| dc.description.abstract | Inflation is a theory that provides an attractive explanation for the early evolution of our universe, producing a large, spatially flat and really homogeneous observable universe. At the same time, it explains how inflation may be a source for the small primordial perturbations that we observe in the sky and are the origin of large-scale structures today.
Initially it was considered that only one scalar field would be enough to describe inflation but in recent years we have learnt from string theory that one could expect to find more than one scalar field that could play a role in inflation, opening a wider scenario for this theory. The conditions we need to ask to the scalar field in the case of having a single one are clear, but these are not so evident in multi-field case. At the same time, we know how potentials must be in single-field in order to satisfy these conditions, but again, it is far from clear what potentials must be ruled out of the multi-field case.
Here we derive the correct conditions for multi-field inflation and which potentials can be used in such a case. Usually people only consider the case where the field follows the gradient of the potential, because they use conditions analogous to the single-field ones, but with the conditions derived here we can argue that multi-field inflation is more general than that, as, for instance, trajectories perpendicular to the gradient of the potential seem to fulfil the necessary conditions to get an inflationary epoch in our universe. An stable model with such a trajectory is shown at the end of this thesis. | |
