Cosmology at high redshift -- a probe of fundamental physics

TL;DR

This paper forecasts how high-redshift universe observations can significantly improve constraints on fundamental cosmological parameters using advanced Fisher matrix techniques and compares these with current survey capabilities.

Contribution

It introduces a Fisher matrix formalism based on Lagrangian perturbation theory for forecasting high-redshift survey constraints and provides a publicly available Python tool.

Findings

Forecasts improved constraints on cosmological parameters at high redshift.

Demonstrates the effectiveness of the Fisher matrix approach with Lagrangian perturbation theory.

Provides a comparison with current survey capabilities like DESI and Euclid.

Abstract

An observational program focused on the high redshift ($2<z<6$) Universe has the opportunity to dramatically improve over upcoming LSS and CMB surveys on measurements of both the standard cosmological model and its extensions. Using a Fisher matrix formalism that builds upon recent advances in Lagrangian perturbation theory, we forecast constraints for future spectroscopic and 21-cm surveys on the standard cosmological model, curvature, neutrino mass, relativistic species, primordial features, primordial non-Gaussianity, dynamical dark energy, and gravitational slip. We compare these constraints with those achievable by current or near-future surveys such as DESI and Euclid, all under the same forecasting formalism, and compare our formalism with traditional linear methods. Our Python code FishLSS $-$ used to calculate the Fisher information of the full shape power spectrum, CMB lensing, the cross-correlation of CMB lensing with galaxies, and combinations thereof $-$ is publicly available.