# Lensing anomalies from the epoch of reionisation

## TL;DR

This paper investigates reionisation blurring, a non-linear correction to the CMB similar to lensing, analyzing its impact and correlation with lensing potential, and its potential to cause observable anomalies.

## Contribution

It provides the first comprehensive calculation of reionisation blurring's effect on the CMB temperature power spectrum and its correlation with lensing potential.

## Key findings

- Reionisation blurring's impact is about two orders of magnitude smaller than lensing.
- Reionisation blurring is strongly correlated with lensing potential.
- It can potentially induce observable lensing anomalies.

## Abstract

Reionisation blurring is a non-linear correction to the cosmic microwave background that acts similar to weak gravitational lensing and that can be computed from linear perturbations through a blurring potential. Its impact on the cosmic microwave background is roughly two order of magnitude smaller than that of lensing, in isolation. But the blurring potential is strongly correlated with the lensing potential thereby generating a potentially observable cross-correlation. We compute for the first time the inclusive impact of reionisation blurring on the temperature angular power spectrum and discuss how much it could induce lensing anomalies