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Effective Field Theory in Cosmology

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If you have a question about this talk, please contact Dr Joan Camps.

The recent tremendous progress in Observational Cosmology makes it now sensitive to non-linear corrections in the evolution of the density perturbations during the early epochs of the universe. In this context, the effective field theory paradigm represents the ideal setup to explore and systematically study the signatures that come from interactions, and additionally to directly map what we are learning from data into theory. I will describe two recent applications of this paradigm to Cosmology: the Effective Field Theory of Inflation and the Effective Field Theory of Cosmological Large Scale Structures (EFTofLSS). The first example represents the general parametrization of adiabatic fluctuations around an inflationary solutions, and it allows us to study the non-Gaussian signatures of Inflation, that I will describe. The second example is in the context of the gravitational clustering of dark matter. In our universe matter perturbations are large on short distances and small on large distances: strongly coupled in the UV and weakly coupled in the IR. We formulate an effective description based on an IR fluid-like system that allows us to formulate a manifestly convergent perturbative expansion to describe weak dark matter clustering. I will present the predictions of the EFTofLSS up to 2-loops. We find that it matches to percent accuracy the non-linear matter power spectrum up to k\sim 0.6 h/Mpc, requiring just one unknown coupling constant that needs to be fit to observations. Given that former perturbative techniques stop converging at k\sim 0.1 h/Mpc, our results demonstrate the possibility of accessing a factor of order 200 more dark matter quasi-linear modes than naively expected. If the remaining observational challenges to accessing these modes can be addressed with similar success, our results show that there is tremendous potential for large scale structure surveys to explore the primordial universe.

This talk is part of the Theoretical Physics Colloquium series.

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