Impacto de extensões da gravidade na inflação e reaquecimento

Abstract

In this work, we investigate the impact of extensions of gravity in cosmic inflationary scenarios, in which a scalar field, dubbed inflaton is considered as responsible for the accelerated expansion of the primordial Universe. In particular, we will see how such changes affect the cosmic microwave background radiation temperature power spectrum, determined with great precision by the most recent experiments that investigate it. Initially, we consider that the inflaton is non-minimally coupled to gravity, and we will check the predictions for two specific models. The first one is characterized by the β-exponential potential, which generalizes the well-known power-law inflation, and it is motivated by brane dynamics; the next model arises from a supergravity realization, usually called the Witten-O’Raifeartaigh inflation. Through a statistical analysis, we will establish constraints on cosmological parameters of the specific models, determining if there is any preference from data for the presence of a nonminimal coupling. The connection of such models with the reheating period is investigated next, in a way that we seek to establish the relation between the duration and temperature of reheating with the properties of the model. By choosing the Witten-O’Raifeartaigh one, we use the results of the previous analysis to numerically model the post-inflationary era, in a way that non-linear effects on the growth of perturbations of the field are considered, resulting in an amplification of said fluctuations through a preheating process. These fluctuations can be responsible for the formation of long-lived structures dubbed oscillons, argued as a possible source of primordial gravitational waves. Finally, we check the possibility of application of the β-exponential scenario to the warm inflation picture, in which the energy dissipation of the field into radiation is realized at the same time that inflation proceeds, with the degree of dissipation greatly impacting the predictions of a given model. We will see that for the β-exponential model, it is possible to make the strong dissipation regime concordant with the swampland conditions, recently investigated in the literature in the context of warm inflation.