Early cosmological evolution of primordial electromagnetic fields

Takeshi Kobayash, Martin Snoager Sloth*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

It is usually assumed that when Weyl invariance is unbroken in the electromagnetic sector, the energy density of primordial magnetic fields will redshift as radiation. Here we show that primordial magnetic fields do not exhibit radiationlike redshifting in the presence of stronger electric fields, as a consequence of Faraday's law of induction. In particular for the standard Maxwell theory, magnetic fields on superhorizon scales can redshift as B2a-6H-2, instead of the usually assumed a-4. Taking into account this effect for inflationary magnetogenesis can correct previous estimates of the magnetic field strength by up to 37 orders of magnitude. This opens new possibilities for inflationary magnetogenesis, and as an example we propose a scenario where femto-Gauss intergalactic magnetic fields are created on Mpc scales, with high-scale inflation producing observable primordial gravitational waves, and reheating happening at low temperatures.

Original languageEnglish
Article number 023524
JournalPhysical Review D
Volume100
Issue number2
Number of pages16
ISSN2470-0010
DOIs
Publication statusPublished - 15. Jul 2019

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