Getting leverage on inflation with a large photometric redshift survey

TL;DR

This paper evaluates how a future large photometric redshift survey combined with CMB data can significantly improve constraints on inflationary parameters, especially the spectral index and its running, surpassing current limits.

Contribution

It demonstrates the enhanced potential of combining multiple large-scale structure observables with CMB measurements to constrain inflationary parameters more precisely than before.

Findings

Spectral index n_s constrained to 0.0025 precision.

Running of spectral index constrained to 0.0017.

Combined probes break parameter degeneracies effectively.

Abstract

We assess the potential of a future large-volume photometric redshift survey to constrain observational inflationary parameters using three large-scale structure observables: the angular shear and galaxy power spectra, and the cluster mass function measured through weak lensing. When used in combination with Planck-like CMB measurements, we find that the spectral index n_s can be constrained to a 1 sigma precision of up to 0.0025. The sensitivity to the running of the spectral index can potentially improve to 0.0017, roughly a factor of five better than the present 1 sigma~constraint from Planck and auxiliary CMB data, allowing us to test the assumptions of the slow-roll scenario with unprecedented accuracy. Interestingly, neither CMB+shear nor CMB+galaxy nor CMB+clusters alone can achieve this level of sensitivity; it is the combined power of all three probes that conspires to break the different parameter degeneracies inherent in each type of observations. We make our forecast software publicly available via download or upon request from the authors.