# Flavour composition and entropy increase of cosmological neutrinos after decoherence

## TL;DR

This paper explores how gravitational interactions cause decoherence in cosmological neutrinos, leading to increased entropy and altered flavor composition, with potential observational implications.

## Contribution

It introduces a model of neutrino decoherence due to gravitational fluctuations using a Lindblad operator, analyzing its effects on flavor composition and entropy.

## Key findings

- Neutrino entropy increases with initial spectral distortions and mixing parameters.
- Decoherence alters the expected flavor composition of cosmic neutrinos.
- Potential observational signatures of neutrino decoherence are discussed.

## Abstract

We propose that gravitational interactions of cosmic neutrinos with the statistically homogeneous and isotropic fluctuations of space-time leads to decoherence. This working hypothesis, which we describe by means of a Lindblad operator, is applied to the system of two- and three-flavour neutrinos undergoing vacuum oscillations and the consequences are investigated. As result of this decoherence we find that the neutrino entropy would increase as a function of initial spectral distortions, mixing angles and CP-violation phase. Subsequently we discuss the chances to discover such an increase observationally (in principle). We also present the expected flavour composition of the cosmic neutrino background after decoherence is completed. The physics of two- or three-flavour oscillation of cosmological neutrinos resembles in many aspects two- or three-level systems in atomic clocks, which were recently proposed by Weinberg for the study of decoherence phenomena.