# Measuring the growth of structure with intensity mapping surveys

## TL;DR

This paper proposes a method to break degeneracies in intensity mapping measurements, enabling precise constraints on cosmological parameters by utilizing mildly non-linear regime information.

## Contribution

It introduces a novel approach using Lagrangian Perturbation Theory to disentangle astrophysical and cosmological signals in intensity mapping data.

## Key findings

- Potential to constrain the amplitude of fluctuations at the percent level
- Demonstrates feasibility with 21-cm line surveys like HIRAX and Stage II
- Shows how to leverage mildly non-linear regime information

## Abstract

Line intensity mapping offers a new avenue for constraining cosmological parameters in the high redshift Universe. However measurements of the growth of structure, a sensitive probe of gravity, are affected by a well known degeneracy with astrophysical parameters, encoded in the mean brightness temperature of the specific line. In this work we show how to break this degeneracy, to a level that could allow constraints of the amplitude of cosmological fluctuations at the percent level, using information in the mildly non-linear regime of structure formation as described by Lagrangian Perturbation Theory. We focus on the 21-cm line with forecasts for HIRAX and the proposed Stage II experiment as illustrations.