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arXiv · 1807.07477

Enhancing the cross-correlations between magnetic fields and scalar perturbations through parity violation

Debika Chowdhury·L. Sriramkumar·Marc Kamionkowski
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Abstract

One often resorts to a non-minimal coupling of the electromagnetic field in order to generate magnetic fields during inflation. The coupling is expected to depend on a scalar field, possibly the same as the one driving inflation. At the level of three-point functions, such a coupling leads to a non-trivial cross-correlation between the perturbation in the scalar field and the magnetic field. This cross-correlation has been evaluated analytically earlier for the case of non-helical electromagnetic fields. In this work, we numerically compute the cross-correlation for helical magnetic fields. Non-Gaussianities are often generated as modes leave the Hubble radius. The helical electromagnetic modes evolve strongly (when compared to the non-helical case) around Hubble exit and one type of polarization is strongly amplified immediately after Hubble exit. We find that helicity considerably boosts the amplitude of the dimensionless non-Gaussianity parameter that characterizes the amplitude and shape of the cross-correlation between the perturbations in the scalar field and the magnetic field. We discuss the implications of the enhancement in the non-Gaussianity parameter due to parity violation.

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Debika Chowdhury, L. Sriramkumar, Marc Kamionkowski. 2018-07-18. Enhancing the cross-correlations between magnetic fields and scalar perturbations through parity violation. https://doi.org/10.1088/1475-7516%2F2018%2F10%2F031

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