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Evolution of primordial magnetic fields from phase transitions
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.ORCID iD: 0000-0002-7304-021X
2013 (English)In: Physical Review D, ISSN 1550-7998, Vol. 87, no 8, 083007- p.Article in journal (Refereed) Published
Abstract [en]

We consider the evolution of primordial magnetic fields generated during cosmological, electroweak, or QCD phase transitions. We assume that the magnetic field generation can be described as an injection of magnetic energy to cosmological plasma at a given scale determined by the moment of magnetic field generation. A high Reynolds number ensures strong coupling between the magnetic field and fluid motions. The subsequent evolution of the magnetic field is governed by decaying hydromagnetic turbulence. Both our numerical simulations and a phenomenological description allow us to recover "universal'' laws for the decay of magnetic energy and the growth of magnetic correlation length in the turbulent (low-viscosity) regime. In particular, we show that during the radiation-dominated epoch, the energy and correlation length of nonhelical magnetic fields scale as conformal time to the powers -1/2 and +1/2, respectively. For helical magnetic fields, the energy and correlation length scale as conformal time to the powers -1/3 and +2/3, respectively. The universal decay law of the magnetic field implies that the strength of the magnetic field generated during the QCD phase transition could reach similar to 10(-9) G with the present-day correlation length similar to 50 kpc. The fields generated at the electroweak phase transition could be as strong as similar to 10(-10) G with correlation lengths reaching similar to 0.3 kpc. These values of the magnetic fields are consistent with the lower bounds of the extragalactic magnetic fields.

Place, publisher, year, edition, pages
2013. Vol. 87, no 8, 083007- p.
Keyword [en]
Tev Blazars, Magnetohydrodynamic Turbulence, Alfvenic Turbulence, Constraints, Generation, Radiation, Helicity, Universe, Energy, Origin
National Category
Physical Sciences
URN: urn:nbn:se:kth:diva-122513DOI: 10.1103/PhysRevD.87.083007ISI: 000317829200002ScopusID: 2-s2.0-84877123389OAI: diva2:622904
Swedish Research Council, 621-2007-4064EU, European Research Council, 227952

QC 20130523

Available from: 2013-05-23 Created: 2013-05-23 Last updated: 2013-08-28Bibliographically approved

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Brandenburg, Axel
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