# 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/en/arxiv-id/2309.06477v1/

## Key points

- Authors explore a technique for accessing high-redshift information in lensing reconstruction maps from the CMB
- Lensing maps provide direct observations of matter distribution without biased tracers
- Low-redshift contributions dominate these observables
- Proposed linear combination of lensing maps from CMB and LIM observations nullifies low-redshift contribution
- Nulling technique can place competitive constraints on standard ΛCDM plus neutrino mass parameters
- LIM-nulling is a powerful tool for cosmological studies and offers insights into the high-redshift universe beyond ΛCDM cosmology
- Enables model-independent tests of cosmology and provides insights into the high-redshift matter power spectrum.

## Summary

In their paper titled "Constraining Cosmology With the CMB × LIM-Nulling Convergence," authors Hannah Fronenberg, Abhishek S. Maniyar, Anthony R. Pullen, and Adrian Liu explore a novel technique for accessing high-redshift information in lensing reconstruction maps from the cosmic microwave background (CMB). These maps provide direct observations of the matter distribution of the universe without relying on biased tracers. However, these observables are dominated by their low-redshift contributions. To overcome this limitation and access high-redshift information more cleanly, Maniyar et al. propose a linear combination of lensing maps from both CMB and line intensity mapping (LIM) observations. This combination can effectively nullify the low-redshift contribution to CMB lensing convergence. In their study, the authors investigate the scientific returns of this nulling technique and demonstrate that estimators based on LIM-nulling can place competitive constraints on standard ΛCDM plus neutrino mass parameters when compared to traditional CMB lensing techniques. This highlights the potential of LIM-nulling as a powerful tool for cosmological studies and shows that it can serve as a clean probe of the high-redshift universe beyond ΛCDM cosmology. It enables model-independent tests of cosmology and offers insights into the high-redshift matter power spectrum. Overall, this paper presents an innovative approach to accessing high-redshift information in CMB lensing reconstruction maps using a combination of CMB and LIM observations with promising results for constraining cosmological parameters and probing beyond ΛCDM cosmology at high redshifts.