Evolution of primordial magnetic fields from phase transitions

Kahniashvili, Tina and Tevzadze, Alexander and Brandenburg, Axel and Neronov, Andrii (2013) Evolution of primordial magnetic fields from phase transitions. Physical Review D, 87.


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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 ˜10-9G with the present-day correlation length ˜50kpc. The fields generated at the electroweak phase transition could be as strong as ˜10-10G with correlation lengths reaching ˜0.3kpc. These values of the magnetic fields are consistent with the lower bounds of the extragalactic magnetic fields.

Item Type: Article
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Depositing User: Prof. Tina Kahniashvili
Date Deposited: 29 Jan 2014 20:44
Last Modified: 27 Mar 2015 07:09
URI: http://eprints.iliauni.edu.ge/id/eprint/773

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