Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radiative cooling in relativistic collisionless shocks. Can simulations
  and experiments probe relevant GRB physics?   We address the question of whether numerical particle-in-cell (PIC)
simulations and laboratory laser-plasma experiments can (or will be able to, in
the near future) model realistic gamma-ray burst (GRB) shocks. For this, we
compare the radiative cooling time, t_cool, of relativistic electrons in the
shock magnetic fields to the microscopic dynamical time of collisionless
relativistic shocks -- the inverse plasma frequency of protons, omega_pp^{-1}.
We obtain that for t_cool*omega_pp^{-1}\lesssim ~few hundred, the electrons
cool efficiently at or near the shock jump and are capable of emitiing away a
large fraction of the shock energy. Such shocks are well-resolved in existing
PIC simulations; therefore, the microscopic structure can be studied in detail.
Since most of the emission in such shocks would be coming from the vicinity of
the shock, the spectral power of the emitted radiation can be directly obtained
from finite-length simulations and compared with observational data. Such
radiative shocks correspond to the internal baryon-dominated GRB shocks for the
conventional range of ejecta parameters. Fermi acceleration of electrons in
such shocks is limited by electron cooling, hence the emitted spectrum should
be lacking a non-thermal tail, whereas its peak likely falls in the multi-MeV
range. Incidentally, the conditions in internal shocks are almost identical to
those in laser-produced plasmas; thus, such GRB-like plasmas can be created and
studied in laboratory experiments using the presently available Petawatt-scale
laser facilities. An analysis of the external shocks shows that only the highly
relativistic shocks, corresponding to the extremely early afterglow phase, can
have efficient electron cooling in the shock transition. We emphasize the
importance of radiative PIC simulations for further studies.

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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: cond-mat
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: chem-ph
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The categories of this paper are: econ
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The categories of this paper are: mtrl-th
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The categories of this paper are: cs
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The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-th