COSMOLOGICAL OBSERVATIONS AND BACKREACTION

Since the very beginning the Friedmann-Robertson-Walker metric has played one of the most important roles in developing cosmology. The underlying assumptions of maximal symmetry have simplified our general view of the Universe but recent developments in observational cosmology, like the discovery of cosmic acceleration, have demonstrated that a more precise approach is required. Dealing with the inhomogeneities of the matter distribution in the Universe has led to the problem of defining averages in a relativistic framework. After having reviewed the basics of the Standard Model, we introduce the longstanding problem of averaging in relativistic cosmology and the cosmological backreaction in the formulation proposed by Buchert. We follow the suggestion of probing backreaction against data applying the method based on a template friedmaniann-like metric developed by Larena et al. in 2008. We test the backreaction model against SN data of the Union2.1 release, clusters and CMB measurements from Planck and WMAP-9yr using different sets of observables. We find that the improvements in SN and cluster data confirm Larena's results providing slightly better constraints. Unfortunately current CMB data shed light on underlying approximations in matching the backreaction model and standard CMB theory, showing that the derived constraints on cosmological parameters are in contrast with predictions from the other data sets and consequently we have to handle them with care.