Cosmological magnetic field survival

Abstract

It is widely believed that primordial magnetic fields are dramatically diluted by the expansion of the universe. As a result, cosmological magnetic fields with residual strengths of astrophysical relevance are generally sought by going outside standard cosmology, or by extending conventional electromagnetic theory. Nevertheless, the survival of strong B-fields of primordial origin is possible in spatially open Friedmann universes without changing conventional electromagnetism. The reason is the hyperbolic geometry of these spacetimes, which slows down the adiabatic magnetic decay-rate and leads to their superadiabatic amplification on large scales. So far, the effect has been found to operate on Friedmannian backgrounds containing either radiation or a slow-rolling scalar field. We show here that the superadiabatic amplification of large-scale magnetic fields, generated by quantum fluctuations during inflation, is essentially independent of the type of matter that fills the universe and appears to be a generic feature of open Friedmann spacetimes. We estimate the late-time strength of any residual field in a marginally open universe and show that it can easily meet the requirements for the dynamo generation of the magnetic fields observed in galaxies today.

Equations streamlined, references updated. MNRAS in press

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• Magneto-reheating constraints from curvature perturbations
• On the challenges in the choice of the non-conformal coupling function in inflationary magnetogenesis
• Generation of large-scale magnetic fields, non-Gaussianity, and primordial gravitational waves in inflationary cosmology
• Helical magnetic fields from Riemann coupling
• Evolution of primordial magnetic fields in mean-field approximation
• Generation of large-scale magnetic fields from inflation in teleparallelism
• Conservation laws and evolution schemes in geodesic, hydrodynamic and magnetohydrodynamic flows
• Anisotropic power-law inflation for a conformal-violating Maxwell model
• Mode Spectrum of the Electromagnetic Field in Open Universe Models
• Do intergalactic magnetic fields imply an open universe?
• Superhorizon magnetic fields
• A Holographic Bound on Cosmic Magnetic Fields
• Bianchi Class B Spacetimes with Electromagnetic Fields
• Can a marginally open universe amplify magnetic fields?
• Evolution of magnetic fields through cosmological perturbation theory
• Is there supercurvature mode of massive vector field in open inflation?
• Large-scale magnetic fields from inflation due to a $CPT$-even Chern-Simons-like term with Kalb-Ramond and scalar fields
• Causality, initial conditions, and inflationary magnetogenesis
• Hilltop inflation and generation of helical magnetic field
• Holography of Little Inflation
• Relaxing the limits on inflationary magnetogenesis
• Constraints on a cubic Galileon disformally coupled to Standard Model matter
• Thermal enhancement of inflationary magnetic fields