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

¹e-mail address: massimo.giovannini@cern.ch Back.