Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lagrange coordinates for the Einstein-Euler equations   We derive a new symmetric hyperbolic formulation of the Einstein-Euler
equations in Lagrange coordinates that are adapted to the Frauendiener-Walton
formulation of the Euler equations. As an application, we use this system to
show that the densitized lapse and zero shift coordinate systems for the vacuum
Einstein equations are equivalent to Lagrange coordinates for a fictitious
fluid with a specific equation of state.

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The categories of this paper are: cs
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: funct-an
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The categories of this paper are: physics
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The categories of this paper are: astro-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: math
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: patt-sol