Scalar fields in Cosmology: dark matter and inflation

Scalar fields have been widely used in cosmology during the last three decades, but it is until now that we have been able to fully understand their role as possible major matter components for the evolution of the Universe. Here we briefly present recent studies on scalar fields that show how their intrinsic properties are translated into observables related to the process of structure formation. In the first case, we consider a massive scalar field as a dark matter component, and present the corresponding mass power spectrum. It is confirmed that one of the distinctive features of the model is the suppression of structure at small cosmological scales. In the second case, we describe a generic method to find inflationary solutions without the need to be specific about the scalar potential. The method shows that single-field models of inflation can be classified in two groups according to their predictions of inflationary observables.