Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Afterglow Light Curves from Impulsive Relativistic Jets with an
  Unconventional Structure   The jet structure in gamma-ray burst (GRB) sources is still largely an open
question. The leading models invoke either (i) a roughly uniform jet with sharp
edges, or (ii) a jet with a narrow core and wide wings where the energy per
solid angle drops as a power law with the angle $\theta$ from the jet symmetry
axis. Recently, a two component jet model has also been considered, with a
narrow uniform jet of initial Lorentz factor $\Gamma_0 \gtrsim 100$ surrounded
by a wider uniform jet with $\Gamma_0 \sim 10-30$. Some models predict more
exotic jet profiles, such as a thin uniform ring (i.e. the outflow is bounded
by two concentric cones of half opening angle $\theta_c$ and $\theta_c +
\Delta\theta$, with $\Delta\theta \ll \theta_c$) or a fan (a thin outflow with
$\Delta\theta \ll 1$ along the rotational equator, $\theta_c = \pi/2 +
\Delta\theta/2$). In this paper we calculate the expected afterglow light
curves from such jet structures, using a simple formalism that is developed
here for this purpose, and could also have other applications. These light
curves are qualitatively compared to observations of GRB afterglows. It is
shown that the two component jet model cannot produce sharp features in the
afterglow model due to the deceleration of the wide jet or the narrow jet
becoming visible at lines of sight outside of it. We find that a "ring" shaped
jet or a "fan" shaped jet produce a jet break in the afterglow light curve that
is too shallow compared to observations, where the change in the temporal decay
index across the jet break is about half of that for a uniform conical jet. For
a "ring" jet, the jet break is divided into two distinct and smaller breaks,
the first occurring when $\gamma\Delta\theta \sim 1-2$ and the second when
$\gamma\theta_c \sim 1/2$.

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The categories of this paper are: funct-an
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The categories of this paper are: cs
2
The categories of this paper are: math
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The categories of this paper are: hep-ph
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
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The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn
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The categories of this paper are: stat
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The categories of this paper are: nlin
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas