Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radiative transfer in ultra-relativistic outflows   Analytical and numerical solutions are obtained for the equation of radiative
transfer in ultra-relativistic opaque jets. The solution describes the initial
trapping of radiation, its adiabatic cooling, and the transition to
transparency. Two opposite regimes are examined: (1) Matter-dominated outflow.
Surprisingly, radiation develops enormous anisotropy in the fluid frame before
decoupling from the fluid. The radiation is strongly polarized. (2)
Radiation-dominated outflow. The transfer occurs as if radiation propagated in
vacuum, preserving the angular distribution and the blackbody shape of the
spectrum. The escaping radiation has a blackbody spectrum if (and only if) the
outflow energy is dominated by radiation up to the photospheric radius.

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The categories of this paper are: solv-int
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin