# Lorentz invariance violation in the neutrino sector: a joint analysis from big bang nucleosynthesis and the cosmic microwave background

## TL;DR

This paper constrains Lorentz invariance violation in the neutrino sector by combining big bang nucleosynthesis and cosmic microwave background data, revealing strong limits on possible deviations from standard physics.

## Contribution

It provides the first joint analysis of BBN and CMB data to constrain Lorentz invariance violation in neutrinos, breaking degeneracies with dark matter density.

## Key findings

- Primordial helium-4 abundance constrains Lorentz violation parameters.
- Planck 2015 data combined with helium measurements yields strong limits.
- Degeneracy between Lorentz violation and dark matter density is broken.

## Abstract

We investigate constraints on Lorentz invariance violation in the neutrino sector from a joint analysis of big bang nucleosynthesis and the cosmic microwave background. The effect of Lorentz invariance violation during the epoch of big bang nucleosynthesis changes the predicted helium-4 abundance, which influences the power spectrum of the cosmic microwave background at the recombination epoch. In combination with the latest measurement of the primordial helium-4 abundance, the Planck 2015 data of the cosmic microwave background anisotropies give a strong constraint on the deformation parameter since adding the primordial helium measurement breaks the degeneracy between the deformation parameter and the physical dark matter density.