Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the intensity and spatial morphology of the 511 keV emission in the
  Milky Way   The positron emissivity of the Galactic bulge and disk, resulting from
radioactivity of SNIa, is reassessed in the light of a recent evaluation of the
SNIa rate. It is found that the disk may supply more positrons than required by
recent SPI/INTEGRAL observations, but the bulge (where the characteristic
positron annihilation line at 511 keV is in fact observed) only about 10%. It
is argued that a large fraction of the disk positrons may be transported via
the regular magnetic field of the Galaxy into the bulge, where they annihilate.
This would increase both the bulge emissivity and the bulge/disk ratio,
alleviating considerably the constraints imposed by INTEGRAL data analysis. We
argue that the bulge/disk positron emissivity ratio can be considerably smaller
than the values derived by the recent analysis of Knoedlseder et al. (2005), if
the disk positrons diffuse sufficiently away from their sources, as required by
our model; this possibility could be tested in the future, as data are
accumulated in the SPI detectors. The success of the proposed scenario depends
critically upon the, very poorly known at present, properties of the galactic
magnetic field and of the propagation of low energy positrons in it.

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The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
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The categories of this paper are: stat
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
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The categories of this paper are: hep-th
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: quant-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom