Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Where do IceCube neutrinos come from? Hints from the diffuse gamma-ray
  flux   Despite the spectacular discovery of an astrophysical neutrino flux by
IceCube in 2013, its origin remains a mystery. Whatever its sources, we expect
the neutrino flux to be accompanied by a comparable gamma-ray flux. These
photons should be degraded in energy by electromagnetic cascades and contribute
to the diffuse GeV-TeV flux precisely measured by the Fermi-LAT. Population
studies have also permitted to identify the main classes of contributors to
this flux, which at the same time have not been associated with major neutrino
sources in cross-correlation studies. These considerations allow one to set
constraints on the origin and spectrum of the IceCube flux, in particular its
low-energy part. We find that, even accounting for known systematic errors, the
Fermi-LAT data exclude to at least 95% C.L. any extragalactic transparent
source class, irrespective of its redshift evolution, if the neutrino spectrum
extends to the TeV scale or below. If the neutrino spectrum has an abrupt
cutoff at $\sim10$ TeV, barely compatible with current observations, the
tension can be reduced, but this way out requires a significant modification to
the current understanding of the origin of the diffuse extragalactic gamma-ray
flux at GeV energies. In contrast, these considerations do not apply if a
sizable fraction of IceCube data originates within the Galactic halo (a
scenario however typically in tension with other constraints) or from a yet
unidentified class of "opaque" extragalactic emitters, which do not let the
high-energy gamma rays get out.

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The categories of this paper are: cond-mat
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The categories of this paper are: econ
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The categories of this paper are: nucl-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
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The categories of this paper are: hep-th
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: acc-phys