Helical primordial magnetic fields produce a computable parity-odd signal in the scalar trispectrum, currently constrained to r_H ≲ 4×10^-4 for B_r = 4.7 nG.
Intergalactic magnetic field spectra from diffuse gamma rays
1 Pith paper cite this work. Polarity classification is still indexing.
abstract
Non-vanishing parity-odd correlators of gamma ray arrival directions observed by Fermi-LAT indicate the existence of a helical intergalactic magnetic field (Tashiro et al.2013). We successfully test this hypothesis using more stringent cuts of the data, Monte Carlo simulations with Fermi-LAT time exposure information, separate analyses for the northern and southern galactic hemispheres, and confirm predictions made in Tashiro & Vachaspati (2014). With some further technical assumptions, we show how to reconstruct the magnetic helicity spectrum from the parity-odd correlators.
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Parity-violating scalar trispectrum from helical primordial magnetic fields
Helical primordial magnetic fields produce a computable parity-odd signal in the scalar trispectrum, currently constrained to r_H ≲ 4×10^-4 for B_r = 4.7 nG.