Phys. Rev. D 69, 063006 (2004) [20 pages]Cosmic microwave background and helical magnetic fields: The tensor modeReceived 25 April 2003; revised 4 November 2003; published 24 March 2004 We study the effect of a helicity component of a primordial magnetic field on the tensor part of the cosmic microwave background temperature anisotropies and polarization. We give analytical approximations for the tensor contributions induced by helicity, discussing their amplitude and spectral index in dependence of the power spectrum of the primordial magnetic field. We find that an helical magnetic field creates a parity odd component of gravity waves inducing parity odd polarization signals. However, only if the magnetic field is close to scale invariant and if its helical part is close to maximal, the effect is sufficiently large to be observable. We also discuss the implications of causality on the magnetic field spectrum. © 2004 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevD.69.063006
DOI:
10.1103/PhysRevD.69.063006
PACS:
98.70.Vc, 98.62.En, 98.80.Cq
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