Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Physical Model of Delayed Rebrightenings in Shock-interacting
  Supernovae without Narrow Line Emission   Core-collapse supernovae can display evidence of interaction with
pre-existing, circumstellar shells of material by rebrightening and forming
spectral lines, and can even change types as Hydrogen appears in previously
Hydrogen-poor spectra. However, a recently observed core-collapse supernova --
SN 2019tsf -- was found to brighten after roughly 100 days after it was first
observed, suggesting that the supernova ejecta was interacting with surrounding
material, but it lacked any observable emission lines and thereby challenged
the standard supernova-interaction picture. We show through linear perturbation
theory that delayed rebrightenings without the formation of spectral lines are
generated as a consequence of the finite sound crossing time of the post-shock
gas left in the wake of a supernova explosion. In particular, we demonstrate
that sound waves -- generated in the post-shock flow as a consequence of the
interaction between a shock and a density enhancement -- traverse the shocked
ejecta and impinge upon the shock from behind in a finite time, generating
sudden changes in the shock properties in the absence of ambient density
enhancements. We also show that a blastwave dominated by gas pressure and
propagating in a wind-fed medium is unstable from the standpoint that small
perturbations lead to the formation of reverse shocks within the post-shock
flow, implying that the gas within the inner regions of these blastwaves should
be highly turbulent.

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The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: eess
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg