Dark energy (DE) is believed to be the physical cause that produces the measured accelerated expansion of the universe. Within the standard model of cosmology (i.e. the current paradigm) the DE is identified with a strict cosmological constant. However, the plain simplicity of this idea lies at the root of its unconvincing theoretical status. In addition, phenomenologically, the standard model is also disputable at present. Tensions of various sorts and of different degrees are known to be present among existing datasets within such framework. For example, the recently measured local value of the Hubble parameter, H0, is significantly higher than the one inferred from the measurements of the anisotropies in the cosmic microwave background (CMB) by the Planck satellite. Also, the current paradigm predicts exceeding structure formation power as compared to the observations etc. The possibility that these facts are actually pointing to serious 'cracks' in the current cosmological paradigm is slowly but strongly setting in.
In this work, the student will have the opportunity to explore the nature of these cosmological problems as well as some theoretical models of dynamical DE capable to alleviate them. Among these models, the dynamical vacuum models are well-motivated from the theoretical point of view (e.g. within quantum field theory in curved spacetime). Interestingly, they also predict a possible time variation of the fundamental "constants" of Nature, including the masses and couplings of the elementary particles, what could act as an additional signature of physics beyond the standard models both of particle physics and cosmology.