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Published November 26, 2012 | Published
Journal Article Open

First CMB constraints on direction-dependent cosmological birefringence from WMAP-7


A Chern-Simons coupling of a new scalar field to electromagnetism may give rise to cosmological birefringence, a rotation of the linear polarization of electromagnetic waves as they propagate over cosmological distances. Prior work has sought this rotation, assuming the rotation angle to be uniform across the sky, by looking for the parity-violating TB and EB correlations that a uniform rotation produces in the cosmic microwave background temperature/polarization. However, if the scalar field that gives rise to cosmological birefringence has spatial fluctuations, then the rotation angle may vary across the sky. Here we search for direction-dependent cosmological birefringence in the WMAP-7 data. We report the first cosmic microwave background constraint on the rotation-angle power spectrum C^(αα)_L for multipoles between L=0 and L=512. We also obtain a 68% confidence-level upper limit of √(C^(αα)_(2)/(4π))≲1° on the quadrupole of a scale-invariant rotation-angle power spectrum.

Additional Information

© 2012 American Physical Society. Received 24 June 2012; published 26 November 2012. This work was supported by DOE DE-FG03-92-ER40701, NASA NNX12AE86G, DOE (DOE.DESC0006624), and the David and Lucile Packard Foundation. Part of the research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Some of the results in this paper have been derived using the HEALPix package.

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Published - PhysRevD.86.103529.pdf


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