Résumé
While the simplest inflationary models predict a power-law form of the
primordial power spectrum (PPS), various UV complete scenarios predict features
on top of the standard power law that leave characteristic imprints in the
late-time distribution of matter, encoded in the galaxy power spectrum. In this
work, we assess the validity of the Effective Field Theory of Large Scale
Structure (EFTofLSS) and the IR-resummation scheme of PyBird in the context of
primordial (oscillatory) features. We find an excellent agreement at the level
of the matter power spectrum between N-body simulations and the one-loop EFT
predictions, for models commonly studied in the literature. We then apply the
EFTofLSS to the galaxy power spectrum measurements from BOSS LRG and eBOSS QSO
to constrain specific global and local features in the PPS. We demonstrate that
while such features can improve the fit to cosmic microwave background (CMB)
data, they may result in a poorer fit to clustering measurements at low
redshift. The resulting constraints on the amplitude of the primordial
oscillations are competitive with those obtained from CMB data, despite the
well-known damping of oscillations due to non-linear structure formation
processes. For the first time in this context, we jointly analyze the galaxy
power spectrum (monopole and quadrupole) in combination with Planck CMB data to
derive strong constraints on the amplitude of primordial features. This work
highlights the EFTofLSS as a powerful tool for testing early universe scenarios
on scales that complement CMB observations.