Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A unified model for the time variability of the Crab: the dispersion
  measure variation and the $\gamma$-ray flare of the nebula   The Crab pulsar and its nebula are very luminous and variable. Since 1982,
random fluctuations of the dispersion measure (DM) have been recorded. Also in
2011, Fermi-LAT telescope detected $\gamma$-ray flux variation of the Crab
nebula. No correlation between these phenomena have considered although their
fluctuating patterns look similar. We propose a model which connects the DM and
the Crab nebula $\gamma$-ray flux fluctuation, motivated by recently reported
correlation between the braking index and the DM variability. Considering
electrons within the inner shock region of the nebula produced in breaking
index change events, we can explain both the DM enhancement and the
$\gamma$-ray flare in a simple way.

24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
25
The categories of this paper are: patt-sol