Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rastall gravity is equivalent to Einstein gravity   Rastall gravity, originally developed in 1972, is currently undergoing a
significant surge in popularity. Rastall gravity purports to be a modified
theory of gravity, with a non-conserved stress-energy tensor, and an unusual
non-minimal coupling between matter and geometry, the Rastall stress-energy
satisfying nabla_b [T_R]^{ab} = {\lambda/4} g^{ab} nabla_b R. Unfortunately, a
deeper look shows that Rastall gravity is completely equivalent to Einstein
gravity --- usual general relativity. The gravity sector is completely
standard, based as usual on the Einstein tensor, while in the matter sector
Rastall's stress-energy tensor corresponds to an artificially isolated part of
the physical conserved stress-energy.

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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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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: plasm-ph
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: hep-th
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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: cond-mat
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: cs
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The categories of this paper are: quant-ph