PIRSA:13030110

The Effective Field Theory of Large Scale Structures

Pajer, E. (2013). The Effective Field Theory of Large Scale Structures. Perimeter Institute. https://pirsa.org/13030110

Pajer, Enrico. The Effective Field Theory of Large Scale Structures. Perimeter Institute, Mar. 19, 2013, https://pirsa.org/13030110 

          @misc{ pirsa_PIRSA:13030110,
            doi = {10.48660/13030110},
            url = {https://pirsa.org/13030110},
            author = {Pajer, Enrico},
            keywords = {Cosmology},
            language = {en},
            title = {The Effective Field Theory of Large Scale Structures},
            publisher = {Perimeter Institute},
            year = {2013},
            month = {mar},
            note = {PIRSA:13030110 see, \url{https://pirsa.org}}
          }

Enrico Pajer

Utrecht University

Talk number
PIRSA:13030110
Collection
Talk Type
Subject
Abstract
An analytical understanding of large-scale matter inhomogeneities is an important cornerstone of our cosmological model and helps us interpreting current and future data. The standard approach, namely Eulerian perturbation theory, is unsatisfactory for at least three reasons: there is no clear expansion parameter since the density contrast is not small everywhere; it does not consistently account for deviations at large scales from a perfect pressureless fluid induced by short-scale non-linearities; for generic initial conditions, loop corrections are UV divergent, making predictions cutoff dependent and hence unphysical.   I will present the systematic construction of an Effective Field Theory of Large Scale Structures and show that it successfully addresses all of the above issues. The idea is to smooth the density and velocity fields on a scale larger than the non-linear scale. The resulting smoothed fields are then small everywhere and provide a well-defined small parameter for perturbation theory. Smoothing amounts to integrating out the short scales, whose non-linear dynamics is hard to describe analytically. Their effects on the large scales are then determined by the symmetries of the problems. They introduce additional terms in the fluid equations such as an effective pressure, dissipation and stochastic noise. These terms have exactly the right scale dependence to cancel all divergences at one loop, and this should hold at all loops.
I will present a clean example of the renormalization of the theory in an Einstein de Sitter universe with self-similar initial conditions and discuss the relative importance of loop and effective corrections.