Cosmology at a Crossroads: clarifying tensions between cosmic microwave background, cosmic shear and galaxy clusters data.
With new methods and technology, the accuracy in cosmological measurements has vastly improved in the past years. The recent observations of the Cosmic Microwave Background Anisotropies from the Planck satellite experiment, for example, have spectacularly confirmed the expectations of the standard cosmological model. This is of crucial importance since this model is based on three assumptions that require new physics beyond the standard model of particles: dark matter, a cosmological constant and inflation. However few but interesting tensions between cosmological datasets are emerging that clearly deserve further investigations since could reveal new properties of this new physics sector. For example, the cosmic microwave background data seems to predict a value of the cold matter density background and perturbations that is larger than the one directly measured by cosmic shear surveys and galaxy clusters number counts. This tension is currently above the two standard deviations and future datasets can play a key role in confirming or falsifying it.
Moreover the current determination of the Hubble constant based on luminosity distances from Riess et al. 2018 is about 3.8 sigma away from the determination based on Planck data under the assumption of the standard cosmological model.
Again, a combined analysis of GC and CS data could provide new constraints on the Hubble constant and confirm or rule out the present tension. In this proposal we aim to study in detail those tensions and anomalies by identifying possible systematics and investigating at the same time possible extensions to the standard model that could explain them. We will focus on three main cosmological observables: Cosmic Microwave Background (CMB) anisotropies, Cosmic Shear (CS) and Galaxy Clusters (GC).