Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Particle Energy And Acceleration Efficiencies In Highly Relativistic
  Shocks   In this paper we present an investigation of numerical Monte Carlo
simulations of the diffusive shock acceleration in the test particle limit.
Very high gamma flow astrophysical plasmas, have been used, from $\gamma_{up}$
$\sim50$ up to $\gamma_{up}$ $\sim1000$, which could be relevant to the
suggested models of AGNs Jets and their Central Engines as well as the
ultra-relativistic shock particle acceleration in Gamma Ray Burst (GRB)
fireballs. Particularly the energy gain per shock crossing and the time
constant for the above high relativistic processes is numerically calculated.
We explicitly find a considerable $\gamma^{2}$ energy boosting in the first
shock cycle, and in all subsequent shock cycles the particle energy is
multiplied by a large factor. Also a noted acceleration speed-up for the same
acceleration process has been observed. Both of those results are connected
with theoretical suggestions that a significant enhancement of the acceleration
process is possible due to relativistic effects not present at lower plasma
flow speeds. The acceleration speed-up and the mean energy-gain per shock cycle
found could efficiently justify the theory of the origin of Ultra High Energy
Cosmic Rays (UHECR) from the sites of GRBs.

11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc