Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Factors Determining Variability Time in Active Galactic Nucleus Jets   The relationship between observed variability time and emission region
geometry is explored for the case of emission by relativistic jets. The
approximate formula for the jet-frame size of the emission region, $R'=Dc\Delta
t_{\rm obs}$ is shown to lead to large systematic errors when used together
with observed luminosity and assumed or estimated Doppler factor $D$ to
estimate the jet-frame photon energy density. These results have implications
for AGN models in which low-energy photons are targets for interaction of high
energy particles and photons, e.g. synchrotron-self Compton models and hadronic
blazar models, as well as models of intra-day variable sources in which the
photon energy density imposes a brightness temperature limit through Compton
scattering.
  The actual relationship between emission region geometry and observed
variability is discussed for a variety of geometries including cylinders,
spheroids, bent, helical and conical jet structures, and intrinsic variability
models including shock excitation. The effects of time delays due to finite
particle acceleration and radiation time scales are also discussed.

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The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
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The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: comp-gas
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
25
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: ao-sci
12
The categories of this paper are: nucl-th