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Statistical properties of scale-invariant helical magnetic fields and applications to cosmology
KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.ORCID iD: 0000-0002-7304-021X
Univ Geneva, Dept Phys Theor, Quai E Ansermet 24, CH-1211 Geneva 4, Switzerland.;Univ Geneva, Ctr Astroparticle Phys, Quai E Ansermet 24, CH-1211 Geneva 4, Switzerland..
Carnegie Mellon Univ, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA.;Carnegie Mellon Univ, Dept Phys, 5000 Forbes Ave, Pittsburgh, PA 15213 USA.;Laurentian Univ, Dept Phys, Ramsey Lake Rd, Sudbury, ON P3E 2C6, Canada.;Ilia State Univ, Abastumani Astrophys Observ, 3-5 Cholokashvili St, Tbilisi 0194, Rep of Georgia..
Carnegie Mellon Univ, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA.;Carnegie Mellon Univ, Dept Phys, 5000 Forbes Ave, Pittsburgh, PA 15213 USA..
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2018 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 8, article id 034Article in journal (Refereed) Published
Abstract [en]

We investigate the statistical properties of isotropic, stochastic, Gaussian distributed, helical magnetic fields characterized by different shapes of the energy spectra at large length scales and study the associated realizability condition. We discuss smoothed magnetic fields that are commonly used when the primordial magnetic field is constrained by observational data. We are particularly interested in scale-invariant magnetic fields that can be generated during the inflationary stage by quantum fluctuations. We determine the correlation length of such magnetic fields and relate it to the infrared cutoff of perturbations produced during inflation. We show that this scale determines the observational signatures of the inflationary magnetic fields on the cosmic microwave background. At smaller scales, the scale-invariant spectrum changes with time. It becomes a steeper weak-turbulence spectrum at progressively larger scales. We show numerically that the critical length scale where this happens is the turbulent-diffusive scale, which increases with the square root of time.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2018. no 8, article id 034
Keywords [en]
Magnetohydrodynamics, primordial magnetic fields, CMBR polarisation, physics of the early universe
National Category
Fusion, Plasma and Space Physics
Identifiers
URN: urn:nbn:se:kth:diva-234622DOI: 10.1088/1475-7516/2018/08/034ISI: 000442637500001Scopus ID: 2-s2.0-85053048248OAI: oai:DiVA.org:kth-234622DiVA, id: diva2:1247817
Note

QC 20180913

Available from: 2018-09-13 Created: 2018-09-13 Last updated: 2018-10-16Bibliographically approved

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