The precise determination of cosmological parameters, including the properties of dark energy, are at the heart of the Planck and Euclid space missions. They are also those of major ground-based telescope survey projects with very similar methodological approaches: DES, Vera Rubin, DESI, and ACT, SPT, S4 for the CMB. It is quite clear that the ultimate constraints will be obtained by the joint use of data sets from these different experiments. However, this objective requires a complex step: these data sets are indeed from partially overlapping sky areas. This requires on the one hand to take into account the effect of redundancy of data from different instruments, thus whose selection effects are radically different, an advantage to identify spurious systematics errors, but also, on the other hand, to take into account the fact that the overlap of these data brings additional information through their cross-correlation, an essential contribution as demonstrated in the Euclid consortium. The joint use of these data therefore requires the development of appropriate methods, which is the case for the joint use of future Euclid data with Planck data, but which has not yet been fully taken into account for the joint use with other data that are already available or that will be available in the next few years or even months.
The international research network (IRN) CCD2030 is devoted to this purpose. It is sponsored by the CNRS-INSU and by the GdR CoPhy.
Invited speakers: Eric Armengaud, Marc Bétoule, Boris Bolliet, Julien Carron, Giulio Fabbian, Julien Lesgourgues, Anna Porredon, Emmanuel Schaan, Blake Sherwin, Isaac Tutusaus, Tianyi Yang
