Cosmology with interaction in the dark sector of the Universe

According to our understanding of the universe, dark matter and dark energy are the dominant components in the dynamics of the current universe, while baryons and radiation contribute only a small fraction of less than 5% of the cosmic energy. Although this dark sector is important to describe a series of phenomena that are currently observed, its nature is still one of the greatest mysteries of cosmology. In this work we consider the study of models that, unlike the standard model, present a non-gravitational interaction between dark matter and dark energy. Initially, this interaction is written in terms of an arbitrary function of the ratio between the energy densities of dark matter and dark energy. In the background level it is presented a model-independent way to reconstruct the interaction directly from the data. Afterward, some specific models are chosen to be tested using the most recent cosmological data via a suitable modified version of the Boltzmann code CLASS and the statistical code MontePython. The main purpose of this analysis is to verify if any set of observational data indicate some interaction in the dark sector in counterpart of the $\Lambda$CDM model, and if there is a concordance between the background results and the results at the linear level.