Constraints on the Primordial Magnetic Field from $\sigma_8$

TL;DR

This paper constrains the properties of primordial magnetic fields by analyzing their impact on density fluctuations in the early universe and comparing with observational data such as galaxy number density fluctuations.

Contribution

It provides new constraints on the amplitude and spectral index of primordial magnetic fields using cosmological density fluctuation data.

Findings

Strong limits on PMF amplitude $B_$ from $\sigma_8$ constraints

Constraints on the spectral index $n_ ext{B}$ of the PMF

Implications for early universe magnetic field models

Abstract

A primordial magnetic field (PMF) can affect the evolution of density field fluctuations in the early universe.In this paper we constrain the PMF amplitude $B_\lambda$ and power spectral index $n_\mathrm{B}$ by comparing calculated density field fluctuations with observational data, i.e. the number density fluctuation of galaxies.We show that the observational constraints on cosmological density fluctuations, as parameterized by $\sigma_8$, lead to strong constraints on the amplitude and spectral index of the PMF.