Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Kinematic Description of Ricci Solitons in Fluid Spacetimes   We consider the kinematics of specific fluid spacetimes admitting timelike
congruences of Ricci Solitons. These fluids includes string cloud, string
fluid, perfect fluid, radially symmetric fluid, anisotropic fluid and
relativistic magneto-fluid. Results are obtained and important physical aspects
are discussed.

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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: supr-con
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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin