Challenges to the standard cosmological model in recent cosmological observations

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The standard model of cosmology, the ΛCDM, has proven to be extremely effective in describing the dynamics of our universe. It assumes the presence of a fundamentalconstant in Einstein’s field equations, Λ , behaving as a uniformly-distributed and constant-in-time vacuum energy density, which dominates the current energy budget of our cosmos.Although the cosmological constant works quite well at the phenomenological level, it is also the origin of some important theoretical conundrums, as the old cosmological constant or the coincidence problems. Moreover, in the last years, the amazing improvement of the technological facilities at our disposal have allowed to detect some tensions within the ΛCDM. They affect e.g. the Hubble parameter H0 and σ8 , i.e. the root mean square of mass fluctuations at scales of 8 h^{−1} Mpc. Cumulatively, the tension with ΛCDM is at more than 3σ level: this represents therefore a great challenge to standard cosmology. In a few years, the tensions could be resolved or lead to a breakthrough in our understanding. This forces us to consider new theoretical landscapes.This project consists in exploring the phenomenological viability of such landscapes,mainly those involving dynamical vacuum and dark energy models which have already proven in previous investigations to be capable of loosening some of the aforesaid tensions. The analysis will include a study of massive neutrinos and their potential degeneracy with the dynamical dark energy components, together with the possible connection between the inflationary and the current speeding-up phases of our universe.This project is meant to support A. Gómez-Valent with a post-doc fellowship for two years.He has been one of the first to point out the combined effect of the tensions with the concordance cosmology and has a strong know-how in analyzing several complementary cosmological datasets. I already published a paper with him and I am therefore confident he is the right person to carry this project to successful completion.