Constraints on inflation with LSS surveys: features in the primordial power spectrum

TL;DR

Future large scale structure surveys, combined with CMB and weak lensing data, will significantly improve constraints on primordial features from inflation, surpassing current CMB-only limits and shedding light on deviations from scale invariance.

Contribution

This study forecasts the ability of upcoming LSS surveys to detect and constrain features in the primordial power spectrum, using a Fisher matrix analysis with multiple observables.

Findings

Combined data will tighten constraints on primordial features.

Surveys can probe features at scales relevant to known CMB anomalies.

Forecasts suggest improved detection of deviations from scale invariance.

Abstract

We analyse the efficiency of future large scale structure surveys to unveil the presence of scale dependent features in the primordial spectrum --resulting from cosmic inflation-- imprinted in the distribution of galaxies. Features may appear as a consequence of non-trivial dynamics during cosmic inflation, in which one or more background quantities experienced small but rapid deviations from their characteristic slow-roll evolution. We consider two families of features: localized features and oscillatory extended features. To characterise them we employ various possible templates parametrising their scale dependence and provide forecasts on the constraints on these parametrisations for LSST like surveys. We perform a Fisher matrix analysis for three observables: cosmic microwave background (CMB), galaxy clustering and weak lensing. We find that the combined data set of these observables will be able to limit the presence of features down to levels that are more restrictive than current constraints coming from CMB observations only. In particular, we address the possibility of gaining information on currently known deviations from scale invariance inferred from CMB data, such as the feature appearing at the $\ell \sim 20$ multipole (which is the main contribution to the low-$\ell$ deficit) and a potential feature appearing at $\ell \sim 800$.