Evolution of Perturbations in a Domain Wall Cosmology

A fluid of domain walls may have an effective equation of state pw = − 23ρw. This equation of state is qualitatively in agreement with the supernova type Ia observations. We exploit a cosmological model where the matter content is given by a dust fluid and a domain wall fluid. The process of formation of galaxies is essentially preserved. On the other hand, the behaviour of the density contrast in the ordinary fluid is highly altered when domain walls begin to dominate the matter content of the Universe. This domain wall phase occurs at relative recent era, and its possible consequences are discussed, specially concerning the Sachs-Wolfe effect. One of the most surprising observational results in cos-mology in the end of this century is due to the use of the Supernova type Ia as standard candles in the evaluation of luminosity distance as function of the redshift z. The two groups consecrated to this program [1, 2] arrived at the same conclusion: the Universe is now in an accelerated phase. The inflationary paradigm, initially restricted to the very early Universe, was transferred to the Universe today with strinking consequences, for example, for the age of the Uni