The last decades have seen a fantastic and steady improvement in our understanding of the early Universe, culminating with the recent release of the Planck data. Despite its marvelous accomplishments, a somewhat common sentiment in the community is that Planck results have ruled out 'exotic' models for the production of primordial density fluctuations, and the current bounds on Non-Gaussianities 'strongly favor' simple models. However, both these statements lack a robust (model-independent) support. In this talk I review a bottom up approach to Cosmology
led by an Effective Field Theory (EFT) formalism, which has proven to be very successful in Particle Physics, where model independent questions may be addressed.
For instance, quantum fluctuations in vacuum appear as a natural candidate to produce the observed (scale invariant) power spectrum, but how do we systematically search for departures of this picture?
Is the theory of density perturbations strongly coupled at some high(er) scale, or is single field slow roll inflation the `Higgs mechanism' of Cosmology?
Measurements of the CMB are limited by several effects, which requires searching for new venues in order to improve our current bounds. Large Scale Structure (LSS) surveys, on the other hand, appear as a natural candidate to become the next leading probe for precision Cosmology. In the last part of my talk I discuss the (Lagrangian) EFT approach to LSS (LEFT, constructed borrowing ideas from the EFT for gravitational wave emission in binary black holes) which parameterizes the information from the non-linear dynamics in a systematic fashion, thus increasing the number of modes amenable to a perturbative treatment. This is an essential step towards improving Non-Gaussiantity bounds, and ultimately addressing fundamental questions about the physics of the early universe, all within the framework of EFT.
