Objective Astronomy is grappling with a profound issue: the origin of the accelerated expansion of the universe. Is it caused by a mysterious dark energy, or a new aspect of the gravitational interaction? Galaxy clusters, the largest structures in the Universe, will help answer this question. Cluster formation and evolution are driven by the evolution of the universe itself and cluster abundance is therefore a powerful observational tool that tightly constrains the cosmological model, such as dark energy, and key quantities of fundamental Physics, such as modifications to gravitational theory. These constraints complement and strengthen those from other observational probes, such as type Ia supernova (SNIa), gravitational lensing and baryon acoustic oscillations (BAO). Critical aspects in the scientific analysis of cluster surveys are the survey selection function, relating the survey catalogue to the general cluster population, and the relation between the observable richness and cluster mass, the basic theoretical quantity. The establishment of these two elements is critically needed for the exploitation of optical/near-infrared imaging cluster surveys planned by the European scientific community. We propose to fill this need by 1) quantifying imaging survey cluster selection functions and 2) determining the form of the cluster richness-mass relation using a synergy between observations and well-behaved realistic mock catalogues; we will then 3) introduce this information into the Fisher Matrix formalism to predict possible constraints on theoretical models, e.g the dark energy equation-of-state or modified gravity scenarios. The precision targeted by planned imaging surveys (e.g. Euclid, J-PAS, LSST, WFIRST) surpasses all previous analyses. Detailed evaluation of expected constraints under realistic conditions as proposed by our research lies at the forefront of current effort in field. Fields of science natural sciencesphysical sciencesastronomyastrophysicsdark matternatural sciencescomputer and information sciencesartificial intelligencemachine learningnatural sciencesphysical sciencesastronomystellar astronomysupernova Programme(s) H2020-EU.1.3. - EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions Main Programme H2020-EU.1.3.2. - Nurturing excellence by means of cross-border and cross-sector mobility Topic(s) MSCA-IF-2014-EF - Marie Skłodowska-Curie Individual Fellowships (IF-EF) Call for proposal H2020-MSCA-IF-2014 See other projects for this call Funding Scheme MSCA-IF-EF-ST - Standard EF Coordinator CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS Net EU contribution € 173 076,00 Address Rue michel ange 3 75794 Paris France See on map Region Ile-de-France Ile-de-France Paris Activity type Research Organisations Links Contact the organisation Opens in new window Website Opens in new window Participation in EU R&I programmes Opens in new window HORIZON collaboration network Opens in new window Other funding € 0,00