Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A note on stability shifting for the Muskat problem   In this note, we show that there exist solutions of the Muskat problem that
shift stability regimes: they start unstable, then become stable, and finally
return to the unstable regime. We also exhibit numerical evidence of solutions
with medium-sized $L^{\infty}$ norm of the derivative of the initial condition
that develop a turning singularity.

7
The categories of this paper are: hep-th
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The categories of this paper are: gr-qc
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The categories of this paper are: chao-dyn
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: astro-ph
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The categories of this paper are: eess