Cosmological models with running parameters

Resumo

This thesis is devoted to the study of cosmological models in which both the cosmological 'constant' and the gravitational coupling G may be evolving (running) quantities, their dynamics stemming from the quantum effects of massive fields. In some of those models, other contributions to the dark energy (apart from the cosmological term) may also be present, in the form of a generic component X. Such a composite nature of the dark energy fluid may have interesting consequences, providing for instance a possible explanation for the cosmological coincidence problem. The theoretical foundations and phenomenology of this kind of models, as well as their impact on the late growth of structure, are addressed in detail in the thesis. The requirement that several observational bounds are satisfied by the models results into stringent constraints over their free parameters. At the end of the day, we will have presented a series of theoretically well-motivated models, with interesting physical implications and also some distinctive features that could be detected in the present and next generation of high precision experiments. Those probes will certainly provide an insight into the fundamental problems of Cosmology, like the nature of dark energy. We cannot foresee what they will bring to light, but the models with running parameters presented in this thesis remain as appealing and viable candidates to account for the dark energy of the Universe.