Parity-odd correlators of diffuse gamma rays and intergalactic magnetic
  fields
  We develop the connection between intergalactic helical magnetic fields and
parity odd signatures in the diffuse gamma ray sky. We find that the location
and the amplitude of a peak in a parity odd correlator, $Q(R)$, can be used to
infer the normal and helical power spectra of the intergalactic magnetic field.
When applied to Fermi-LAT data, the amplitude of the observed peak in $Q(R)$
gives $\sim 10^{-14}~{\rm G}$ intergalactic magnetic field strength, which is
consistent with an earlier independent estimate that only used the peak
location (Tashiro et al. 2014). We discuss features in the observed $Q(R)$ that
further support the intergalactic magnetic field hypothesis and make
predictions for future tests.
