Late-Time Magnetogenesis Driven by Axionlike Particle Dark Matter and a Dark Photon.

Kiwoon Choi,Hyungjin Kim,Toyokazu Sekiguchi

doi:10.1103/physrevlett.121.031102

Kiwoon Choi, Hyungjin Kim + Show 1 more

Open Access

https://doi.org/10.1103/physrevlett.121.031102

Copy DOI

Abstract

We propose a mechanism generating primordial magnetic fields after the e^{+}e^{-} annihilations. Our mechanism involves an ultralight axionlike particle (ALP) which constitutes the dark matter and a dark U(1)_{X} gauge boson introduced to bypass the obstacle placed by the conductivity of cosmic plasma. In our scheme, a coherently oscillating ALP amplifies the dark photon field, and part of the amplified dark photon field is concurrently converted to the ordinary magnetic field through the ALP-induced magnetic mixing. For the relevant ALP mass range 10^{-21} eV≲m_{ϕ}≲10^{-17} eV, our mechanism can generate B∼10^{-24} G(m_{ϕ}/10^{-17} eV)^{5/4} with a coherent length λ∼(m_{ϕ}/10^{-17} eV)^{-1/2} kpc, which is large enough to provide a seed of the galactic magnetic fields. The mechanism also predicts a dark U(1)_{X} electromagnetic field E_{X}∼B_{X}∼80 nG(m_{ϕ}/10^{-17} eV)^{-1/4}, which can result in interesting astrophysical or cosmological phenomena by inducing the mixings between the ALP, ordinary photon, and dark photon states.

Highlights

The origin of the primordial magnetic fields is one of the long-standing problems in modern cosmology
Our mechanism involves an ultralight axionlike particle (ALP) which constitutes the dark matter and a dark Uð1ÞX gauge boson introduced to bypass the obstacle placed by the conductivity of cosmic plasma
Inflationary magnetogenesis often suffers from the backreaction by the produced magnetic fields, which spoils the dynamics of inflaton or generates too large non-Gaussianity in primordial perturbations [15,16,17] [these problems can be circumvented if magnetogenesis takes place after the cosmic microwave background (CMB) scales exit the horizon [18,19]]

Summary

Introduction

The origin of the primordial magnetic fields is one of the long-standing problems in modern cosmology. For the relevant ALP mass range 10−21 eV ≲ mφ ≲ 10−17 eV, our mechanism can generate B ∼ 10−24 Gðmφ=10−17 eVÞ5=4 with a coherent length λ ∼ ðmφ=10−17 eVÞ−1=2 kpc, which is large enough to provide a seed of the galactic magnetic fields. The mechanism predicts a dark Uð1ÞX electromagnetic field EX ∼ BX ∼ 80 nGðmφ=10−17 eVÞ−1=4, which can result in interesting astrophysical or cosmological phenomena by inducing the mixings between the ALP, ordinary photon, and dark photon states.

Results

Conclusion