2016/01/06 by Kouichirou Horiguchi, Kiyotomo Ichiki, Horiguchi, Kouichirou +3 · 1 citation
Physics and Astronomy · #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #astro-ph.CO
paper · pdf · doi:10.48550/arxiv.1601.01059
17 pages, 3 figures
arxiv created 2016/01/06 · arxiv updated 2016/01/07
Cosmic strings are a type of cosmic defect formed by a symmetry-breaking phase transition in the early universe. Individual strings would have gathered to build a network, and their dynamical motion would induce scalar--, vector-- and tensor--type perturbations. In this paper, we focus on the vector mode perturbations arising from the string network based on the one scale model and calculate the time evolution and the power spectrum of the associated magnetic fields. We show that the relative velocity between photon and baryon fluids induced by the string network can generate magnetic fields over a wide range of scales based on standard cosmology. We obtain the magnetic field spectrum before recombination as a2B(k,z)∼4×10-16Gμ/((1+z)/1000)4.25(k/\rm Mpc-1)3.5 Gauss on super-horizon scales, and a2B(k,z)∼2.4×10-17Gμ/((1+z)/1000)3.5(k/\rm Mpc-1)2.5 Gauss on sub-horizon scales in co-moving coordinates. This magnetic field grows up to the end of recombination, and has a final amplitude of approximately B∼10-17∼ -18 Gμ Gauss at the k∼1 \rm Mpc-1 scale today. This field might serve as a seed for cosmological magnetic fields.