Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic field generation in relativistic shocks - An early end of the
  exponential Weibel instability in electron-proton plasmas   We discuss magnetic field generation by the proton Weibel instability in
relativistic shocks, a situation that applies to the external shocks in the
fireball model for Gamma-ray Bursts, and possibly also to internal shocks. Our
analytical estimates show that the linear phase of the instability ends well
before it has converted a significant fraction of the energy in the proton beam
into magnetic energy: the conversion efficiency is much smaller (of order
m_e/m_p) in electron-proton plasmas than in pair plasmas. We find this estimate
by modelling the plasma in the shock transition zone with a waterbag momentum
distribution for the protons and with a background of hot electrons.
  For ultra-relativistic shocks we find that the wavelength of the most
efficient mode for magnetic field generation equals the electron skin depth,
that the relevant nonlinear stabilization mechanism is magnetic trapping, and
that the presence of the hot electrons limits the typical magnetic field
strength generated by this mode so that it does not depend on the energy
content of the protons. We conclude that other processes than the linear Weibel
instability must convert the free energy of the protons into magnetic fields.

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The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn
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The categories of this paper are: gr-qc
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The categories of this paper are: math
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom