Thesis

Light Paths in Inhomogeneous Universes and the Late Acceleration of the Universe

• Call:

  IDPASC Portugal - PHD Programme 2015

• Academic Year:

  2015 / 2016

• Domains:

  Cosmology | Astrophysics

• Supervisor:

  José Pedro Mimoso

• Co-Supervisor:

  Antonio da Silva

• Institution:

  Faculdade de Ciências - Universidade de Lisboa

• Host Institution:

  Instituto de Astrofísica e Ciencias do Espaço

• Abstract:

  The standard cosmological model is extremely successful in providing an explanation for the major observational features of the Universe. The fundamental milestone of the model is the so-called cosmological principle that assumes that the space-time is homogeneous and isotropic. This hypothesis was strongly supported by the discovery of the Cosmic Background Radiation in 1965. It has further been strengthened by the recent detailed observations of this radiation (for instance by the WMAP, and Planck satellites) that test the isotropy at large scales, beyond the Gpc. However at intermediate scales the observed Universe is inhomogeneous, as witnessed by a variety of structures such as galaxies, clusters of galaxies, voids, and extremely compact objects that we cannot directly see, such as black holes… The recent discovery of an unexpected acceleration of the Universe at z ~ 0,5-1 as led to the investigation of different explanations for the underlying repulsive effect. Among these explanations one possibility that has been envisaged relies on the gravitational role played by inhomogeneities, such as the effect of a large local void. In order to fully ascertain the implications of inhomogeneities on the observed late inflationary stage, we propose to analyze in full detail the observational signatures of the deviations from isotropy at intermediate scales. This require us to consider inhomogeneous general models and investigate the trajectories of light paths and its implicit observational features within these models: redshifts, horizons, lensing effects, integrated Sachs-Wolfe effect. This is the purpose of the present research work, where a combination of theoretical tools with observational data from Planck and other empirical sources will be put explored. The underlying goals of the project relate to the goals of the Euclid ESA mission.