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Published December 29, 2011 | Published
Journal Article Open

Correlation of inflation-produced magnetic fields with scalar fluctuations


If the conformal invariance of electromagnetism is broken during inflation, then primordial magnetic fields may be produced. If this symmetry breaking is generated by the coupling between electromagnetism and a scalar field—e.g. the inflaton, curvaton, or Ricci scalar—then these magnetic fields may be correlated with primordial density perturbations, opening a new window to the study of non-Gaussianity in cosmology. In order to illustrate, we couple electromagnetism to an auxiliary scalar field in a de Sitter background. We calculate the power spectra for scalar-field perturbations and magnetic fields, showing how a scale-free magnetic-field spectrum with rms amplitude of ∼nG at Mpc scales may be achieved. We explore the Fourier-space dependence of the cross correlation between the scalar field and magnetic fields, showing that the dimensionless amplitude, measured in units of the power spectra, can grow as large as ∼500H_I/M, where H_I is the inflationary Hubble constant and M is the effective mass scale of the coupling.

Additional Information

© 2011 American Physical Society. Received 27 September 2011; published 29 December 2011. M. K. thanks the Miller Institute for Basic Research in Science for support and the Department of Physics at the University of California, Berkeley, where part of this work was completed, for hospitality. R.C. and L. M. thank Caltech for hospitality, where part of this work was completed. This work was supported in part by NSF Grant No. AST-0349213 at Dartmouth College and by DOE Grant No. DE-FG03-92-ER40701, NASA Grant No. NNX10AD04G, and the Gordon and Betty Moore Foundation at Caltech.

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