Probing Long-Range Forces Between Neutrinos with Cosmic Structures

TL;DR

This paper investigates how hypothetical long-range forces between neutrinos could influence cosmic structures, potentially leading to nonlinear bound states and affecting matter perturbations, with constraints derived from cosmological observations.

Contribution

It introduces the idea that strong long-range neutrino forces can cause perturbation instabilities and bound state formation, providing new cosmological constraints on such forces.

Findings

Long-range neutrino forces can induce perturbation instability.

Neutrino bound states may enhance matter perturbations.

Constraints on neutrino force range from 1 kpc to 10 Mpc.

Abstract

We study the consequences of new long-range forces between neutrinos on cosmic scales. If these forces are a few orders of magnitude stronger than gravity, they can induce perturbation instability in the non-relativistic cosmic neutrino background in the late time universe. As a result, the cosmic neutrino background may form nonlinear bound states instead of free-streaming. The implications of the formation of nonlinear neutrino bound states include enhancing matter perturbations and triggering star formation. Based on existing measurements of the matter power spectrum and reionization history, we place new constraints on long-range forces between neutrinos with ranges lying in $1 \text{ kpc}\lesssim m_\phi^{-1} \lesssim 10 \text{ Mpc}$.