Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Acceleration time scale in an ultrarelativistic shock   The acceleration mechanism at ultrarelativistic shocks is investigated using
the Monte Carlo simulations. We apply a method of discrete small amplitude
particle momentum scattering to reproduce highly anisotropic conditions at the
shock and carefully describe the acceleration mechanism. The obtained
acceleration times equal $1.0 r_{g}/c$ if the spectral index reach the value of
2.2, independent of physical conditions in the shock. Some other parameters of
the acceleration process are also provided.

22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
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The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio