Scientific Seminars
How big is the Universe?
Roberto Trotta
Imperial College, London, UK
2009-05-20 14:00 Brera - Cupola Fiore
The question of determining the spatial geometry of the Universe is of greater relevance than ever, as precision cosmology promises to verify inflationary predictions about the curvature of the Universe. A determination of the geometry of the Universe (which can be either flat, closed or open) would also allow to measure its size, which is finite only in the case of a closed Universe. In this talk I will revisit the question of what can be learnt about the spatial geometry of the Universe from the perspective of a three-way Bayesian model comparison. After reviewing the status of current cosmological data sets, I will discuss how we can compute the probability that the Universe is spatially infinite, and present results from a compilation of observational data. I will also discuss the future prospects for improving on current bounds, arguing that the geometry of the Universe is not knowable if the value of the curvature parameter is below |Omega_curvature| ~ 10^{-4}, a bound one order of magnitude larger than the size of curvature perturbations, ~ 10^{-5}. |