CERN-TH/2003-307
astro-ph/0312614

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Abstract. Cosmology, high-energy physics and astrophysics are converging on the study of large-scale magnetic fields. While the experimental evidence for the existence of large-scale magnetization in galaxies, clusters and superclusters is rather compelling, the origin of the phenomenon remains puzzling especially in light of the most recent observations. The purpose of the present review is to describe the physical motivations and some of the open theoretical problems related to the existence of large-scale magnetic fields.

Table of Contents

• A TRIPLE POINT
• FROM ALFVÉN TO ROSAT
• LARGE-SCALE MAGNETIC FIELDS OBSERVATIONS
• Zeeman splitting
• Synchrotron emission
• Faraday Rotation Measurements
• Magnetic fields in the Milky Way
• Magnetic fields in external galaxies
• Magnetic fields in Abell clusters
• Magnetic fields in superclusters
• GLOBALLY NEUTRAL PLASMAS
• Qualitative aspects of plasma dynamics
• Kinetic and fluid descriptions
• From one-fluid equations to MHD
• The Alfvén theorems
• Magnetic diffusivity equation
• The dynamo mechanism
• MAGNETIC FIELDS IN CURVED BACKGROUNDS
• The standard cosmological model
• Gauge fields in FRW Universes
• Physical scales in the evolution of magnetic fields
• Charge and current density fluctuations
• Inverse cascades
• Hypermagnetic fields
• TWO APPROACHES TO THE ORIGIN
• Inhomogeneous MHD equations
• Inflationary mechanisms
• Inside the Hubble radius
• Mixed mechanisms
• EFFECTS OF PRIMORDIAL MAGNETIC FIELDS
• Electroweak epoch
• Big-bang nucleosynthesis epoch
• CMB PHYSICS AN MAGNETIC FIELDS
• Large-scale magnetic fields and CMB anisotropies
• Faraday rotation of CMB
• Relic gravitational waves
• GRAVITATING MAGNETIC FIELDS
• CONCLUDING REMARKS
• COMPLEMENTS ON MHD DESCRIPTION
• REFERENCES