The acceleration of the universe and the physics behind it

Abstract

Using a general classification of dark enegy models in four classes, we discuss the complementarity of cosmological observations to tackle down the physics beyond the acceleration of our universe. We discuss the tests distinguishing the four classes and then focus on the dynamics of the perturbations in the Newtonian regime. We also exhibit explicitely models that have identical predictions for a subset of observations.

Testing general relativity: from local to cosmological scales

“…Among these tests, it has been shown that general relativity can be tested by using observations of the large-scale structure of the universe [1,6], as first proposed by Uzan & Bernardeau [7] ten years ago or by studying the fundamental constants [8][9][10][11]. We shall discuss them below.…”

“…In the last class (lower left, class B), the distance duality relation may be violated. Adapted from Uzan [6]. (b) The regimes in which one may modify general relativity and the related systems that can be used to constrain these modifications.…”

Tests of general relativity on astrophysical scales

“…This lies in the fact that the only quantity at hand is H(z) and most of the models of the literature can be tuned to reproduce the same function (see Ref. [56] for explicit examples). No null test of GR can be constructed with background data since they all are functions of H(z).…”

“…This idea to construct such a post-ΛCDM parameterisation on sub-Hubble scales was first proposed in Ref. [56], following the analysis of the particular case of scalar-tensor theory by Ref. [27].…”

“…We thus have two possibilities. Either one compute explicitely these terms in some classes of theories such as f (R), DGP or scalar-tensor [56,67,68] or one specifies some ansätze for these functions, in the same spirit as we introduced the parameterisation (9) for the dark energy equation of state.…”