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Published Online January 5, 2006
Science DOI: 10.1126/science.1120690

Reports

Submitted on September 28, 2005
Accepted on December 12, 2005

Cosmological Magnetic Field: A Fossil of Density Perturbations in the Early Universe

Kiyotomo Ichiki 1*, Keitaro Takahashi 2, Hiroshi Ohno 3, Hidekazu Hanayama 4, Naoshi Sugiyama 5

1 National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA; Research Fellows of Japan Society for the Promotion of Science.
2 Research Fellows of Japan Society for the Promotion of Science; Department of Physics, Princeton University, Princeton, NJ 08544, USA.
3 Corporate Research and Development Center, Toshiba Corporation, Kawasaki 212-8582, Japan.
4 National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan; Department of Astronomy, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
5 National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan.

* To whom correspondence should be addressed.
Kiyotomo Ichiki , E-mail: ichiki{at}th.nao.ac.jp

The origin of substantial magnetic fields found in galaxies and on even larger scales such as in clusters of galaxies is yet unclear. Cosmological density fluctuations, which explain the large scale structure of the universe, can also produce magnetic fields on cosmological scales before the epoch of recombination if the second order couplings between photons and electrons are taken into account. Evaluating the power spectrum of these cosmological magnetic fields on a range of scales we show that magnetic fields of 10-16.8 Gauss are generated at 1 Mpc scale and can be even stronger at smaller scales (10-12.8 Gauss at 10 kpc). They are large enough to seed magnetic fields in galaxies, and may therewith have affected primordial star formation in the early universe.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)