2008

Faraday Rotation Limits on a Primordial Magnetic Field from WMAP Five-Year Data

Kahniashvili, Tina, Maravin, Yurii, Kosowsky, Arthur

Understand

A primordial magnetic field in the early universe will cause Faraday rotation of the linear polarization of the cosmic microwave background generated via Compton scattering at the surface of last scattering.

  • This rotation induces a non-zero parity-odd (B-mode) polarization component.
  • The Wilkinson Microwave Anisotropy Probe (WMAP) 5-year data puts an upper limit on the magnitude of the B-polarization power spectrum; assuming that the B-polarization signal is totally due to the Faraday rotation effect, the upper limits on the comoving amplitude of a primordial stochastic magnetic field range from $6 \times 10^{-8}$ to $2 \times 10^{-6}$ G on a comoving length scale of 1 Mpc, depending on the power spectrum of the magnetic field.

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