COSMOBEST · COSMOlogy BEyond Standard Techniques: a program to exploit cosmic voids for precision cosmology

Cosmology addresses the fundamental questions about our Universe: what is it made of? how does it evolve? Observations suggest that the Universe is undergoing an accelerated expansion---to explain it, cosmologists hypothesize the existence of a mysterious component: dark energy. Despite major recent advances in the field, up to now traditional methods in cosmological analysis have failed to provide a throughout understanding of dark energy. Large-scale surveys, mapping the distribution of billions of galaxies in the Universe, allow us to look back in time and encompass the era when dark energy rises: they are a powerful tool to address our fundamental questions. The next generation of surveys, and in particular the ESA Euclid mission, will map the Universe with high-quality measurements reaching unprecedented precision; they will sample the galaxy distribution in detail also in the emptier regions with fewer galaxies: voids. Void cosmology is in its golden age, and constitutes nowadays an increasingly active sector of galaxy clustering analysis: by measuring void properties we obtain stringent constraints on cosmological parameters. Voids allow to perform a novel and independent analysis of large-scale structure data, bringing us in the regime of COSMOlogy BEyond Standard Techniques. Voids are extremely sensitive to the properties of dark energy and neutrinos, and are a powerful tool to test general relativity in a new regime. COSMOBEST is an ambitious ERC program aiming to exploit voids as a novel and robust tool to shed light on the puzzles of modern cosmology. It capitalizes on the PI's wide experience in building void science in large collaborations, with a strong focus on calibration-free techniques and systematics control. With COSMOBEST I will lead void analysis from modern data, guaranteeing for Europe a worldwide leadership in delivering constraints on dark energy, neutrinos and general relativity from the next generation of surveys.