L. Amendola, M. Kunz, M. Motta, I. Saltas, I. Sawicki
The aim of this letter is to answer the following two questions: (1) Supposing we had infinitely precise cosmological observations of the expansion history and linear perturbations in a range of redshifts and scales, which properties of the dark energy could actually be reconstructed without imposing any parametrization? (2) Are these observables sufficient to rule out not just a particular dark energy model, but the entire general class of viable models comprising a single scalar field? This paper bears both good and bad news. On one hand, we find that the goal of reconstructing dark energy models is fundamentally limited by the unobservability of the present values of the matter density $\Omega_{m0}$, the perturbation normalization $\sigma_{8}$ as well as the present matter power spectrum. On the other, we find that, under certain conditions, cosmological observations can nonetheless rule out the entire class of the most general single scalar-field models, i.e. those based on the Horndeski Lagrangian.
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http://arxiv.org/abs/1210.0439
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