surveys.
