GRAVITATION

Author: Izquierdo Sáez Germán.
Year: 2005.
University: AUTÓNOMA DE BARCELONA [www.uab.es].
Place of defense: Facultat de Ciencias.
Place of preparation: Grupo de Fíca de la materia Condensada.

Summary: The primordial gravitational waves represent a unique window to determine the evolution of the Universe, because with its spectral serious possible to reconstruct the scale factor from the initial moments of expansion until this moment. In this thesis, working vacuum adiabatic approximation, we have revised the expansion of the universe amplifies fluctuations in the quantum vacuum. We have assessed the spectrum in a model of expansion of the universe that was considered an initial inflationary, an era dominated by primordial black holes and radiation, an era dominated by radiation and finally an era of the art. We have demonstrated how the specter of this scenario is much lower than the usual pattern (inflation was radiación-era matter), we have also seen how the observed anisotropies of CMB put limits on the parameters of the model free of the four eras. We have calculated the spectrum in a model with a universe dominated by dark energy in the present age, and concludes that although this spectrum coincides with the scene of the three eras evolves differently. We have also calculated the spectrum in a hypothetical second was from the area, in the event that this era of rapid expansion is only a transitional phase. We have studied plays as the second law of thermodynamics during the era of rapid expansion, with a entropy to the primordial gravitational waves that must meet a certain condition. Finally, setting aside the gravity waves, we have studied the second law of thermodynamics in universes dominated by dark energy ghost, concluding that the entropy of these fluids is negative and that the second law is respected.