Magnetic field back reaction on the matter power spectrum

TL;DR

This paper investigates how the back reaction of magnetic fields influences the evolution of matter perturbations and the matter power spectrum at small scales in the universe.

Contribution

It introduces a detailed analysis of the magnetic field back reaction effects on the matter power spectrum, including the evolution of magnetic fields and their cross correlations with curvature modes.

Findings

Magnetic back reaction affects small-scale matter power spectrum.

Induces cross correlations between curvature and magnetic modes.

Magnetic fields evolve non-trivially due to baryon interactions.

Abstract

At lowest order comoving magnetic fields which are frozen-into the expanding cosmic fluid do not evolve in time. At next-to-leading order the induction equation is sourced by the interaction term between the baryon velocity and the magnetic field amplitude which leads to a non-trivial evolution of the comoving magnetic field. Moreover, it induces non-trivial cross correlations between the adiabatic curvature mode and the magnetic mode. This cross correlation together with the evolution of the induced matter perturbation leads to interesting effects on the total matter power spectrum at small scales.