An effective model for inflation from geometrothermodynamics: a detailed analysis of thermodynamics and cosmological perturbations

Inflationary models usually assume the existence of scalar fields or other exotic gravitational sources. We investigate an alternative approach in which the entire Universe is considered as a thermodynamic system described by geometrothermodynamics. A particular van der Waals like fundamental equation is used to construct an effective inflationary model which is consistent with the main physical requirements, such as the number of e-foldings and the times for the onset and end of inflation, predicting in this way a volume of approximately $10^{-84}$ m$^3$ at the onset of inflation. The phase transition structure and thermodynamic behavior of the system are consistent with the expected properties of an inflationary scenario. Cosmological perturbations of the model are shown to be in agreement with the corresponding primordial power spectrum providing the seeds for the creation of large-scale structure.