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Résumé |
The phase of accelerated expansion that the Universe is currently undergoing has had a extremely stimulating effect on theorists. We now have a plethora of models that could possibly explain why we measure a value of the cosmological constant that is non zero. Most of them provide a dynamical explanation for such a phenomenon, which in the simplest and most studied cases, is sourced by an extra scalar field. The modifications ensuing can in principle be quantitatively compared to current observations, that are now at a level accurate enough to be restrictive. In particular, future surveys like Euclid will be able to measure the behavior of Dark Energy beyond the simple homogenous quantities that we constrain today. This is why we need a way to connect efficiently,and almost algorithmically, the zoology of models to observations, in order to sort out those that survive the comparison with data. The idea behind the Effective Field Theory of Dark Energy is exactly that. This formalism is based on very general symmetry arguments, so that it can describe a wide range of models. I will show how most of them reduce to only a few functions of time, which in turn can be linked to observable quantities. More fundamentally, this approach allow oneself to see how restrictions that theorists demand on their models, mostly for stability, meet the constraints that observations will soon impose. |
