Non-standard neutrino cosmology dilutes the lensing anomaly

TL;DR

This paper explores how hypothetical long-range interactions among neutrinos could explain the CMB lensing anomaly, suggesting it may be a statistical fluctuation rather than new physics.

Contribution

It introduces a novel neutrino interaction model that impacts CMB lensing, providing a potential explanation for the lensing anomaly.

Findings

Neutrino interactions can significantly alter lensing patterns.

Lensing anomaly may be a statistical fluctuation.

Neutrino properties could be linked to observed anomalies.

Abstract

Despite the impressive success of the standard cosmological model, several anomalies defy its triumph. Among them is the so-called lensing anomaly: the Planck satellite observes stronger CMB gravitational lensing than expected. The role of neutrinos in this anomaly has been mostly overlooked, despite their key role in CMB lensing, because in the standard scenario they tend to increase the tension. Here, we show that this strongly depends on the assumed neutrino equation of state. We demonstrate that if neutrinos have yet undiscovered long-range interactions, the lensing pattern is significantly affected, rendering the lensing anomaly as a statistical fluctuation. Our results thus open up a window to link anomalous CMB lensing with present and future cosmological, astrophysical, and laboratory measurements of neutrino properties.