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PROYECTO FONDECYT 1051086 TITULO: POSSIBLE MATTER SOURCES OF THE UNIVERSE. Investigador Principal Mauricio Cataldo Monsalves Facultad/Depto. Ciencias/Física E-Mail [email protected] Coinvestigadores Sergio del Campo A. (P.U.C.V.) Patricio Salgado A. (U. de C.) OBJETIVOS: - The general goal is to study a wide range of cosmological models for the Universe, which might describe either early or the present stage of the Universe during its expansion. The possibility of an anisotropic state at early times in the evolution of the Universe is a very natural idea to explore. These anisotropies could have many possible sources. RESUMEN Y RESULTADOS: In this proposal we want to study a wide range of cosmological models for the Universe, which might describe either early or the present stage of the Universe during its expansion. One of the key problems of the current cosmology is deciding which kind of matter sources are present in the Universe. This means that there is a notable uncertainty about the presence or absence of matter fields, which might contribute to the total energy density today. At the early stage the kind of matter fields is even more uncertain. One of main points of this research is to investigate the consequences of the existence of an inflationary era for the evolution of the early Universe, taking into account dissipative processes described by a viscous cosmic fluid. The early expansion stage may be described by isotropic or anisotropic line elements (for instance, such as Friedmann-RobertsonWalker or Kasner type metrics respectively). Imperfect cosmic fluid is a suitable source for anisotropic Universe models. In this case the matter content may be a viscous (or nonviscous) fluid, a magnetic and an electric field (liner or nonlinear electrodynamics), scalar fields, long wavelength gravitational waves, Yang-Mills fields, axion fields in low energy string theory and different kind of topological defects, such that cosmic strings, domain walls, among others. The present expansion stage of the Universe is accelerating. On the one hand this acceleration has been associated with the presence of a cosmological constant, but on the other hand this acceleration may be explained by the so called “quintessence” models. With respect to the present scenarios we shall consider cosmological models described byisotropic or anisotropic metrics, with perfect or imperfect fluids together with a quintessence-type scalar field. A possible relation between the homogeneity of the Universe and the dimensionality of space will also be treated. All considered models for the early Universe must give the necessary initial conditions for the formation of the large scale structure observed in the Universe today. On the other hand, the cosmological models must be compatible with the strong energy condition and with the second law of the thermodynamics, so that a generation of entropy in viscous models could be appropriately described. Perturbations around a background solution allow us to determine explicit expressions for the contrast energy-density /, together with the power spectrum P(K) with inflationary initial conditions. These expressions will be confronted with related astronomical observations (such that the observational data obtained by recently completed BOOMERANG and MAXIMA experiments and by the second generation satellite experiments such that WMAO and PLANCK), so that the specific parameters that enter in our models could be determined.