Constraints on the Primordial Magnetic Field from ${\sigma }_8$

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.

Comments: 11 pages, 1 figure, accepted for publication as Phys. Rev. D