The COSMOBEST project aims at fully exploiting the golden era of cosmic voids, the large underdense regions in the galaxy distribution, leveraging on the next generation of large-scale surveys. It will provide the best constraints on our Universe from the independent tool of voids, to be combined with more traditional methods. To reach such goal, it builds a framework for void science in the context of three important missions: the Dark Energy Spectroscopic Instrument (DESI), the ESA Euclid mission and the Rubin Observatory of the Legacy Survey of Space and Time.
Cosmic voids allow to perform a novel and independent analysis of large-scale structure data, bringing us in the regime of COSMOlogy BEyond Standard Techniques. They are extremely sensitive to the properties of dark energy and neutrinos, and are a powerful tool to test general relativity in a new regime. The first goal of the program is to build robust void catalogs from DESI and Euclid data, as well as prepare robust forecasts for Rubin voids. Void analysis needs to be paired with a deep understanding of systematic effects: in the era of precision cosmology it is fundamental to control systematics down to a sub-percent level—since better data brings statistical errors down. Modelling and understanding systematics is the most important challenge for modern cosmology, as we pin down the parameters describing our Universe. In this sense voids have the advantage of being regions where theoretical models perform better and where the control of systematics is easier. Since we have entered in the golden age for voids, void catalogs provide huge numbers of objects to measure void statistics. The study of systematics must be done for each statistic, the main ones being the void size function and the void-galaxy cross-correlation function. With COSMOBEST we aim at providing robust and tight cosmological constraints from voids, leveraging on the era of big large-scale structure data with DESI, Euclid and Rubin.
