# Constraining Cosmology With the CMB $\times$ LIM-Nulling Convergence

**Authors:** Hannah Fronenberg, Abhishek S. Maniyar, Anthony R. Pullen, Adrian Liu  
**arXiv:** [2309.06477](https://arxiv.org/abs/2309.06477)  
**Date:** 2023-09-12  
**Summary page:** https://www.summarizepaper.com/fr/arxiv-id/2309.06477v1/

## Abstract

Lensing reconstruction maps from the cosmic microwave background (CMB) provide direct observations of the matter distribution of the universe without the use of a biased tracer. Such maps, however, constitute projected observables along the line of sight that are dominated by their low-redshift contributions. To cleanly access high-redshift information, Maniyar et al. showed that a linear combination of lensing maps from both CMB and line intensity mapping (LIM) observations can exactly null the low-redshift contribution to CMB lensing convergence. In this paper we explore the scientific returns of this nulling technique. We show that LIM-nulling estimators can place constraints on standard $\Lambda$CDM plus neutrino mass parameters that are competitive with traditional CMB lensing. Additionally, we demonstrate that as a clean probe of the high-redshift universe, LIM-nulling can be used for model-independent tests of cosmology beyond $\Lambda$CDM and as a probe of the high-redshift matter power spectrum.