Cosmological Perturbations and Effective Field Theory

Speaker: Lucia Fonseca, University of Sussex

Speaker arrival: 19/04/2017

Speaker departure: 21/04/2017

Assigned office: 23

Title: Cosmological Perturbations and Effective Field Theory

Place: Seminario del Dpto Física Teórica y del Cosmos

Date: 20/04/2017

Time: 12:00

Abstract:
The use of Eulerian “standard perturbation theory” to describe mass assembly in the early universe has traditionally been limited to modes with k < 0.1 h/Mpc at z=0. At larger k the SPT power spectrum deviates from measurements made using N-body simulations. Recently, there has been progress in extending the reach of perturbation theory to larger k using ideas borrowed from effective field theory. We revisit the computation of the real-space matter power spectrum within this framework. We use a re-summation scheme proposed by Vlah et al. to account for damping of baryon acoustic oscillations due to large-scale random motions and show that this has a significant effect on the multi-pole power spectra. However, real surveys estimate the radial distance to a source from its redshift, and therefore do not measure the galaxies' true spatial configuration. Unknown peculiar velocities associated with each source bias our distant estimate, producing a systematic 'redshift-space distortion'. Therefore, we feel the need of introducing the effective field theory formalism in redshift space. We re-normalize by comparison to a suite of custom N-body simulations matching the MultiDark MDR1 cosmology. At z=0 and for scales k <0.4 h/Mpc we find that the EFT furnishes a description of the real-space power spectrum up to ~2%, for the l=0 mode up to ~5%, and for the l=2,4 modes up to ~25%. We argue that, in the MDR1 cosmology, positivity of the l=0 mode gives a firm upper limit of k ~0.75 h/Mpc for the validity of the one-loop EFT prediction in redshift space using only the lowest-order counter-term.